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Course 751 - Hearing Conservation Program Management

Safety guides and audits to make your job as a safety professional easier
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Sound levels
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Evaluating Exposures

Warning Signs of Hazardous Noise

Noise may be a problem in your workplace if:

  • You hear ringing or humming in your ears when you leave work.
  • You have to shout to be heard by a co-worker an arm's length away.
  • You experience temporary hearing loss when leaving work.

Noise-induced hearing loss can develop rapidly in workers exposed to relatively high noise levels on a daily basis.

1. Which of the following is TRUE regarding noise-induced hearing loss?

a. It affects women more often than men
b. It can develop rapidly
c. It is always temporary
d. It is extremely rare

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Evaluating Exposure to Noise

The first step toward solving any noise problem is to define it.

The first step toward solving any noise problem is to define it. The easiest way to determine if the level of noise in your workplace might be hazardous is to talk with someone in the noisy area of the workplace. If you can talk comfortably with someone 3 feet away, there is probably not enough plant noise at that position to damage hearing. But if you must shout to be heard or understood from a distance of between 1-3 feet, noise at that position may cause hearing loss, and you should have the sound levels evaluated.

A noise problem in the workplace may be evaluated in using two basic strategies:

  1. By analyzing the subjective responses of employees who are disturbed by the noise; and
  2. By objective measurements of the sound levels and comparison of those values with noise regulations or noise criteria generally regarded as applicable to the situation.

2. Sound levels should be measured in the workplace if _____.

a. you must yell at someone working outside the building
b. you must shout to be heard or understood from a distance of 1-3 feet
c. you can't hear others talking to you from a distance of 5 feet or greater
d. others are disturbed when you yell at them

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Evaluating Noise (Continued)

When noise levels are between 85 and 90 dB, people have to shout.
If you have to shout, you probably need measure sound levels.

Subjective Responses

There are various factors that may indicate noise is a problem in the workplace. While people react differently to noise, subjective responses should not be ignored because they may provide warnings that noise may be at unacceptable levels.

Noisy conditions can make normal conversation difficult.

  • When noise levels are above 80 decibels (dB), people have to speak very loudly.
  • When noise levels are between 85 and 90 dB, people have to shout.
  • When noise levels are greater than 95 dB, people have to move close together to hear each other at all.

Objective Measurements

Objective measurements are made in accordance with some relatively precise set of instructions, usually based on laws and regulations. In the usual industrial noise situation, there will be two types of objective measurements:

  1. Compliance measurements, which are made in accordance with some relatively precise set of instructions, usually based on laws or regulations. The purpose is usually to determine the extent of compliance with the limits set forth OSHA 1910.95, Occupational nose exposure. In an OSHA noise exposure compliance survey, the basic data will be the slow A-weighted sound levels measured using dosimeters at the ear location of the workers, together with the times spent at the sound levels encountered. From these data, the daily noise dose is calculated by means specified in the regulations.
  2. Diagnostic measurements, which are used in engineering control of noise to help locate specific noise sources and determine their magnitudes, and to help select the types of controls needed, their locations, and the amount of reduction sought.

3. At what noise level (db) does it become difficult to hear someone when they speak at a normal volume?

a. 30 dB
b. 65 dB
c. 80 dB
d. 105 dB

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Noise Survey Instruments

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SLMs take one-time readings.

There are two different instruments to measure noise exposures: the sound level meter and the dosimeter.

Sound Level Meter (SLM)

A SLM is a device that measures the intensity of sound at a given moment. Since sound level meters provide a measure of sound intensity at only one point in time, it may be necessary to take a number of measurements at different times to estimate noise exposure over a workday.

A SLM typically consists of a microphone, a calibrated attenuator, a stabilized amplifier, an indicating meter, and the designated weighting networks. Two types of SLMs are commonly used in the workplace:

Type 1 SLM. The Type 1 meter has an accuracy of +1 dBA and is preferred for the design of cost-effective noise controls.

Type 2 SLM. A Type 2 meter is has an accuracy of +2 dBA and meets the minimum requirement by OSHA for noise measurements. It is usually sufficient for general purpose noise surveys. It is usually less bulky, lighter, and less expensive than the Type 1 SLM.

SLMs can be used to:

  • Spot-check noise dosimeter performance.
  • Determine the employee's noise dose whenever use of a noise dosimeter is unavailable or inappropriate.
  • Identify and evaluate individual noise sources for abatement purposes.
  • Aid in determining the feasibility of engineering controls for individual noise sources.
  • Evaluate hearing protectors.

Please click here to learn more about the considerations of use for SLMs.

4. Which sound level meter meets minimum OSHA standards but is less accurate?

a. Type 1
b. Type 2
c. Type 3
d. Type 4

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Noise Survey Instruments


Hierarchy of Controls gsg image
Dosimeters measure noise over time to obtain a time-weighted average reading.

A dosimeter is like a sound level meter except that it stores sound level measurements providing a time-weighted average (TWA) noise exposure reading typically for an 8-hour workday. Because OSHA requires noise readings over time, the noise dosimeter is the primary meter used for compliance measurements.

With a dosimeter, a microphone is attached to the employee's clothing, and the exposure measurement is simply read at the end of the desired time period. A reader may be used to read-out the dosimeter's measurements. Since the dosimeter is worn by the employee, it measures noise levels in those locations in which the employee travels.

