This session is part of the training required under our Hearing Conservation Program. The Occupational Safety and Health Administration, or OSHA, requires a Hearing Conservation Program whenever employees are exposed to noise levels that equal or exceed an 8-hour time-weighted average sound level of 85 decibels.

This training session will cover:

• The impact of noise on your hearing;
• Advantages and disadvantages of hearing protection devices;
• The use, care, and fit of hearing protection devices; and
• The need for hearing—or “audiometric”—tests and what to expect when you have these tests.

Session Objectives

Here are the main objectives of this training session. You will be able to:

• Understand the effects of noise on your hearing;
• Identify the sources of potentially hazardous noise in your workplace;
• Describe the purpose of audiometric testing, and be able to interpret your test results; and
• Select, fit, and use hearing protection.

What Is Sound?

First let’s discuss the basics of sound and noise, so that you better understand why certain kinds of noise can be hazardous.

• Sound is a longitudinal pressure wave of energy with two important characteristics: frequency and pressure.

– Frequency, or pitch, is measured in hertz, or cycles per second. The human ear can hear between a range of 20 to 20,000 hertz. The human voice is normally in the range of 500 to 2,000 hertz.

– Pressure is what determines the loudness of a sound, and it is measured in decibels. A whisper is approximately 10 dB, while the noise of a chain saw is approximately 100 dB.

• The frequency and pressure of a sound wave, together with the duration of exposure to this wave, determine the risk of hearing loss and other noise hazards. The longer you are exposed to noise, the greater your chances of hearing damage.

Noise Sources

There is a wide variety of noise sources in a typical workplace.

• Machinery, tools, and equipment emit sounds of varying loudness and in a particular range of frequencies.
• Noise sources may be continuous, like most machines, or they may be intermittent, like a punch press or a jackhammer.
• Low-frequency noise sources, such as vibrating equipment, are particularly hazardous. They can cause hearing loss in speech frequencies—that is, your ears can lose their ability to hear what other people are saying.

Think about the sources of noise in your workplace, such as machinery or power tools, and whether they are continuous or intermittent.

Sound Pressure Levels of Common Noises

This slide shows the sound pressure levels of different common sources of noise:

• A whisper is at 10 decibels.
• A normal conversation is at 65 decibels.
• Shop tools are around 90 decibels.
• Pneumatic drills, woodworking machinery, blasting, and jackhammers can be at 100 decibels or more.

You risk hearing damage when you are exposed to more than about 90 decibels over an 8-hour period without hearing protection. A sound level of 140 decibels for any length of time is considered to be very dangerous to your hearing. Note from the list how many common workplace noise sources are more than 90 decibels.

OSHA Noise Exposure Limits

OSHA requires different exposure limits, depending on the loudness of the sound; the louder the noise, the less time for exposure is permitted. For example:

• 8 hours of exposure is permitted for noise of 90 decibels, while
• Only 4 hours is permitted for noise of 95 decibels.
• As noise goes up by 5 decibels, the permissible exposure limit is cut in half.
• 100 decibels time weighted average or “TWA” for 2-hour exposure.
• 105 decibels TWA for 1-hour exposure.

When these limits are reached, we try to reduce exposure to noise by using engineering and administrative controls. Hearing protection is used if these controls are not effective or cannot be put into place.

Indicators of High Noise Levels

You can generally tell when noise levels are close to or go beyond permissible exposure limits. Noisy conditions make normal conversation difficult, or impossible.

• At 80 decibels, people have to speak very loudly to be heard.
• At 85 to 90 decibels, people need to shout in order to be understood.
• And at 95 decibels, people have to move very close together in order to be able to hear each other at all.

How Is Noise Hazardous?

How can noise be hazardous to your health and safety?

• First, noise can cause temporary or permanent hearing loss.
• Noise can cause you to misunderstand communication with co-workers. This could cause you to do something that causes an accident.
• Similarly, noise can cause you to miss important safety warnings, such as if a co-worker tries to warn you of a nearby hazard.
• Finally, noise creates stress that can affect you both physically and mentally.

How We Hear Sounds

To understand how noise can be harmful, we first need to understand how we hear sounds.

• Sound waves enter the ear canal and travel until they strike the eardrum.
• The vibrations of the eardrum are passed along by tiny bones— sometimes referred to as the hammer, anvil, and stirrup—into the inner ear.
• The vibrations cause tiny hairlike cells in the inner ear to move back and forth, similar to a field of grass being moved by a gust of wind.
• Finally, the moving cells stimulate the auditory nerve that sends a “sound” signal to your brain.

How Hearing Is Damaged

This slide explains how hearing can be damaged by loud noise.

