false rotary table c plate brands

A drilling rig is not complete without the rotary table, a mechanical device that provides a clockwise rotational force to a drill string and enable the drilling of a borehole. The rotary speed is identified as rpm (rounds per minute) the amount of times the device can complete a full revolution per minute. When the drilling process covers the pipe handling operation in the wellbore, it will require a false rotary table for higher chances of success. Shale Pumps provides this device as a hydraulically driven equipment to seamlessly engage tubulars in a wellbore. We manufacture false rotary tables in-house to ensure precision engineering and the highest-quality design and materials.

When it comes to pipe handling, it is crucial for equipment to be seamless and sturdy to be reliable. Shale Pumps’ false rotary table can handle up to 1.3 million pounds of load while maintaining constant operation at a 20 rpm on maximum speed, making it ideal for long drawn and continuous operations. We developed our false rotary tables, like the SP-FRT375 to perform in the most demanding drilling jobs, and we achieve this only with precision engineering and by using advanced materials.

The false rotary table at Shale Pumps is backed by a guarantee for longevity and trouble-free performance. This way, it outperforms false rotary tables offered by other manufacturers. Our device helps you save money and boost productivity in the long run with lower maintenance costs. Every rotary table equipment has been tested in compliance with the latest industry regulations for safety, efficiency, and quality.

When choosing a false rotary table, be sure that it is being sold by a reputable manufacturer and supplier, like Shale Pumps. That way, you can be sure that the equipment has been manufactured and assembled following a strict and proven format, which ensures its quality. Shale Pumps corrects any material defects and problems with assembly immediately and take note of them to prevent them from occurring again.

Drilling involves pipe handling operations in a wellbore, and this in turn requires a false rotary table, a vital cog in the overall success of the operations. At ShalePumps, the need for constant improvement has resulted in an extensive range of precision engineered equipment, of which the false rotary table occupies the limelight.

This hydraulically driven false rotary table is guaranteed to seamlessly engage the tubulars in the wellbore. Pivotal to drilling operations are the sequence of engaging and lowering tubulars into the wellbore. The false rotary table manufactured at our facility is a fine example of harmony between design, materials and precision engineering.

Featuring a mighty load capacity of 1.3 million pounds operating at a maximum speed of 20 rpm, the false rotary table assists the drilling operations in continuous long drawn operations. Pipe handling requires the seamless and sturdy operation of the false rotary table.

ShalePumps, backed by substantive body of experience and knowhow has developed this high performance false rotary table to ably support drilling operations by incorporating a blend of advanced materials and precision engineering. With a guaranteed long life and trouble free run, the ShalePumps false rotary table spins other models out of reckoning.

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Diversified offers a wide range of Manual Elevators such as Side Door Elevators, Single Joint Elevators, Slip Type Elevators, Safety Clamps and Rotary Slips for 2-3/8” diameter tubing to 30” diameter casing.

Side Door Elevators:Used for handling collar type casing, all of our Side Door Elevators are equipment with a safety latch lock. Our Side Door Elevators come in SLX 150-250 Ton variants from 4-1/2” to 30” OD.

Single Joint Elevators:The SJX Single Joint Elevator is designed for running single joints of tubing and casing from V-door to well center. Our inventory of SJX Single Joint Elevators range from 2-3/8” up to 30”. All comes with load tested Slings and Swivels.

Slip Type Elevators:Our Slip Type Elevators comes in HYC 200 Ton, YT 150 Ton and YC 75 Ton variants. With Slip and Inserts to accommodate 7” Casing down to 2-3/8” Tubing. We can also provide Low Penetrating Dies for Chrome running and handling applications upon request.

Safety Clamps:Used to secure flush tubular products during installation. Our inventory of MP series and Type “C” and “T” Safety Clamps are available from 2-3/8” to 30” OD. We can also provide Low Penetrating Dies for Chrome running and handling applications upon request.

Rotary Slips:Our inventory of Rotary Slips includes SDS, SDML, SDXL and CMS-XL variants from 2-3/8” to 30” OD. We can also provide Low Penetrating Dies for Chrome running and handling applications upon request.

Diversified also offers the following equipment to complete your Casing and Tubing Running Needs: Thread Protectors, Stabbing Guides, Drifts, Bowl & Slips, C-Plate)

Thread Protectors: We offer Air Operated or Clamp-on Type Thread Protectors to offer safe, reliable casing and tubing pin-end protection from 20” casing down to 2-3/8” tubing.

Stabbing Guides:Stabbing Guides are engineered to consistently align and safely guide two sections of pipe together through the use of specially formed polyurethane shells, thereby greatly reducing the chance of pin or box damage. We offer stabbing guides from 13-3/8” casing down to 2-3/8 tubing”.

The C-375 Rotary Table by National Oilwell Varco is used for onshore and offshore drilling. Most conductor, riser, and wellhead elements will pass through the C-375 Rotary Table 37-1/2″ table opening.

Armco produces a full line of NATIONAL Rotaries notable for dependability, safety and efficiency, and suitable for any drilling requirement from shallow to the deepest wells. Construction features of NATIONAL Rotaries are developments of nearly half a century of constant design improvement.

Throughout every region in the world and across every area of drilling and production, our family of companies has provided the technical expertise, advanced equipment, and operational support necessary for success—now and in the future.

We believe in purposeful innovation because we see what others do not and we act. Through business innovation, product creation, and service delivery, we are driven to power the industry that powers the world better.

We believe in service above all because our singular goal is to move our customers’ business forward. This drives us to anticipate our customers’ needs and work with them to deliver the finest products and services on time and on budget.

KET offers Insert bowls to accommodate various casing sizes, Spider Assemblies for tubing and casing, and  Handling Tool Accessories like 2 and 4 Hook and chain / cable slings and false rotary tables.

An extensive database of over 1,700 sound level measurements reported by various references for a wide range of equipment and activities (occupational, recreational, and military noise sources). A reference for each source is provided. The "Intro" tab of this Excel spreadsheet introduces the spreadsheets in which the sound level measurements are organized. This database is compiled by E-A-R/Aero Company and the University of Washington; as of spring 2012, the current version (1.4) is dated 2008.

Eight tables reporting average measurements for noise from equipment used on construction and open sites in the United Kingdom (UK). Organized by construction phase and type; noise level information includes both unweighted octave band Leq levels and overall A-weighted Leq values (in decibels). This document was commissioned by the UK government and published in 2005.

This European Commission database lists operating noise levels for several dozen categories of outdoor equipment. The European Commission requires equipment manufacturers to accompany their equipment with a declaration of conformity, stating that the equipment conforms to the provisions of noise-limiting directives issued by the European Community governing organizations (e.g., Directive 2000/14/EC of the European Parliament and Council, May 8, 2000). Equipment manufacturers continue to add new information to this database in a standard format.