A sound level meter can also be positioned within the immediate vicinity of the exposed worker to obtain an individual exposure estimate. Such procedures are generally referred to as "personal" noise monitoring.

Dosimeters can be used to:

  • Make compliance measurements according to OSHA's noise standard.
  • Measure the employee's exposure to noise and automatically compute the necessary noise dose calculations.

Click here to learn more about the considerations of use for dosimeters.

5. According to OSHA's noise standard, what is the primary instrument for making compliance measurements?

a. Acoustic limited devices
b. Octave band analyzers
c. Audio equalizer
d. Noise dosimeter

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Noise Surveys

Tour the facility and develop a detailed understanding of potential noise sources.
Tour the facility and develop a detailed understanding of potential noise sources.

Noise surveys should be performed walking around the workplace to screen for employee noise exposures and to determine if additional monitoring is necessary. When screening for noise exposures, it is sufficient to take measurements using a sound level meter, and estimate the duration of exposure. The resulting spot readings can be used to determine the need for a more thorough evaluation using dosimeters. The following general approach may be followed:

  1. Tour the facility and develop a detailed understanding of facility operations and potential noise sources. Make notes on a diagram of the floor plan if possible. Look for indications that noise may be a problem.
  2. Use a sound level meter to take spot readings of operations that are in question. It may be useful to mark the sound levels on a diagram of the floor plan. Make notes regarding what equipment is on or off.
  3. Estimate 8-hour time-weighted average (TWA) exposures by identifying workers and their locations, and estimate the length of time they spend in different areas or how long they operate particular equipment or tools.

If the results of the survey indicate an estimated 8-hour TWA exposures of 80 dBA or more, then additional noise monitoring should be performed.

6. What is the purpose of a noise survey?

a. To determine if additional exposure monitoring is necessary
b. To fix a time when the workplace is beyond limits
c. To log the percentage of non-compliance
d. To analyze the acoustics in various work areas

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A dosimeter is small enough that it should not interfere with an employee's duties.
A noise dosimeter should not interfere with an employee's duties. Image used with permission from Sensidyne

Work-shift Sampling

When the results of the noise survey indicate that noise levels may exceed those listed in 1910.95, additional monitoring using dosimeters is necessary. Establish a sampling protocol for your workplace. You can follow this sampling protocol:

  1. Explain the purpose of the dosimeter to each employee being sampled and emphasize that the dosimeter is not a speech recording device.
  2. Inform the employee being monitored that the dosimeter should be placed so that it does not interfere with work, and emphasize that the employee should continue to work as usual.
  3. Instruct the employee being sampled not to remove the dosimeter unless absolutely necessary and not to cover the microphone with a coat or outer garment or move it from its installed position. Inform the employee when and where the dosimeter will be removed.
  4. Place the microphone in the employee's hearing zone. OSHA defines the hearing zone as a sphere with a two-foot diameter surrounding the head. Most manufacturers recommend that the microphone be placed on the shoulder area midway between the head and the point of the shoulder. Practicality and safety will dictate the actual microphone placement at each survey location.
  5. Use the microphone windscreen to protect the microphone when the wearer is outdoors or in dusty or dirty areas (the windscreen will not protect the microphone from rain or extreme humidity).
  6. When noise levels are different at each of the employee’s ears, the higher level must be sampled.
  7. Position and secure any excess microphone cable to avoid snagging or inconvenience to the employee. If practical, the cord should be run under the employee's shirt or coat.
  8. Check the dosimeter periodically to ensure the microphone is properly oriented.
  9. Obtain and note sound level meter readings during different phases of work the employee performs during the shift. It is important to take enough readings to identify task work cycles. For statistical reasons, more readings should be taken when noise levels fluctuate widely.
  10. Record the information required on the OSHA-92 Noise Survey Report.

7. Which instrument is used to determine the average noise exposure to which a worker is exposed during the workshift?

a. Sound calibration meter
b. Microphone
c. Noise dosimeter
d. Sound level meter

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Employee potentially overexposed to noise.
Noise overexposure in the workplace can occur where employees wear a communications headset as part of their employment.

Employees Wearing Headsets are at Risk

Noise overexposure in the workplace can occur where employees wear a communications headset as part of their employment. 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 three million workers who can be exposed to high noise levels via communication's headsets.

When is sound too loud in earphones and headphones?

Use this test to determine if a co-worker might be exposed to excessive sound levels while using earphones. If you can hear the sound being delivered into a person's ear via headphones or earphones, it indicates the sound is too loud and can eventually lead to permanent hearing loss.

8. What does it indicate if you can hear the music in a co-worker's earphones?

a. The music contains too much noise
b. The music must be turned off
c. The music must be hard rock
d. The music is too loud and harmful

Check your Work

Read the material in each section to find the correct answer to each quiz question. After answering all the questions, click on the "Check Quiz Answers" button to grade your quiz and see your score. You will receive a message if you forgot to answer one of the questions. After clicking the button, the questions you missed will be listed below. You can correct any missed questions and check your answers again.


Dawson Sound Level Meter Training Video

3M Edge Dosimeter Training Video

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