• Our ability to hear depends on the small, delicate parts in the middle ear or inner ear—especially the hairlike cells in the inner ear.
• When functioning normally, these cells lie flat when exposed to loud noise. When the noise stops, the cells spring back. But over a long period of exposure to loud noise, the cells take longer and longer to spring back, until they eventually are too damaged to return to their normal position. People who say that noise doesn’t bother them may in fact be losing their hearing function, so noise does not seem as loud.
• Hearing loss is gradual, and most often is caused by long-term damage to the cells in the inner ear.
• Once hearing damage happens, it is usually permanent and cannot be regained.

Hearing Loss

• “Hearing loss” is any reduction in your ability to hear sounds, compared with that of a person with normal hearing who is about your same age.
• There are two types of hearing loss:

– Temporary hearing loss (known as temporary threshold shift) may occur immediately following exposure to a very loud noise. In this type of hearing loss, because the damage to the ear is only temporary, the ability to hear normally is restored after a few hours.

– Permanent hearing loss (known as standard threshold shift) is the result of permanent damage to the inner ear. This type of hearing loss cannot be restored.

Signs of Hearing Loss

Signs of hearing loss are often difficult to notice because hearing loss is usually very gradual and is not painful. Here are some of the signs that you should be alert to:

• Difficulty in hearing people speak. Do you find yourself asking people to speak up or to repeat what they have said because you couldn’t hear them?
• Inability to hear certain high-pitched or soft sounds. You may have trouble hearing the ticking of a clock or a watch.
• Noise or ringing in one or both ears.
• Getting complaints from others that the volume of the radio or TV is too high.

Can you think of someone you know who has experienced hearing loss? Think of the signs that this person may have shown that indicated hearing loss.

Evaluating Noise Exposure Hazard

To know whether there is a risk of hearing damage in the workplace, we must first evaluate the noise exposure to see if it is hazardous.

• The first step is to conduct a noise survey. This identifies and characterizes sources of high noise, and it identifies employees who may be impacted by high noise levels.
• Next, we monitor the noise exposure of employees who may be impacted. Typically, a “noise dosimeter” is used. The dosimeter records all noise levels and computes the average noise exposure for each employee. The readings from one employee may be also used for other employees who have similar jobs.
• Finally, we repeat the noise monitoring whenever there is a change in production, process, or equipment that may change noise levels.

Noise Hazards – Any Questions?

Do you understand the information that has been presented about noise hazards? Now it’s time to ask yourself if you understand:

• The hazards of noise and how to identify these hazards;
• The signs and symptoms of hearing loss; and
• Measuring hearing loss.

It is important for your safety that you understand how excessive noise can affect your hearing and the symptoms of hearing loss.

Elements of the Hearing Conservation Program

The Hearing Conservation Program is intended to help protect you from hearing damage and hearing loss. Here are the basic elements of our Hearing Conservation Program:

• All employees who are exposed to 85 decibels or more over 8-hour periods must participate in the program.
• As a participant, you receive:

– A baseline and an annual audiogram, which measures your hearing;

– Annual training on hearing loss and hearing protection

• Hearing protection will be provided to you.
• Finally, we will continue to conduct noise exposure assessments, especially when our operations change, to accurately assess our employees’ exposure to noise.

Audiometric Exams

Audiometric exams, or audiograms, are an important part of our Hearing Conservation Program.

• These exams can detect early signs of hearing loss.
• An audiometric exam typically measures hearing ability in each ear, and finds your threshold for hearing six different sound frequencies—500, 1,000, 2,000, 3,000, 4,000, and 6,000 hertz.
• These hearing thresholds are compared with previous audiograms to determine if there has been a “threshold shift,” or a loss of hearing, at any of the frequencies.

Standard Threshold Shift (STS)

What is a Standard Threshold Shift, or STS?

• A hearing loss has occurred if you have experienced an STS during your annual audiogram. The STS may be slight, moderate, or severe.
• Specifically, an STS will be found if your threshold for hearing has increased by an average of 10 decibels or more at 2,000, 3,000, and 4,000 hertz in either ear from your baseline audiogram. Your age is also a factor in evaluating whether an STS has occurred. If an STS is detected, you will be notified within 21 days.
• Changes in the hearing protection you use may be required if you have an STS. You may be asked to start wearing hearing protection if you have not done so previously. Or if you have been wearing hearing protection, you may be asked to start using a different kind.

Because hearing loss may be caused by other factors besides noise, such as illnesses or injuries, you may also be required to have further medical evaluation.

Has an STS Occurred?

