How Much Loud Noise Can a Dog Tolerate?

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Is your environment too noisy for your dog? It is generally agreed that dogs have better hearing than human beings, especially in the higher frequency ranges. It is also a proven fact that exposure to loud noises can be damaging to hearing.

Many published guidelines describe safe exposure levels to loud noise for humans. However, no such guidelines existed for dogs—until now. A new set of recommendations for noise exposure in dogs has just been put out by a team headed by S. L. Mak of the School of Science and Technology at Hong Kong Metropolitan University.

Sounds Can Cause Hearing Loss

Ears are designed to register sounds and send that information to the brain. However, there is a dynamic working range for all ears; sounds that are too low in intensity are simply not processed, while sounds that are too loud may actually cause damage to the auditory system. The damage to the ear comes about due to simple mechanics. The inner ear begins to process sounds when the auditory vibrations at the eardrum are passed on and ultimately create movements of fluid in the inner ear (the cochlea).

The movement of this fluid, in turn, causes tiny hair-like filaments to flex, thus sending a neural signal up to the brain. Sounds that are too intense cause too much bending and flexing of the hair cells, and they break much like a wire coat hanger might break if you vigorously bend it back and forth many times. Broken auditory hair cell filaments do not regenerate. That means that for each set of broken hairs, the ear's ability to register the sounds which these hair cells normally respond to is lost.

Research has shown that exposure to loud sounds is the primary environmental cause of hearing loss. A lot of data about humans demonstrates that loss of hearing due to noise exposure is a major, widespread problem. The U.S. Centers for Disease Control and Prevention (CDC) estimates that in the United States, 12.5 percent of children and adolescents aged 6-19 years (approximately 5.2 million) and 17 percent of adults aged 20-69 years (approximately 26 million) have suffered some degree of permanent damage to their hearing from excessive exposure to noise.

Which Sound Levels Are Safe and Which Are Not?

Decibels are the measurement units used for the intensity of sound. Humans can hear decibel levels starting from 0 dB (the minimum threshold of hearing) up to 120-140 dB (the sound threshold of pain–roughly equivalent to an industrial chainsaw, jackhammer, or the sound of a jet aircraft taking off). Sounds at these higher levels can be very dangerous to human hearing, and even short exposures to such loud sounds can cause measurable hearing losses.

The U.S. Environmental Protection Agency (EPA) has concluded that exposure to an average of 70 dB or less is a sound level that will not cause measurable hearing loss over a lifetime. A normal conversation is at about that level, as are typical office or restaurant noises, and the sound of a dishwasher or vacuum cleaner also falls in that range.

It is generally accepted that sounds over 85 dB, depending upon the period you are exposed to, can damage your hearing. Examples of noises that produce sound levels above 85 dB include a garbage disposal unit, a diesel truck, a motorcycle, a leaf blower, a snowmobile, sports crowds, and rock concerts.

The likelihood of damage to the ear depends not only upon the sound's intensity but also its duration. Safe listening time is roughly cut in half for every 3 dB rise in noise levels over 85 dB. For example, you can listen to sounds of 85 dB for up to 8 hours before damage begins to appear. However, if the sound goes up to 88 dB, it is only safe to listen to the same sounds for four hours. If the sound level rises to 110 dB, the safe listening time plummets to one minute, while exposure to 120 dB or above may cause virtually instantaneous damage to the ear.

Do Dogs Respond Similarly to Loud Noises?

If we look at a dog's ear, we find that it is structurally very similar to that of a human. The similarities include the fact that the final translation of sound vibrations into the neural signals that are sent to the brain depends upon the same type of hair cells as those found in humans. This suggests that dogs might also be susceptible to lose of hearing due to exposure to loud sounds.

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Early research tended to focus on hearing losses in dogs as being mostly due to age or as being due to genetic factors. Therefore, when data emerged showing that certain types of dogs, like retrievers and pointers, were more likely to show hearing losses, this was chalked up to breed specific genetics. However doubts began to arise when later data began to suggest that it is only the dogs which were actually used in hunting which showed these losses in hearing.

The dogs who actively worked with hunters clearly shared the same genetics with the identical breed of dog that was not used for field work. Measurements of sound levels from hunting rifles and shotguns show that the sound of firearms can exceed 140 dB in intensity (which is in the range where sound can be instantaneously damaging).

Furthermore, sporting dogs, such as pointers, are usually out in front of the hunter's gun where the sound level is highest. So perhaps the loss of hearing in sporting dogs was due to their exposure to these high-level sounds. This supposition seems to have been recently experimentally confirmed by a team of Turkish researchers at Mehmet Akif Ersoy University, who demonstrated that loss of hearing can appear in working pointers due to trauma from exposure to the high levels of noise made by firearms.

Recommended Safe Sound Levels for Dogs

Based on a survey of the available data, this latest report from Hong Kong suggests that the level of noise which is acceptable as being safe for human beings may actually be too intense for dogs with their more sensitive hearing. For human beings the acceptable ambient sound level averaged through the day should be around 70 dB or less. But dogs have more sensitive hearing than people, and they can hear sounds, especially high-frequency sounds, which are inaudible to humans.

These researchers concluded that the average environmental sound level for dogs should be at least 20 dB less than what is recommended for humans. That would be around the sound levels that one would find in urban residential areas, namely 45 dB to 55 dB.

They concluded by saying "As humans, we know the hazards of loud noise to ears, and therefore it is our responsibility to take care of the dogs by creating an environment that is noise-free and conducive for them to live."

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