Colgate-Palmolive won the 2012 Safe-in-Sound award through an extensive international effort to reduce noise exposure in its facilities around the world. This online presentation outlines the company"s efforts and successes and presents a summary of numerous adopted engineering modifications (with photos, notes on the changes made, and examples of noise reductions achieved).

This is an online tool for navigating the procurement of low-noise equipment. Part of the NASA EARLAB Auditory Demonstration Laboratory website, the Roadmap can be accessed from the "Buy-Quiet Purchasing" tab in the top navigation menu. Other NASA hearing conservation resources, such as the "Auditory Demonstrations" series and "TWA Calculator," are also part of this website. All are available as free, publicly accessible digital downloadable files. This site is hosted and maintained by Nelson Acoustics as a service to the noise-control and hearing conservation technical community and was updated in 2012.

The website describes itself as follows: "The Roadmap guides users through a stepwise process that includes project planning, researching the marketplace, selecting an achievable noise emission criterion, and developing a specification document. The Roadmap also includes guidelines for identifying the appropriate government procurement strategy for each purchase, based on an assessment of the purchase-specific long-term financial and noise exposure risk. The Roadmap is applicable to both public and private sector organizations, and the downloadable forms and worksheets can be customized to each organization. There is a very brief tutorial PowerPoint presentation here."

NASA"s Roadmap (see entry in the previous section) includes this paper, which provides one alternative methodology for calculating the cost of long-term exposure to the noise emission of various products being considered for a particular purchase. This allows the comparison of the true cost of candidate products that may differ in noise emission and price. Users may input their own experience; for example, as discussed in Appendix G of this chapter, hearing conservation costs vary widely due to factors such as economies of scale, geography, and what elements are included in the calculation). NASA seeks feedback on this methodology in order to continue to improve and update the Roadmap.

Driscoll, D.P. and L.H. Royster. 2003. Chapter 9: Noise Control Engineering. In American Industrial Hygiene Association. The Noise Manual. 5th edition. Edited by E.H. Berger et al. Fairfax, VA: American Industrial Hygiene Association.

This Web page (part of NASA"s Roadmap) lists examples of situations where an acoustical engineer can provide valuable expertise and when a product representative can be useful. The site also describes credentials that acoustical professionals might have.

Industrial hygiene professionals develop hearing conservation programs, conduct noise evaluations, measure sound levels, and perform noise dosimetry. In the box for "Specialty," select "Hearing Conservation/Noise Reduction."

This noise-control materials manufacturer"s website offers general background information on understanding noise-control principles and terminology. Offers continuing education related to noise through the American Institute of Architects.

International scientific society in acoustics dedicated to increasing and diffusing the knowledge of acoustics and its practical applications. Offers continuing education.

Action Level (AL): An 8-hour time-weighted average of 85 decibels, measured on the A-scale, with slow response (equivalently, a dose of 50%). Only sounds 80 dBA and higher are integrated into the AL (the threshold level is 80 dBA).

A-weighting: A measurement scale that approximates the "loudness" of tones relative to a 40-dB sound pressure level, 1,000-Hz reference tone. A weighting is said to best fit the frequency response of the human ear: when a sound dosimeter is set to A-weighting, it responds to the frequency components of sound much like your ear responds. A-weighting has the added advantage of being correlated with annoyance measures and is most responsive to the mid-frequencies, 500 Hz to 4,000 Hz.

B-weighting:B-weighting is similar to A-weighting but with less attenuation. B-weighting was an attempt to approximate human perception of loudness for moderately high sound pressure levels. It is now outdated and no longer used.

C-weighting: A measurement scale that approximates the "loudness" of tones relative to a 90-dB sound pressure level, 1,000-Hz reference tone. C-weighting has the added advantage of providing a relatively "flat" measurement scale that includes very low frequencies.

Criterion level: The continuous equivalent 8-hour A-weighted sound level (as dBA) that constitutes 100% of an allowable noise exposure (dose)--in other words, the permissible exposure limit. For OSHA purposes, this is 90 dB, averaged over 8 hours on the A scale of a standard dosimeter set on slow response.

Dose (%):Related to the criterion level, a dose reading of 100% is the maximum allowable exposure to accumulated noise. For OSHA, 100% dose occurs for an average sound level of 90 dBA over an 8-hour period (or an equivalent exposure). If a TWA reading is used rather than the average sound level, the time period is no longer explicitly needed. A TWA of 90 dBA is the equivalent of 100% dose. The dose doubles every time the TWA increases by the exchange rate. Table A-1 shows the relationship between dose and the corresponding 8-hour TWA exposure.

Example: OSHA uses an exchange rate of 5 dBA. Suppose the TWA is 100 dB for an 8-hour exposure. The dose doubles for each 5-dB increase over the criterion level of 90 dBA. The resulting dose is therefore 400%. With an 8-hour TWA of 80 dBA, the dose would halve for each 5 dBA below the criterion level. The resulting dose would be 25%. When taking noise samples of duration shorter than the full workday, dose is an easy number to work with because it is linear with respect to time.

Example: If a 0.5-hour screening sample results in 9% dose and the workday is 7.5 hours long, the estimated dose for the full workday would be 135% (7.5 ÷ 0.5 × 9%). This is computed making the assumption that the sampled noise will continue at the same levels for the full 7.5-hour workday. While short-term dose measurements cannot be used to support a citation, they can be effectively used as a screening tool to determine whether full-shift sampling is warranted.

Example: A worker is employed in a high noise area for half an hour each day, and the remainder of the 8-hour workday is spent in a quiet office area. If the worker is exposed to 93 dBA for half an hour, the dosimeter will read 10%. Because no additional dose will be accumulated while working in the quiet office area, the equivalent 8-hour TWA will be 73.4 dBA, as shown in Table A-1.

** Additional data points are provided in Table A-1 in Appendix A, Section II of the noise standard (29 CFR 1910.95), particularly in the 80-999% dose range.

Exceedance level: The level exceeded by the measured noise level for an identified fraction of time. Exceedance levels may be calculated for many time fractions over the course of a shift and are typically expressed with percentages (L%). For example, an L40 equal to 73 dBA would mean that for 40% of the run time, the decibel level was higher than 73 dBA.

Exchange rate (or doubling rate):The increase or decrease in decibels corresponding to twice (or half) the noise dose. For example, if the exchange rate is 5 dBA, 90 dBA produces twice the noise dose that 85 dBA produces (assuming that duration is constant). The OSHA exchange rate is 5 dBA (see Table D-2 of the construction noise standard, 29 CFR 1926.52, and Tables G-16 and G-16a of the general industry noise standard, 29 CFR 1910.95).