• Take a few moments to study this graph. Does it show that an STS has occurred? (Pause for a few seconds.)
• Yes, the graph shows that the average threshold shift in the 2,000, 3,000, and 4,000 hertz frequencies is more than 10 decibels when compared against the baseline.

An Example of Hearing Loss in Carpenters

This graph shows an example of hearing loss experienced by carpenters who are exposed to high noise levels. Take a few moments to study the graph. The 55-year-old carpenter has experienced severe hearing loss, especially at the 3,000, 4,000, and 6,000 hertz levels, and would have a great deal of difficulty understanding anyone who is speaking at a normal level.

• The 25-year-old carpenter has already experienced some hearing loss at the high frequencies, so that his hearing is about equal to a 50-year-old who has not been exposed to high noise levels.

Hearing Protection Use

To protect against hearing loss, the use of hearing protection is required by OSHA under different conditions of noise exposure.

• Hearing protection use is voluntary for employees who are exposed to an 8-hour time weighted average of 85 to 90 decibels.
• Use of hearing protection becomes mandatory when:

– There is exposure to an 8-hour time weighted average of 90 decibels or higher; or

– There is exposure to an 8-hour time weighted average of 85 decibels when an STS, or hearing loss, has already been measured, or if a baseline hearing test has not yet been conducted.

Individual companies may have requirements for wearing hearing protection that are stricter than OSHA’s requirements.

Hearing Protection Devices Noise Reduction

Hearing protection devices reduce your exposure to noise. Here is what these devices are expected to achieve.

• Hearing protection devices must reduce noise exposure to below an 8-hour time weighted average of 90 decibels.
• For employees who have suffered an STS, hearing protection must reduce exposure to less than an 8-hour TWA of 85 decibels.
• The noise reduction ratio, or “NRR,” is the number of decibels that different types of hearing protection devices are rated to reduce noise exposure. However, the NRR is only what is achieved through laboratory testing, rather than in real-world applications. Therefore, you should assume that the real-world NRR of a hearing protection device will be significantly less than what may be shown on the package, due to such variables as poor fit or incorrect use.

– For example, for earplugs, you should assume that the real-world NRR is no better than one-third of the NRR shown on the package.

– For earmuffs, assume that the real-world NRR is no better than about one-half the NRR shown on the package.

Note that removing your hearing protection device for short periods during the day will further reduce the real-world NRR of the device. Always wear your hearing protection when you are in noisy locations.

Hearing Protection Devices – Earplugs and Canal Caps

Two of the most commonly used hearing protection devices are earplugs and canal caps.

• There are many different brands of earplugs, but they all work in a similar way. Typically, you roll or compress the foam plug into a cylinder, insert it in your ear, and allow the foam to expand and fill the ear canal. Earplugs are effective protection against noise and are lightweight and unobtrusive. Make sure that the plugs are clean before inserting them in your ear. You should get a new pair of earplugs each day, or more frequently if necessary.
• Canal caps can be useful if you are exposed to loud noise for short periods of time, or if you need to walk through a noisy area to get from one place to another. Canal caps usually do not provide the same degree of protection as earplugs because they do not enter the ear canal.
• Cotton balls are not effective as hearing protection, and should not be used.

Hearing Protection Devices – Earmuffs

Earmuffs are hearing protection devices that are usually used in combination with earplugs to reduce noise exposure even further. However, they must fit correctly and form a good seal, or they might actually increase noise exposure by creating an “echo” effect inside the earpiece. Note that headphones from radios or CD players do not count as earmuffs or hearing protection devices.

Here are some guidelines for using earmuffs:

• The muffs must be sealed against the head and fully enclose the ears.
• Hair should be pulled out and away from earmuffs.
• Glasses and caps should not interfere with the seal.
• The headband should be adjusted so that the cushions exert even pressure.
• Finally, earmuffs should be cleaned periodically with warm, soapy water and rinsed thoroughly.

Any Questions?

It is time to ask yourself if you understand the information presented so far.

Do you understand:

• Audiometric testing;
• Our hearing protection program;
• When to use hearing protection; or
• Different types of hearing protection devices.

It is important for your safety that you understand how to protect your hearing.

Key Things to Remember

Here are the key things to remember about this training session on noise and hearing conservation:

• First, your hearing is a very important sense—don’t lose it.
• Noise exposure of 85 decibels or more can cause hearing loss.
• Hearing loss cannot be cured or repaired.
• Hearing tests that are conducted annually can detect hearing loss, so that steps can be taken to prevent further hearing loss.
• Finally, hearing protection devices must be worn in high-noise areas in accordance with our company’s rules.

This concludes the training session on Noise and Hearing Conservation.