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When dogs wear hearing aids
A dog’s ear is a multitasking organ that differs from a human ear in many respects, however there are also some crucial points of similarity. This is why dogs with hearing loss can wear human hearing aids, such as those provided by Sonova brand Phonak.
When a dog sleeps, it’s sound asleep, happily ignoring any disturbance by man or beast – until its master opens a tin of food, in which case any dog worth its salt will be on the spot in a second, thanks to an ability to use its hearing selectively and filter out unimportant background noise. This is all possible because a dog’s sensory cells are not connected directly to the ear, but link via special nerve pathways to the cranial nerve responsible for hearing – and dogs can simply switch these on and off, like a light switch.
This is not to say that dogs have especially good hearing, at least as far as volume is concerned, but they do have one advantage over their masters: they can hear very low and very high pitches. “While humans can only consciously perceive sounds between about 60 and 2,000 hertz, a dog is able to hear up to 65,000 hertz,” says Stefan Launer, Sonova’s resident expert in audiological research and Senior Vice President Science & Technology. This is why there is not much point in shouting at your dog when it is disobedient; instead, a softer command in a higher tone of voice is more likely to achieve the desired result.
In addition, dogs have 17 ear muscles to help them locate sound, and they can move their ears independently of one another across a wide radius. They can thus point the auricle of the ear in a given direction to pick up the sound waves from a source as efficiently as possible. This location ability is of equal use to dog and owner – the animals can hear commands perfectly, even when their masters happen to be out of sight.
But what happens when a dog loses its hearing? With plenty of patience and training, you can train it to cope with everyday life – or you can fit it with a hearing aid. And there have indeed been dogs wearing hearing instruments for a few years now: the first time a hound was fitted with a hearing aid that had originally been designed for a human was in 1987, at Auburn University in Alabama – and Unitron, based in Port Huron, Michigan, was involved in the design. “It worked because the ears of dogs and humans are anatomically similar,” explains Launer. The hearing aid was coated in foam rubber that could expand to fit in the ear canal. As Launer points out, training a dog is often an expensive business, so solutions like this can be both necessary and appropriate.
Peter Scheifele has experience of fitting dogs with such devices; as a professor at the University of Cincinnati’s FETCH LAB™ (Facility for Education and Testing of Canine Hearing & Laboratory for Animal Bioacoustics), he specializes in researching and assisting dogs with hearing loss. “Since the Brainstem Auditory Evoked Response Test (BAER) was developed for animals, we have seen lots of dogs with complaints like age-related hearing loss and pathological sensitivity to noise.” As dogs have both a vertical and a horizontal ear canal, custom fittings are essential. One of the most recent dogs Scheifele has fitted with a hearing aid – a wireless device made by Phonak – was a border collie from Austin, Texas.
Nonetheless, only a small minority of dogs are suitable candidates for hearing aids, as the researcher explains: “People know why they have a foreign object in their ear. A dog doesn’t, and will often not tolerate the hearing aid.” In addition, hearing instruments only make sense if the dog has some residual hearing in at least one ear, as the hearing systems do no more than amplify sound. “Humans have the same problem, which is why they are often fitted with cochlear implants.” Scheifele goes on to explain that dogs with residual hearing may not even be aware that there is any deficiency: “Hearing loss is a slow process and doesn’t cause pain.”
Sonova’s audiological expert Stefan Launer sums up: “Adapting hearing aids manufactured for humans to fit dogs is an exciting side project in research. I’m always glad to hear about positive results.”
If dog owners have the patience, time and energy to get their animals used to the devices, there is a good chance that pooch will once again be able to make out the soft sound of a tin of food being opened – and, most importantly, be able to hear his master’s voice.