Only instruments using a 5-dBA exchange rate may be used for OSHA compliance measurements. CSHOs should be aware that the following organizations use noise dosimeters with a 3-dBA exchange rate: NIOSH, EPA, ACGIH, and most foreign governments. The U.S. Department of Defense (DOD) previously used a 4-dBA exchange rate; however, all branches (except the U.S. Navy) now have adopted the 3-dBA exchange rate.

Impulsive or Impact noise: Impulsive or impact noise is characterized by a sharp rise and rapid decay in sound levels and is less than 1 second in duration.

Intensity of sound: Intensity of sound is measured in watts per square meter. To calculate the intensity level in decibels, find the ratio of the intensity (I) of sound to the threshold intensity (I0).

Lavg (or LAVG): The average sound level measured over the run time of measurement. This becomes a bit confusing when thresholds are used, because the average does not include any sound below the threshold. Sound is measured in the logarithmic scale of decibels, so the average cannot be computed by simply adding the levels and dividing by the number of samples. When averaging decibels, short durations of high levels can significantly contribute to the average level.

Example: Assume the threshold is set to 80 dBA and the exchange rate is 5 dBA (the settings of OSHA"s Action Level). Consider taking a 1-hour noise measurement in an office where the A-weighted sound level was typically between 50 dBA and 70 dBA. If the sound level never exceeded the 80-dBA threshold during the 1-hour period, then the LAVG would not indicate any reading at all. If 80 dBA was exceeded for only a few seconds due to a telephone ringing near the instrument, then only those seconds will contribute to the LAVG, resulting in a level perhaps around 40 dBA (notably lower than the actual levels in the environment).

Ldn (or LDN):Representing the day/night sound level, this measurement is a 24-hour average sound level, where 10 dB is added to all of the readings taken between 10 p.m. and 7 a.m. This is primarily used in community noise regulations where there is a 10-dB "penalty" for nighttime noise but is not used to evaluate compliance with OSHA standards, as it is not an occupational issue.

Leq: The true equivalent sound level measured over the run time. LEQ is functionally the same as LAVG, except that it is only used when the exchange rate is set to 3 dB and the threshold is zero.

Max level: The highest weighted sound level that occurred, also allowing for the response time to which the meter is set. If the meter is set for A-weighting with slow response, the max level is the highest A-weighted sound that occurred when applying the slow response time.

Noise dosimeter: A type of sound level meter that measures and integrates noise over time providing a value of the average dose. This instrument can calculate the daily noise dose based on a full workshift of measurements, or a dose from a shorter sample. The operator can select different noise dose criteria, exchange rates, and thresholds.

Octave bands: Sounds that contain energy over a wide range of frequencies are divided into sections called bands, each one octave. A common standard division is in 10 octave bands identified by their center frequencies, 16; 31.5; 63; 250; 500; 1,000; 2,000; 4,000; 8,000, and 16,000 Hz. For each octave band, the frequency of the lower band limit is one-half the frequency of the upper band limit. This is the most common type of frequency analysis performed for workplace exposure evaluation and control. An alternative frequency band, the one-third octave band, is defined as a frequency band such that the upper band-edge frequency, f2, is the cube root of two times the lower band frequency, f1: f2 = (2)1/3f1. The level of detail provided by one-third octave bands, however, is rarely required for occupational noise evaluation and control.

Peak noise: The highest instantaneous sound level that a microphone detects. Unlike the max level, the peak is detected independently of the slow or fast response for which the unit is set.

Example: The peak circuitry is very sensitive. Test this by simply blowing across the microphone. You will notice that the peak reading may be 120 dB or greater. When you take a long-term noise sample (such as a typical 8-hour workday sample for OSHA compliance), the peak level is often very high. Because brushing the microphone over a shirt collar or accidentally bumping it can cause such a high reading, the user must be careful not to place too much emphasis on the reading.

Permissible exposure limit (PEL): An 8-hour time-weighted average of 90 decibels, measured on the A-scale, with slow response (equivalently, a dose of 100%). Only sounds 90 dBA and higher are integrated into the PEL (the threshold level is 90 dBA).

Receiver:A person exposed to noise that originates at a noise source. If the receiver is exposed to a hazardous noise level, the exposure can be reduced through various noise-control methods.

Response: Instruments that measure time-varying signals are limited in how fast they can respond to changes in the input signal. Sound dosimeters can operate with a wide variety of response times, but the industry has chosen two particular response times to standardize measurements. These are known as the slow and fast response times. OSHA, the Mine Safety and Health Administration, and ACGIH all require the slow response for sound dosimetry. The standardized time constant for the slow response is 1 second.

Sound level meter:An instrument that converts sound pressure in air into corresponding electronic signals. The signals may be filtered to correspond to certain sound weightings (e.g., A-weighted scale, C-weighted scale).

Threshold level: The A-weighted sound level at which a personal noise dosimeter begins to integrate noise into a measured exposure. For example, if the threshold level on a sound level meter is set at 80 dBA, it will capture and integrate into the computation of dose all noise in the worker"s hearing zone that equals or exceeds 80 dBA. Sound levels below this threshold would not be included in the computation of noise dose. Use an 80-dBA threshold for measurements related to hearing conservation programs and a 90-dBA threshold for exposure results related to the need for engineering or administrative controls.

The hypothetical exposure situations shown in Table A-2 illustrate the relationship between criterion level, threshold, and exchange rate and show the difference of using a dosimeter with an 80-dBA threshold versus a 90-dBA threshold to characterize a worker"s noise exposure. For example, an instrument with a 90-dBA threshold will not capture any noise below that level and will thus give a readout of 0%, even if the worker being measured is actually being exposed to 89 dBA for 8 hours (i.e., to 87% of the allowable noise dose over any 8-hour period).

Time-weighted average (TWA): A constant sound level lasting 8 hours that would result in the equivalent sound energy as the noise that was sampled. TWA always averages the sampled sound over an 8-hour period. This average starts at zero and grows. It is less than the Lavg for a duration of less than 8 hours, is exactly equal to the Lavg at 8 hours, and grows higher than the Lavg after 8 hours.

Example: Think of a TWA as having a large 8-hour container that stores sound energy. If you run a dosimeter for 2 hours, your Lavg is the average level for those 2 hours-consider this a smaller 2-hour container filled with sound energy. For TWA, take the 2-hour container and pour that energy into the 8-hour container. The TWA level will be lower. Again, TWA is always based on the 8-hour container. When measuring using OSHA"s guidelines, TWA is the proper number to report if the full workshift was measured.

Type 1/Type 2 (or Class 1 and Class 2): Two different accuracy specifications for noise measurements. Type 1 measurements are accurate to approximately ±1dB and Type 2 measurements are accurate to approximately ±2dB. The accuracy of the measurements varies, however, depending on the frequency of the sound being measured.

