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Hearing Protection


If you value your hearing, it's important to protect it. There are different types of protection. Each has their own pros and cons. This page will cover the basics.

Attenuation:
The unit of measure for sound pressure level is the decibel. Hearing protection is rated in the level of reduction of the sound level (attenuation) from the ambient sound pressure level (SPL). If one hearing protection reduces the level 30dB (dB = decibels) and another reduces it by 20dB, the one that reduces it by 30dB will protect you better.

The audio spectrum for humans is stated as 20Hz (Hertz - unit of measure for frequency - number of cycle per second) to 20,000Hz. This, however, is a bit optimistic for most people. From my experience, 30Hz-16kHz is more accurate. There are those who can hear to 20Khz and above but most people cannot.

Hearing Loss:
Hearing loss is cumulative. A single exposure to high sound pressure levels won't immediately cause hearing loss (unless, the sound level is extreme like a bomb or gun muzzle blast very near to your ears). As an example, you could work in an area where the sound pressure level is 90dB for years on end with no hearing protection, you could expect to suffer significant hearing loss. However, you could walk through that area a few times and suffer no loss.

Hearing loss starts with the higher frequencies. This may not seem important because vocal frequencies are near the low to mid part of the audio spectrum but it's the high frequency parts of speech that help you distinguish similar sounding words. When there is this type of loss, you have to repeatedly ask people to repeat what they've said. If you want to simulate this, pack loose cotton in your ears. This will attenuate (reduce) the higher frequencies. You'll see that it's a bit harder to understand what people are saying.

Level of Protection:
The reduction of the sound pressure level in decibels, without specifics, may not tell the whole story. Higher frequency sounds are more damaging than low frequency sounds. For example, you can easily withstand a low bass note of 140dB. Some may even consider that pleasant. If you were exposed to higher frequency sound, like that of a locomotive horn at 140dB, hearing loss would occur more quickly.

For the better quality hearing protection, you may see a level of reduction vs frequency. As an example, you may see that the attenuation is only 20dB at 125Hz but 40dB at 8kHz. You need to choose hearing protection that will reduce the level of all frequencies to a safe level. If you're going to begin working somewhere that requires hearing protection, contact the employer to see what they suggest (what other employees like) or what's required.

In some instances, you may have to use two protection devices to reduce the sound pressure to safe levels. This is generally done with foam ear plugs (no tether) worn with around-the-ear earmuffs.

Simple Foam Ear Plugs:
This type of ear protection is inserted into the ear canal. They are available without the tether. I find this type uncomfortable but they're popular, especially with people who work in hot environments (like those who cut grass) and need hearing protection for most of the day. These are the least expensive of the hearing protection on this page. Expect to pay about $2 for these. The bulk-packed, non-tethered type of foam ear plugs are commonly sold for about $10 for 50 pairs.

These are similar to the ones above but don't go as deeply into the ear canal. They are more commonly used by those who need to change from protected to un-protected repeatedly.

Around-the-Ear Muffs:
The previous types of hearing protection are not meant to be used by more than one person. If you need hearing protection that will be used by more than one person, you'll need something like the muffs below. These work well where it's not too hot but can get uncomfortable quickly if it's hot and you're sweating. Although this type can be shared, it's not ideal (what is considered 'adequate hygiene' varies greatly). If these are to be shared, there are hygienic covers that can be applied to the pads or wrapped around the ear cups. These will reduce the effectiveness of the ear muffs slightly so that needs to be taken into account when using them. Expect to pay $20-$40 for passive (no electronics) around-the-ear muffs.

Important:
The over-the-ear muffs require that the foam liner in the cups be intact. If the material has deteriorated or is missing, the muffs will not meet their specifications for level attenuation.

The ability to determine where a sound originates from requires that we have two independent inputs for sound (two ears). When sound is louder in one ear than the other, you can tell that the sound originated from the side of the ear that heard it at the higher level. When you use hearing protection, especially ear muffs, the ability to detect the location of the sound may be impaired.

Active Hearing Protection:
Active hearing protection like the type below uses two independent microphones to allow you to determine the direction from which the sound originated. This is important in areas where there may be danger (if you hear something crashing to the ground, you need to be able to tell where the sound is coming from). All of the previous types of hearing protection reduced the levels of all sounds, including sounds that you may need to hear for safety or in some instances, instructions from those around you (like those from a range officer at a shooting range).

The electronics in active hearing protection allows sound to be passed from external microphones to internal speakers. The internal amplifiers can actually amplify the perceived level and allow you to hear sounds that you wouldn't ordinarily be able to hear. The quality of active hearing protectors varies greatly, however. The first pair is a cheap pair and I cannot recommend them. They do what they are advertised to do but don't do it very well. The cheap pair amplifies sound but the frequency response is very limited. You can hear birds chirping and other higher frequency noises (upper vocal frequencies) but not much more. Although the second pair isn't audiophile quality, they do reproduce a much wider range of frequencies. The way these two operate is different as well. The cheap pair has two level controls. You have to turn on each side individually. There is no connection between the two ear cups.

On both pairs, there is a jack to allow you to connect an audio source (MP3 player, FM radio, 2-way radio, phone...). The cheap pair only passes audio to the internal speakers when the internal amplifiers are off (volume control/switch set to off). The ones below allow the audio to pass through when the internal amplifiers are active. When the internal amplifiers are switched off, the audio from the audio source is switched off. The audio source level is affected by the volume control (only one control for the muffs below) but the control isn't linear. The level is about the same for the external source from minimum volume to 1/2 volume. Above 1/2 volume, the external volume increases significantly and remains at essentially the same level up to the maximum volume for the volume control.

Notes:

  • To remove the battery cover, grab the ear cup with the black cover with both hands and use your thumbs to push the cover straight up and off of the cup. Use two thumbs on the side instead of one in the middle because , without batteries, there is a deep battery well and applying force in the center could cause the cover to be cracked.
     
  • Most headbands on headphones ear muffs are expanded by pulling addition length from the headband. That's not the case with these. The wires pull out from the plastic tubes on the cups.
     
  • The audio muffs above are Howard Leight Impact Sport muffs and are generally used by shooters. They are lower profile than the cheap ones on this page and allow you to get your head down lower to a rifle stock. Typically, electronic muffs like these allow the ambient sounds to be heard (sometimes to a level greater than the original sounds) but when a loud noise occurs (gun shot, etc), the audio level from the speakers is reduced for a fraction of a second to protect your hearing.

I've used these when cutting grass. They work well (although a bit warm) and allow you to hear the mower at a safe level (volume control set to about 60%). This is important because you want to be able to hear any sounds that may indicate that there's a problem. I used it with an MP3 player (Sanza Fuze+) and while it didn't play quite loudly enough, it was clearly audible (probably better for listining to a ball game than for music). The glasses didn't prevent the muffs from sealing properly.

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Perry Babin All rights reserved