While researching a recent tome I discovered much about the wonder that is mammalian hearing. As the so-called mammal-like reptiles of the Triassic shrank, from the size of large dogs to small dogs to cats to mice to shrews, they also changed in shape. The tooth-bearing bone of the lower jaw (the dentary) expanded, kettling the other bones at the back until they left the jaw completely and were swept into the middle-ear. There, the bones of the jaw joint, specifically the articular (in the back of the jaw) and the quadrate (the bone in the skull with which it articulated) became respectively the malleus and the incus, joining the time-hallowed stapes to give a chain of three tiny bones (the ossicles) connecting the eardrum to the inner ear. Mammals have a new jaw joint, in which the dentary articulates with another bone in the skull, the squamosal.
The result was transformative. The ossicles allowed hearing of refined sensitivity and at much higher pitches than reptiles could manage. Even birds — which still hear with the reptilian system, and its single stapes bone — cannot hear pitches higher than about 10 kilohertz (kHz), for all their trills and tweets and coos. Yet small children can hear up to 20 kHz, and this is positively cloth-eared compared with dogs (45 kHz), cats (85 kHz) and dolphins (160 kHz).
It was as if the first true mammals discovered a door in the high hedge surrounding the dark and dense woods in which they lived and found a wide-open vista the existence of which they had not suspected.
I use the word ‘small children’ above advisedly. As we humans age, we tend to lose our ability to detect the higher pitches (I am now 60). Over the past few years my own sensitivity to higher pitches has declined, such that I am now affectionately known chez Gee as ‘You Deaf Old Bugger’. After months of resistance I was finally persuaded to get my hearing tested, which I did at an audiology branch of a well-known chain of optician. My audiogram showed significant loss of sensitivity to higher-pitched sounds, especially above 2000 Hz (2 kHz). It is these frequencies that define consonants in everyday speech. This hearing loss explains why when Mrs Gee asks me to send reinforcements as the Russians are going to advance, I think she is asking me send three and fourpence, the Russians are going to a dance. The family has had to endure regular subtitling on TV – either that, or volumes too high for the rest of the family to tolerate.
Although I have abused my hearing throughout my life with exposure to loud music, mild to moderate age-related hearing loss is very common. There might also be a genetic element. Close relatives younger than I have hearing aids. So, in the past week I have joined the ranks of the hearing-aided.
What a revelation it has been.
I cannot pretend it is anything like the experience of the first mammals. However, we can turn down the volume on the TV and radio here at chez Gee and subtitles aren’t always a must. My hearing aids are also equipped with bluetooth which is brilliant. I can listen to music or audiobooks as I engage on my daily round — something I was used to doing with earbuds. And there is an app for that (of course) so I can control my hearing aids from my phone.
It was rather disconcerting initially. For the first two days or so the world did seem rather ‘fizzy’ as I could hear ‘noisy’ and high-pitched sounds well for the first time in years. I didn’t realise how much birdsong there is, even in midwinter. But I learn that it takes time for one to learn to live with the experience and after a few days it settles down.
There are downsides – if I want too play music through studio headphones I need to take my hearing aids out. And, as I am one of the few people with sufficient sense left in the world to wear an FFP2 mask in crowded public spaces (one wonders if the NHS would be quite so burdened with flu and COVID cases were mask wearing compulsory in public spaces), putting on and removing a mask is quite tricky when there are hearing aids in the way. But that’s an argument, perhaps, for another time.