Z-weighting: An unweighted measurement scale that does not apply any attenuation or weighting to any frequency. Instead, this scale provides a flat response across the entire spectrum from 10 Hz to 20,000 Hz, making it useful for octave band analysis and evaluating engineering controls.

The human ear can hear a broad range of sound pressures. Because of this, the sound pressure level (Lp) is measured in decibels (dB) on a logarithmic scale that compresses the values into a manageable range. In contrast, direct pressure is measured in pascals (Pa). Lp is calculated as 10 times the logarithm of the square of the ratio of the instantaneous pressure fluctuations (above and below atmospheric pressure) to the reference pressure:

Where P is the instantaneous sound pressure, in units Pa, and Pref is the reference pressure level, defined as the quietest noise a healthy young person can hear (20 µPa).

Sound power level (Lw) is similar in concept to the wattage of a light bulb. In fact, Lw is measured in watts (W). Unlike Lp, Lw does not depend on the distance from the noise source. The sound power level is calculated using the following equation:

Decibels are measured using a logarithmic scale, which means decibels cannot be added arithmetically. For example, if two noise sources are each producing 90 dB right next to each other, the combined noise sound pressure level will be 93 dB, as opposed to 180 dB. The following equation should be used to calculate the sum of sound pressure levels, sound intensity levels, or sound power levels:

Often, using this equation to quickly sum sound levels when there is no calculator or computer available is difficult. The following table can be used to estimate a sum of various sound levels:

Example: There are three noise sources immediately adjacent to one another, each producing a sound pressure level of 95 dB. The combined sound level can be found using the table above. The difference between the first two noise sources is 0 dB, which means the sum will be 95 + 3 = 98 dB. The difference between 98 dB and the remaining noise source (95 dB) is 3, which means the sum will be 98 + 2 = 100 dB.

Under the OSHA PEL, workers are not permitted to be exposed to an 8-hour TWA equal to or greater than 90 dBA. OSHA uses a 5-dBA exchange rate, meaning the noise level doubles with each additional 5 dBA. The threshold to measure noise is 90 dBA when determining compliance to the PEL. The following chart shows how long workers are permitted to be exposed to specific noise levels:

The values in the chart above are from Table G-16 in the general industry standard, 29 CFR 1910.95. To calculate a permissible duration that is not addressed in this chart, use the following equation:

A worker"s daily noise exposure typically comes from multiple sources, which have different noise levels for different durations. When adding different noise levels from various noise sources, only noise levels exceeding 90 dBA should be considered. The combined effect of these noise sources can be estimated using the following equation:

Where Cnis the total duration of exposure at a specific noise level, and Tn is the total duration of noise permitted at that decibel level. If the sum equals or exceeds "1," the combined noise level is greater than the allowable level. If the sum is less than "1," the combined noise level is less than the allowable level.

Example: A worker in a machine shop is exposed to 95 dBA for 2 hours, 69 to 78 dBA for 4 hours (including a 15-minute break and 45-minute lunch), and 90 dBA for 3 additional hours.

To determine if the worker"s noise exposure exceeds a 90 dBA TWA, use the previous equation. Because the noise levels in the break room (69 dBA) and parts department (78 dBA) are below the 90 dBA threshold, these periods of the day are not included in the calculation. According to the chart above, workers are permitted to be exposed to 95 dBA for 4 hours per day and 90 dBA for 8 hours per day. Calculate the ratio of actual exposure duration to permissible exposure duration for each time segment and add them: 2/4 + 3/8 = 7/8. The resulting value (7/8) is less than 1; therefore, this worker"s exposure does not exceed the 90 dBA PEL. However, a separate calculation would be required to determine if a hearing conservation program is required, and this evaluation would utilize an 80 dBA threshold.

Occasionally, it is necessary to convert a set of octave band sound pressure levels into an equivalent A-weighted sound level. This is easily done by applying the A-scale correction factors for the nine standard octave center frequencies and combining the corrected values by decibel addition (see B.3 above). The A-scale correction factors are the values of the A-weighting network at the center of each particular octave band. The value derived by combining the corrected values for each octave band is designated the A-weighted sound level (dBA).

If a sound is generated at a point source in a free field, meaning there are no walls or other obstructions, the sound pressure level, Lp, will be reduced by 6 dB each time the distance from the noise source is doubled. Alternatively, Lp will increase by 6 dB in a free field each time the distance to the noise source is halved. Consider the following example:

Example: A worker is surveying an open field, which has a diesel generator running in the middle of it. The worker is 100 ft from the generator and is exposed to a noise level of 85 dBA. When the worker is 25 ft from the generator, the noise level will be 97 dBA. At 200 ft from the generator the worker will be exposed to a noise level of 79 dBA.

Calculating the sound pressure level at a specific distance from a noise source is often useful. The following equation allows one to calculate the sound pressure level at any distance from a noise source in a free field:

Where Lpd2 is the sound pressure level at the new distance from the noise source, Lpd1 is the sound pressure level at the original distance, d1 is the original distance, and d2 is the new distance.

Example: The sound pressure level of an aircraft engine in the middle of an open runway is 120 dBA at a distance of 50 ft from the receiver. The sound pressure level at a distance of 80 ft is calculated using the equation above. Lpd1 is 120 dBA, d1 is 50 ft, and d2 is 80 ft. Therefore, Lpd2 is 120 + 20 × log(50/80), which is 116 dBA.

Using the LAVG equation from B.7, note the case for an eight-hour shift (T = 8 hr), which by definition LAVG = TWA, resulting in the following equation. Note that this is the TWA to Dose conversion formula, as contained in 1910.95 App A:

Example: A factory hires a health and safety consultant to measure the noise exposure of the workers. The consultant writes a report that states that workers are exposed to 183% Dose, according to the general industry standard, 29 CFR 1910.95. Convert this Dose into an 8-hour TWA.

The Occupational Noise Exposure standard requires employers implement a hearing conservation program whenever worker noise exposures equal or exceed an 85 dBA TWA, or a 50% dose, also known as the “Action Level” (AL). The LAVG equation in B.7 can be used to calculate the AL in dBA for any work shift length (T), and using a Dose = 50%, as follows (also see OSHA Standard Interpretation, 1982):

Using the above equation for various shift lengths T, the Action Level values in Table B-9.1 are obtained. Note that each value in the “Uncorrected” column in Table B-9.1 represents a 50% Dose, as shown.

Instrument accuracy must be taken into account when making compliance determinations. Type-2 dosimeters are considered to have an error of ±2 dBA, and the Action Level must be corrected, accordingly. For example, for an 8-hour shift, the corrected Action Level would be 87 dBA (85 + 2 dBA). Using the Dose equation from B.8, the Dose representing a TWA of 87 dBA can be calculated, resulting in a Dose of 66%, as follows:

Therefore, a TWA exposure equal to or exceeding 87 dBA or a Dose of 66%, as measured by the instrument, would require compliance with the hearing conservation requirements of the noise standard.

