Hearing Conservation Program
Even though we cannot see sound, it is a force with real dimensions and definite properties: intensity and duration. Intensity is the loudness of a sound, or the pressure it exerts through the ear. It is measured in units called decibels (dB). In assessing noise, a special measure called "dBA" indicates damage to hearing The higher the dBA number, the greater the risk of damage to hearing.
Sound intensity, also known as acoustic intensity, is defined as the power carried by sound waves per unit area in a direction perpendicular to that area. Some examples of sound intensities are listed below.
- Table Saw 110-115 dB
- Router 110-115 dB
- Band Saw 100 dB
- Hand Power Saw 110-115 dB
- Planer 110-115 dB
- Chop-Saw 90-95 dB
- Power Drill 95 dB
- Grinder 100-110 dB
- Steam Cleaner 95 dB
- Forklift 90 dB
- Road Grader 90-95 dB
- Front End Loader 90-95 dB
- Riding Mower 95-100 dB
- Weed Trimmer, Gas 95-100 dB
- Chain saw 110 dB
- Shotgun 12 GA 140 dB
Note these are not actual figures merely examples. Actual noise levels may vary by manufacturer and condition/maintenance of machinery or equipment.
Duration is the amount of time you are exposed to a sound level. The table below indicated how much noise you can be exposed to in a certain time period. For example. You can be exposed to a noise level of 90 dba for up to 8 hours a day. Temporary hearing loss was taken into consideration to determine the exposure levels. For example, should you be exposed to a noise level of 100 dBA for two hours, the remaining 22 hours of that day's exposure should be at a noise level below 90 dBA This recovery period varies, depending upon the individual, the severity and length of exposure.
Permissible noise exposure scale based on the OSHA Noise Standard
Duration - hours per day sound level (dBA)
1/4 or less150
Warning Signs of Over-Exposure to Noise
Temporary threshold shift (TTS)
Tinnitus (ringing in the ears)
Although many people experience one or both is is difficult to detect unless a hearing test is performed by a license Audiologist.
With repeated exposure, the effects are cumulative. It is the need to prevent this cumulative damage that drives hearing protection programs. If you suspect that you are being exposed to excessive levels of noise, contact EH&S. We can perform 8-hour time-weighted monitoring as well as spot measurement of noise levels to determine what level of protection is appropriate to protect your hearing.
Types of Hearing Protectors
There are different types of hearing protectors. These range from the type of hearing protectors ranging from disposable to custom fit protectors. These hearing protectors reduce the intensity of the noise that enters the ear canal thus protecting your hearing.
Noise Reducing Rating
To determine what the rating your hearing protectors are. You can look at the manufacture Label on the package that the equipment came from to see what the noise reducing rating is. In the below example, the noise-reducing rating is 33 decibels for this specific piece of equipment. If you are using a piece of equipment that produces noise that is 150 decibels the effectiveness of the noise protector will be 120 decibels. if using the equipment for an 8-hour period the hearing protectors will not be sufficient. To further reduce the hearing protector a different type of hearing protector can be use or combination of hearing protectors can be used to reduce the amount of noise to 90 decibels. For example, if the rating of disposable hearing protectors is 33 decibels and a pair earmuff has a rating of 30 decibels then you would have a noise reducing rating of 63 decibels.