Hearing conservation: The difference between “noise” and “sound”
Hearing conservation is all about keeping your ears safe at work, especially in industries or jobs where there's a lot of noise.... or is it sound? Preventing hearing loss before it starts and preserving the hearing you have requires understanding the difference between noise and sound.
Simply put, sound is what we hear while noise is unwanted, unpleasant, or harmful sound. Prolonged exposure to noise, particularly at high decibel levels, can lead to hearing loss which can be permanent and debilitating. Industries that are especially susceptible to harmful noise include construction, manufacturing, forestry, transportation, and entertainment.
Interpreting the OSHA standard
Workers who are exposed to noise at or above determined limits are at risk of developing significant and permanent hearing loss over their work life if they are not adequately protected. OSHA’s occupational noise standard, 1910.95, has established two levels of exposure, averaged over an 8-hour time period, at which employers must take steps to protect workers.
- Action level (AL) – at or above 85 dB or an equivalent of 50% dose, employers must:
- Implement a hearing conservation program that includes noise monitoring;
- Provide annual audiograms and appropriate follow-ups for exposed workers;
- Enforce use of hearing protective devices (HPDs) when engineering or administrative controls are not sufficient to reduce exposure to acceptable limits; and
- Deliver effective annual employee training.
- Permissible exposure level (PEL) – at or above 90 dB or an equivalent 100% dose, employers must:
- Implement engineering or administrative controls to reduce noise exposure;
- Enforce the use of HPDs when engineering or administrative controls are not sufficient to reduce exposure to acceptable limits; and
- Evaluate noise regularly to determine when ALs may require further action.
Here is a quick tip! If you need to raise your voice to speak to someone only 3 feet away, it’s likely the noise level is over OSHA’s action level of 85 decibels.
Understanding the parameters of sound
Noise is considered hazardous based on how loud the sound is, how long it lasts, and how often the exposure is. For hearing conservation, noise monitoring factors in these measurements:
- Frequency – the “pitch” of sound, measured in Hertz (Hz) and representing the number of sound waves passing a particular point per second. The higher the frequency, the higher the pitch as with a high-pitched whistle.
- Amplitude – the loudness or intensity of sounds, measured in decibels (dB). The larger the amplitude, the louder the sound as with speakers at a concert.
- Time – the duration of sound, or how long it lasts. Keep in mind that at both long-lasting and short duration, high amplitude sounds can be damaging to your hearing.
Identifying types of sound
For proper hearing protection, employers must account for several different noise types including:
- Continuous – noise that lasts for more than one second and is stable over time. The hum of an air conditioner or fan is an example of continuous noise.
- Intermittent – noise that cycles on and off with quiet periods in between. Intermittent noise may include a pump or generator kicking on or off as needed, an airplane flying overhead, and many manufacturing noises.
- Impulse – noise created by the collision of two masses with a duration of less than one second. Common examples of impulse noise include alarm systems, jackhammers, or punch presses.
- Impact – noise with an amplitude over 130 dB that has a sharp rise and rapid decline. Gunshots, explosions, and popping balloons are examples of impact noise.
By understanding the parameters of sound, including its intensity, frequency, and the three types - intermittent, continuous, and impulse - we can better manage noise exposure and protect our hearing.
Keys to remember: Sound is what we hear; noise is harmful or unpleasant sounds. Understanding sound types, intensities, and frequencies helps protect and preserve hearing now and into the future.