Table B-9.1 also shows each Action Level corrected for instrument error, by adding 2 dBA to each value. Also, each corrected AL (dBA) can be converted to Dose using the Dose equation from B.7, where LAVG = AL, and inputting the appropriate time period, T. This results in a Dose of 66% for each time period. These values are shown in the “Corrected” column in Table B-9.1.

Note that compliance with the AL for extended workshifts can be determined using any of the following parameters: Dose, TWA, or adjusted AL. See Section IV.E. for more information and examples.

Ultrasound is any sound whose frequency is too high for the human ear to hear. (The upper frequency that the human ear can detect is approximately 15 to 20 kilohertz, or kHz, although some people can detect higher frequencies, and the highest frequency a person can detect normally declines with age.) Most of the audible noise associated with ultrasonic sources, such as ultrasonic welders or ultrasonic cleaners, consists of subharmonics. Even though the ultrasound itself is inaudible, the subharmonics it generates can affect hearing and produce other health effects.

Research indicates that ultrasonic noise has little effect on general health unless there is direct body contact with a radiating ultrasonic source. Reported cases of headache and nausea associated with airborne ultrasonic exposures appear to have been caused by high levels of audible noise from source subharmonics.

Subharmonics are sound waves with frequencies that are a fraction (e.g., one-half, one-quarter) of the original ultrasound frequency. Because they are lower than the ultrasound, the human ear can detect them.

The American Conference of Governmental Industrial Hygienists (ACGIH®) has established permissible ultrasound exposure levels. These recommended limits (set at the middle frequencies of the one-third octave bands from 10 kHz to 100 kHz) are designed to prevent possible hearing loss caused by the subharmonics of the set frequencies, rather than the ultrasound itself. These exposure levels represent conditions under which it is believed that nearly all workers may be repeatedly exposed without adverse effects on their ability to hear and understand normal speech. (Table C-1)

ACGIH also offers recommendations for measuring or verifying ultrasound levels, which requires a precision sound level meter equipped with a suitable microphone of adequate frequency response and a third-octave filter. CSHOs considering evaluating ultrasound levels should consult the CTC for assistance in selecting a suitable instrument.

Subjective annoyance and discomfort may occur at levels between 75 and 105 dB for the frequencies from 10 kHz to 20 kHz especially if they are tonal in nature. Hearing protection or engineering controls may be needed to prevent subjective effects. Tonal sounds in frequencies below 10 kHz might also need to be reduced to 80 dB. (ACGHI, 2020)

b These values assume that human coupling with water or other substrate exists, and may be raised by 30 dB when there is no possibility of such coupling.

For additional information on ultrasound exposure levels, ceiling values, and 8-hour TWAs that apply to other frequencies, as well as ceiling values measured underwater, refer to the complete ACGIH TLV for ultrasound (see ACGIH, 2020, Threshold Limit Values for Chemical Substances and Physical Agents & Biological Exposure Indices).

High-frequency noise is highly directional and is associated with short wavelengths. This means that it is easily reflected or blocked by any type of barrier. The wavelength of a 16-kHz tone, for example, is about 3/4 inch. A modest barrier, extending just 1 to 2 inches beyond the source, is generally sufficient to reflect noise of approximately the same frequency away from a nearby worker. High-frequency audible noise is also easily absorbed by many acoustical materials, such as glass fiber or foam.

Over the past decades, several countries have set exposure limits or recommended levels for ultrasound at various frequencies. The differences in limits are great and reflect differences in the interpretation and analysis of studies on ultrasound and human health. Table C-2 lists ceiling values measured in air in dB, as opposed to 8-hour TWAs or ceiling values measured in water in dB. Though ultrasonic frequencies are not audible to the human ear, it is clear that the international community is concerned about the effects that subharmonic frequencies have on human health.

For a detailed review of ultrasound effects on human hearing, published literature, international ultrasound standards, and recommendations for future directions, see:

The report concludes: There is not sufficient data in the literature to support, or even contemplate, a dose response relation between occupational exposure to VHF noise and resultant hearing risk.

Ototoxic substances came gradually to the attention of occupational health and safety professionals in the 1970s, when the ototoxicity of several industrial chemicals, including solvents, was recognized. The possibility of noise/solvent interaction was raised more recently, when Bergström and Nyström (1986) published the results of a 20-year epidemiological follow-up study in Sweden, started in 1958 and involving regular hearing tests in workers. Interestingly, a large proportion of workers employed in the chemicals divisions of companies suffered from hearing impairment, although noise levels were significantly lower than those in sawmills and paper pulp production. The authors suspected that industrial solvents were an additional causative factor in hearing loss.

Workers are commonly exposed to multiple agents. Physiological interactions with some mixed exposures can lead to an increase in the severity of harmful effects. This applies not only to the combination of interfering chemical substances, but also in certain cases to the co-action of chemical and physical factors. In this case, effects of ototoxic substances on ear function can be aggravated by noise, which remains a well-established cause of hearing impairment.

According to the European Agency for Safety and Health at Work (2009), experiments with rats have shown that combined exposure to noise and solvents induced synergistic adverse effects on hearing. "Good evidence" has been accumulated on the adverse effects on hearing of the following solvents:

The rat cochlea is sensitive to aromatic solvents, unlike that of the guinea pig or chinchilla (Campo et al., 1993; Cappaert et al., 2003; Davis et al., 2002; Fechter, 1993). These findings have been attributed to metabolic and other toxicokinetic differences (Campo and Maguin, 2006; Davis et al., 2002; Gagnaire et al., 2007). Because of their metabolism, rats are considered comparatively good animal models for the investigation of the ototoxic properties of aromatic solvents in humans (Campo and Maguin, 2006; Kishi et al., 1988).

Investigators suggest that exposure to these solvents can provoke irreversible hearing impairment, with the cochlear hair cells (organ of Corti) being considered a target tissue for these solvents (Figure 5; Campo et al., 2007).

Scanning electron micrograph of a rat organ of Corti prior to (left panel) and after (right panel) toluene exposure (from European Agency for Safety and Health, 2009, as published in Lataye et al., in 1999).

Although the cochlea suffers damage, particularly during co-exposure, recent studies have reported that solvents reduce the protective role played by the middle-ear acoustic reflex, an involuntary muscle contraction that normally occurs in response to high-intensity sound stimuli. A disturbance of this reflex would allow more acoustic energy into the inner ear (Campo et al., 2007; Lataye et al., 2007; Maguin et al., 2009).

