Pets|May 5, 2011 10:58 pm

BowWOW! Facts, observations and musings about Our Best Friends

Listen up: Dealing with sound, hearing loss

By Tracie Korol

As the Blue Angels perform practice maneuvers low over my house, I notice that with each pass my visiting pack flattens to the ground, ears clamped tight to the head.  The noise is painful to my ears and I understand the abstract of giant, shrieking flying things overhead: it has to bewilder conceptually and physically hurt my dog friends’ ears. We’re going to play inside until it quiets down.

Hearing can be visualized as waves of energy traveling along molecules in the air, transformed into mechanical energy at the ear drum, then amplified by small bones and finally transformed into the electrical impulses in the auditory nerve — resulting in what the brain registers as hearing. Dogs have a much different range of hearing than ours, extending into a considerably higher frequency than we can hear.

Sound frequency, the number of sound wave cycles every second, is measured in Hertz (Hz). The higher the frequency, the more sound waves per second, the higher-pitched the sound. According to Monika Wegler’s book, “Dogs: How to Take Care of Them and Understand Them:” “Humans pick up an average of 20,000 acoustic vibrations per second (Hz), whereas a dog is able to perceive between 40,000 and 100,000 vibrations.” In short, dogs hear a lot better than we do.

All dog owners can report a similar story. At my house, even if my dogs were dead asleep, snoring, at the other side of the house, no matter how quiet I attempted to be, creeping in stocking feet to the kitchen, opening a cupboard door with exaggerated care, I could always expect a trio of happy faces at my knees by the time my hand reached out for whatever snack I had in mind. What this means is, if you need to yell at your dog in order for him to pay attention, your relationship needs work. He can hear you just fine even when you whisper. Good dog handlers rarely raise their voices above normal conversational tone.

However, dogs, like people, can lose hearing for a number of reasons: infections; trauma and loud noise; genetic susceptibility; neural damage, etc. The most common form of hearing loss is called “conductive” hearing loss and it is caused by blockage of the ear canal — from foreign bodies, infections, or an excessive build-up of ear wax (cerumen).

Exposure to loud noises can cause “sensory” hearing loss, and this loss becomes progressively worse as the exposure continues over time. Dogs that are subjected to constant loud music will gradually lose hearing, and the loss can be permanent.  Quick impact, high-level noise such as gunshots also causes profound hearing loss. The Mississippi State College of Veterinary Medicine conducted a study in 2002 finding of all the gun dogs tested (40), all had marked hearing loss. “A partially deaf dog is not as effective as a hunter,” said Dr. Andrew Mackin, holder of the college’s Hugh Ward Chair in Veterinary Medicine and an associate professor in small animal internal medicine. They recommended that hunting dogs wear earplugs, much as the hunter does.

There are many drugs that can cause hearing loss, too. Aminogycoside antibiotics such as gentamycin and amikacin; loop diuretics such as furosimide (Lasix); several anti-cancer drugs and even high doses of aspirin can damage hearing.  Be sure to ask for side effects or to read the package inserts before committing your dog to a course of medication. Diseases such as diabetes, kidney failure, and hypothyroidism may be associated with hearing loss, too.

As a dog ages, much like his human friends, his hearing diminishes.  The first sign may be a hesitancy to obey commands or a reluctance to go into strange territory.  Old age hearing loss is usually a slow, progressive change and you may be able to slow it down somewhat with good nutrition, antioxidants and adding some herbal supplements to the diet.

An old dog may initially lose only the ability to hear certain frequencies—usually the upper ranges. Speaking to him in dulcet tones may be helpful. I’ve advised clients to use percussive sounds such as clapping that can be heard by fairly deaf dogs. A clap can draw a dog’s attention to hand signals.  Realize, too, that hearing loss can create behavioral changes. You may notice something that looks like aggression. In reality, it may be your dog was unaware of your approach, became startled when touched, and instinctively reacted. Some old guys can be startled easily and may snap or bite when surprised.

The last form of hearing loss is “neural” hearing loss, the least common form. It can be caused by head trauma, blood clots, ruptured blood vessels, or brain tumors.

The good news is that hearing aids have been developed for dogs, but are pricey. Best to teach hand signals in basic puppy training and refresh the memory frequently, just in case.

 

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