A number of epidemiological studies have investigated the relationship between hearing impairments and co-exposure to both noise and industrial solvents (Chang et al., 2003; De Barba et al., 2005; Johnson et al., 2006; Kim et al., 2005; Morata, 1989; Morata et al., 1993, 2002; Morioka et al., 2000; Prasher et al., 2005; Sliwinska-Kowalska et al., 2003, 2005). Due to confounding factors, straightforward conclusions could not easily be drawn from these studies. However, the evidence of additive or synergistic ototoxic effects due to combined exposure to noise and solvents is very strong (Lawton et al., 2006; Hoet and Lison, 2008).

A longitudinal study (Schäper et al., 2003; Schäper et al., 2008) on the relationship between hearing impairment measured by pure tone audiometry and occupational exposure to toluene and noise has not found ototoxic effects in workers exposed to a concentration of toluene lower than 50 ppm. The observed hearing loss was associated only with noise intensity. However, the use of hearing protection was not taken into account in the conclusions relative to the potential interaction between noise and toluene on hearing.

A clear relationship between solvent and hearing impairment is difficult to assess through the available epidemiological studies. The workplace environments where noise and solvents can be simultaneously present are typically complex (for example, see critical review of Lawton et al., 2006; Hoet and Lison, 2008). Quite often, the workers were exposed to multiple substances. Furthermore, most of these studies had a cross-sectional design that featured a number of weaknesses in the interpretation of the findings. For instance, chronic effects were related to currently measured exposures. In some cases, the exposure concentrations measured at the time of the study were markedly lower than those ascertained in past years (Morata et al., 1993).

All in all, there are limited data on dose-response relationships or clear effects on auditory thresholds in humans (for reviews, see Lawton et al., 2006; Hoet and Lison, 2008). However, animal data clearly show an effect. Further human studies are needed for clarification of these issues. However, in the interim, one cannot rule out a likely relationship between solvent exposure and hearing impairments.

Overall, in combined exposure to noise and organic solvents, interactive effects may be observed depending on the parameters of noise (intensity, impulsiveness, frequency, duration, etc.) and the solvent exposure concentrations. In cases of concomitant exposures, animal studies suggest that solvents might exacerbate noise-induced impairments even though the noise intensity is below the permissible limit value.

European Agency for Safety and Health. 2009. Combined Exposure to Noise and Ototoxic Substances. [Reproduction of this report is authorized, provided the source is acknowledged.]

4To put this exposure level in perspective, 29 CFR 1910.1000, Table Z-2, lists OSHA’s 8-hour TWA PEL for styrene as 100 ppm, with a 200 ppm peak, and up to 600 ppm permitted for no more than 5 minutes in a 3-hour period.

Bergström, B. and B. Nyström. 1986. Development of Hearing Loss During Long-Term Exposure to Occupational Noise--A 20-Year Follow-up Study. Scand. Audiol.15: 227-34.

Brandt-Lassen, R., S.P. Lund, and G.B. Jepsen. 2000. Rats Exposed to Toluene and Noise May Develop Loss of Auditory Sensitivity Due to Synergistic Interaction. Noise Health 3(9): 33-44.

Campo, P. and K. Maguin. 2006. Solvent-Induced Hearing Loss: Mechanisms and Prevention Strategy. International Workshop on Health Effects of Exposure to Noise and Chemicals--Ototoxicity of Organic Solvents. Nofer Inst. of Occup. Med., Lodz, Poland, November 15-16 (conference report).

Campo, P., K. Maguin, and R. Lataye. 2007. Effects of Aromatic Solvents on Acoustic Reflexes Mediated by Central Auditory Pathways. Toxicol. Sci. 99(2): 582-90.

Cappaert, N.L., S.F. Klis, H. Muijser, B.M. Kulig, and G.F. Smoorenburg. 2001. Simultaneous Exposure to Ethylbenzene and Noise: Synergistic Effects on Outer Hair Cells. Hear. Res. 162(1-2): 67-79.

Cappaert, N.L., S.F. Klis, H. Muijser, B.M. Kulig, L.C. Ravensberg, and G.F. Smoorenburg. 2003. Differential Susceptibility of Rats and Guinea Pigs to the Ototoxic Effects of Ethyl Benzene. Neurotoxicol. Teratol. 24: 503-10.

Cary, R., S. Clarke, and J. Delic. 1997. Effects of Combined Exposure to Noise and Toxic Substances--Critical Review of the Literature. Ann. Occup. Hyg. 41(4): 455-65.

CDC-HHE. 2011. Centers for Disease Control--Health Hazard Evaluation Report, Noise and Lead Exposures at an Outdoor Firing Range--California, HETA 2011-0069-3140, September.

CDC-NIOSH. 2018. Centers for Disease Control—National Institute for Occupational Safety and Health, Safety and Health Information Bulletin. Preventing Hearing Loss Caused by Chemical (Ototoxicity) and Noise Exposure. SHIB 03-08-2018, DHHS (NIOSH) Publication No. 2018-124.

Chang, S.J., T.S. Shih, T.C. Chou, C.J. Chen, H.Y. Chang, and F.C. Sung. 2003. Hearing Loss in Workers Exposed to Carbon Disulfide and Noise. Environ. Health Perspect. 111: 1620-24.

Davis, R.R., W.J. Murphy, J.E. Snawder, C.A. Striley, D. Henderson, A. Khan, and E.F. Krieg. 2002. Susceptibility to the Ototoxic Properties of Toluene Is Species Specific. Hear. Res. 166(1-2): 24-32.

De Barba, M.C., A.L. Jurkiewicz, B.S. Zeigelboim, L.A. De Oliveira, and A.P. Bellé. 2005. Audiometric Findings in Petrochemical Workers Exposed to Noise and Chemical Agents. Noise Health 7(29): 7-11.

Johnson, A.C., L. Juntunen, P. Nylén, E. Borg, and G. Höglund. 1988. Effect of Interaction Between Noise and Toluene on Auditory Function in the Rat. Acta Otolaryngol. 105: 56-63.

Johnson, A.C., T.C. Morata, A.C. Lindblad, P.R. Nylén, E.B. Svensson, E. Krieg, A. Aksentijevic, and D. Prasher. 2006. Audiological Findings in Workers Exposed to Styrene Alone or in Concert With Noise. Noise Health 8: 45-57.

Kishi, R., I. Harabuchi, T. Ikeda, H. Yokota, and H. Miyake. 1988. Neurobehavioural Effects and Pharmacokinetics of Toluene in Rats and Their Relevance to Man. Br. J. Ind. Med.45: 396-408.

Lacerda A., Lerous T, Morata T. 2005. Ototoxic effects of carbon monoxide exposure: a review; Pro-Fono Revista de Atualizacao Cientifica, Barueri (SP), v. 17, n.3, p. 403-412, set.-dez.

Lataye, R. and P. Campo. 1997. Combined Effects of a Simultaneous Exposure to Noise and Toluene on Hearing Function. Neurotoxicol. Teratol. 19: 373-82.

Lataye, R., P. Campo, G. Loquet, and G. Morel. 2005. Combined Effects of Noise and Styrene on Hearing: Comparison Between Active and Sedentary Rats. Noise Health 7(27): 49-64.

Lawton, B.W., J. Hoffmann, and G. Triebig. 2006. The Ototoxicity of Styrene: a Review of Occupational Investigations. Int. Arch. Occup. Environ. Health 79: 93-102.

Lund, S.P. and G.B. Kristiansen. 2008. Hazards to Hearing from Combined Exposure to Toluene and Noise in Rats. Int. J. Occup. Med. Environ. Health 21(1): 47-57.

Maguin, K., P. Campo, and C. Parietti-Winkler. 2009. Toluene Can Perturb the Neuronal Voltage-Dependent Ca2+ Channels Involved in the Middle-Ear Reflex. Toxicol. Sci. 107(2): 473-81.

Mäkitie, A.A., U. Pirvola, I. Pyykkö, H. Sakakibara, V. Riihimäki, and J. Ylikoski. 2003. The Ototoxic Interaction of Styrene and Noise. Hear. Res. 179(1-2): 9-20.

Morata, T.C., D.E. Dunn, L.W. Kretschmer, G.K. Lemasters, and R.W. Keith. 1993. Effects of Occupational Exposure to Organic Solvents and Noise on Hearing. Scand. J. Work Environ. Health 19: 245-54.

Morata, T.C., A.C. Johnson, P. Nylen, E.B. Svensson, J. Cheng, E.F. Krieg, A.C. Lindblad, L. Ernstgard, and J. Franks. 2002. Audiometric Findings in Workers Exposed to Low Levels of Styrene and Noise. J. Occup. Environ. Med. 44: 806-14.

Morioka, I., N. Miyai, H. Yamamoto, and K. Miyashita. 2000. Evaluation of Combined Effect of Organic Solvents and Noise by the Upper Limit of Hearing. Ind. Health. 38(2): 252-7.

Prasher, D., H. Al-Hajjaj, S. Aylott, and A. Aksentijevic. 2005. Effect of Exposure to a Mixture of Solvents and Noise on Hearing and Balance in Aircraft Maintenance Workers. Noise Health 7(29): 31-9.

Schäper, M., P. Demes, M. Zupanic, M. Blaszkewicz, and A. Seeber. 2003. Occupational Toluene Exposure and Auditory Function: Results From a Follow-up Study. Ann. Occup. Hyg. 47: 493-502S.

Schäper, M., A. Seeber, and C. van Thriel. 2008. The Effects of Toluene Plus Noise on Hearing Thresholds: an Evaluation Based on Repeated Measurements in the German Printing Industry. Int .J. Occup. Med. Environ. Health 21: 191-200.

Sliwinska-Kowalska, M., E. Zamyslowska-Szmytke, W. Szymczak, P. Kotylo, M. Fiszer, W. Wesolowski, and M. Pawlaczyk-Luszczynska. 2003. Ototoxic Effects of Occupational Exposure to Styrene and Co-exposure to Styrene and Noise. J. Occup. Environ. Med. 45: 15-24.

Sliwinska-Kowalska, M., E. Zamyslowska-Szmytke, W. Szymczak, P. Kotylo, M. Fiszer, W. Wesolowski, and M. Pawlaczyk-Luszczynska. 2005. Exacerbation of Noise-Induced Hearing Loss by Co-exposure to Workplace Chemicals. Environ. Tox. Pharmacol. 19: 547-53.

In reviewing IMIS data, note that the exposure levels are not necessarily typical of all worksites and occupations within an industry. Rather, IMIS provides insight regarding the noise exposure levels for workers in the jobs that OSHA monitored while visiting workplaces. Typically, OSHA identified those jobs as having some potential for noise exposure.

Workplace noise exposure is widespread. Historical analysis of OSHA"s Integrated Management Information System (IMIS) data for 1979 through 2006 showed that workers were exposed to hazardous noise levels in every major industry sector.

OSHA obtained the vast majority of IMIS noise exposure samples in manufacturing facilities. Manufacturing is among the loudest industries, with 43% of the IMIS noise samples exceeding the PEL of 90 dBA TWA. In addition, 47% of the samples taken in the construction industry exceeded the PEL. The IMIS exposure records for the manufacturing industry are presented by three-digit North American Industrial Classification System (NAICS) codes in two tables (Tables E-3 and E-4) (relative to the AL and PEL, respectively).

In addition to median dBA and percent over the PEL, Table E-4 shows the distribution of manufacturing industry dosimetry measurements at the PEL and higher (by dBA level).

1 This period encompasses the entire IMIS record for noise through 2006. The data were first inspected, and individual records with internal inconsistencies were removed. One example of an inconsistency is a record coded as a personal noise result with units other than dB or percentage dose (e.g., a value coded as a noise result with units inadvertently entered as mg/m3 would have been removed before analysis). The final dataset contained 224,339 personal noise exposure records.

2 Please note that workplace sampling is required, and the historical data displayed should not be used to justify whether or not to monitor for overexposure to noise.

Noise is a potential hazard for most jobs that involve abrasive or high-power machinery, impact of rapidly moving parts (product or machinery), or power tools. According to IMIS noise measurements, workers in certain occupations within specific industries are exposed to excessive noise more frequently than others. While many jobs have noise exposure, historically, some of the occupations with the most extreme exposures (listed by Standard Industrial Classification, or SIC) have included:

SIC 22, 23, and 31 (textile, apparel, and leather industry): textile winders, shoe and leather workers and repairers, textile knitting and weaving machine operators.

SIC 28 through 30 (printing and publishing, chemicals and petroleum, and plastics and rubber industries): chemical equipment operators (SIC 28 and 29), laborers and freight movers (SIC 28 and 29), grinding machine operators (SIC 30), and helpers (SIC 30).

SIC 32 (nonmetallic minerals industry): inspectors, testers, and sorters; extruding, forming, and pressing machine operators; hoist and winch operators; unspecified "operators."

SIC 33 and 34 (primary metal and fabricated metal products industries): forging machine operators, grinding and lapping machine operators, and welders.

SIC 35 through 39 (various equipment manufacturers): milling and planing machine operators, coil winders and tapers, forging machine operators, grinding and lapping machine operators, and abrasive blasters.

Research conducted by the University of Washington provided information on noise exposures in the construction industry. This data is provided in Tables E-5 and E-6 below.

When OSHA promulgated its Hearing Conservation Amendment in 1983, it incorporated the EPA labeling requirements for hearing protectors (40 CFR 211), which required manufacturers to identify the noise reduction capability of all hearing protectors on the hearing protector package. This measure is referred to as the noise reduction rating (NRR). It is a laboratory-derived numerical estimate of the attenuation achieved by the protector. It became evident that the amount of protection users were receiving in the workplace with the prescribed hearing protectors did not correlate with the attenuation indicated by the NRR. OSHA acknowledged that in most cases, this number overstated the protection afforded to workers and required the application for certain circumstances of a safety factor of 50% to the NRR, above and beyond the 7 dB subtraction called for when using A-weighted measurements. For example, consider a worker who is exposed to 98 dBA for 8 hours and whose hearing protectors have an NRR of 25 dB. We can estimate the worker’s resultant exposure using the 50% safety factor. The worker’s resultant exposure is 89 dBA in this case.

The 50% safety factor adjusts labeled NRR values for workplace conditions and is used when considering whether engineering controls are to be implemented.

Dual hearing protection involves wearing two forms of hearing protection simultaneously (e.g. earplugs and ear muffs). The noise exposure for workers wearing dual protection may be estimated by the following method: Determine the hearing protector with the higher rated NRR (NRRh) and subtract 7 dB if using A-weighted sound level data. Add 5 dB to this field-adjusted NRR to account for the use of the second hearing protector. Subtract the remainder from the TWA. It is important to note that using such double protection will add only 5 dB of attenuation. For a more extensive discussion of how to use the NRR, see the NIOSH website. NIOSH has developed guidelines for calculating and using the NRR in various circumstances (Hearing Protector Devices ). Also see 29 CFR 1910.95 Appendix B.

Use the following formulas to estimate the attenuation afforded to a noise-exposed employee in a work environment by muffs, plugs, or a combination of both.

When applying the 50% safety factor for estimating field attenuation (required when considering whether engineering controls are to be implemented), the above equations are modified as follows:

Workers can be overexposed to noise when they wear communications headsets as part of their work. Clerical personnel, aircraft pilots and other cockpit personnel, air traffic controllers, emergency personnel, reservation clerks, receptionists, and telephone operators are just a few examples of the more than 3 million workers who can be exposed to high noise levels via communications headsets. For a person wearing a sound-generating headset, the sound/noise exists predominantly between the eardrum and the headset. Because of the amplification properties of the human ear, the sound that exists inside the ear while wearing a headset is quite different from ambient levels.

Probe microphones and similar devices allow sound levels to be measured inside the ear. In addition, there are other methods that can be used to monitor these types of exposures. CSHOs can contact the OSHA Salt Lake Technical Center, Health Response Team, for more information and assistance.

Most modern telecommunication headsets use sophisticated limiting circuits. Some personal audio headsets also have this capability. Headsets with acoustic limiting devices that are functioning as designed have been shown, in both laboratory and field tests, to provide enough protection to keep worker noise exposures below OSHA permissible noise levels. In some work environments, however, headsets without limiting devices have caused worker noise exposures to exceed the levels permitted by OSHA.

Several sources have offered detailed methods for evaluating the feasibility of engineering controls for noise. These methods involve diverse interpretations of how the costs of noise exposure are calculated, based on the individual needs of the organization for which the method was developed. They also include various additional steps and tools to help refine the organization"s priorities or to help standardize the process. This appendix reviews five possible approaches for evaluating the benefits and costs of noise control:

American Industrial Hygiene Association (AIHA)--Benefits and Costs of Noise Control. In: The Noise Manual (AIHA, 2003; or latest edition); in the 2003 edition, see Chapter 9, "Noise Control Engineering"

Note that other methods for performing economic feasibility analyses may be available, and CSHOs should refer to regional/national office enforcement personnel for guidance, as necessary.

Dollar amounts quoted in this section are relative estimates, used as examples to demonstrate methods for determining whether implementing a hearing conservation program or engineering controls is more economical. Actual costs will vary based on factors such as location, availability of supplies, and varying cost inflation. The CSHO should investigate local costs in situations where the relative cost differential is close, as determined following this procedure.

In 2001, OSHA Region III produced an instruction on conducting economic feasibility evaluations for noise-control engineering. This instruction (Directive Number STD 104.1A) was based in part on information published in the Regulatory Impact and Regulatory Flexibility Analysis of the Hearing Conservation Amendment, OSHA Office of Regulatory Analysis, February 1983.

This section presents information adapted from the Region III instruction. The assumptions and tables contain examples of approximate costs and other related information. This information is used here to demonstrate (through examples) some simple methods that CSHOs can use when considering economic feasibility of engineering controls compared to a hearing conservation program. The numbers used in these assumptions, tables, and examples should be refined as appropriate for each inspection and locality.

Assumption 1: If actual life expectancy of equipment is known to the CSHO, then it should be used. If unknown, assume the life expectancy of durable-equipment engineering noise control is 10 years. Regardless of the source of the life expectancy figure, use it to determine the average cost per year (i.e., total lump sum upfront costs for equipment divided by years of life expectancy).

Assumption 2: If actual costs for an engineering control are known to the CSHO, then they should be used. If costs for an item listed in Table H.1-2 are unknown, the average cost in Table H.1-2 shall be used for cost estimating.

Assumption 3: The maintenance cost for an engineering control shall not exceed 5% of the initial cost per year over a 10-year time span (based on guidance from the Office of the President of the United States, OMB).

Assumption 4: If actual maintenance costs for an engineering control are known to the CSHO, then they should be used. If unknown, then the percentage given in Table H.1-2 shall be used for cost estimating.

Assumption 5: The least expensive control option or group of controls that will achieve a reduction of 3 dBA or more in worker exposure shall be used for determining economic feasibility.

Assumption 6: An engineering or administrative control is economically feasible if its total cost is less than or equal to the cost of a continuing effective hearing conservation program for all the workers who would benefit from the control"s implementation (i.e., have a reduction in their noise exposure).

Assumption 7: If actual costs of administrative controls are known to the CSHO, then they should be used. Where administrative controls are feasible but the costs are unknown, no additional costs will be assumed for cost estimation purposes.

Assumption 8: If the actual cost of a production penalty for a control option is known to the CSHO, then it should be used. If unknown, no production penalty will be assumed for cost estimation purposes.

Assumption 9: If a proposed noise control would also address another hazard (e.g., machine guarding, local exhaust ventilation, etc. hood), then the cost of the noise control shall be deemed feasible because these other controls do not require an economic feasibility analysis.

Assumption 10: If actual hearing conservation program costs are known to the CSHO, then they should be used. If unknown, use an assumed figure of $375/worker/year (the average of the range provided in Appendix G.1.2 of this chapte