The ear as a diligent, unique antenna

February 18, 2018 01:47 am | Updated February 19, 2018 03:41 pm IST

Pierced early in life by the merciless jeweller and pulled at regular intervals by the teacher at school and parents at home, the external ear lobes, pinna, to use the technical term, remain neglected by everyone but the fashion designer. I being a doctor it aids my livelihood, faithfully transmitting the soft lubb-dup sound from the heart through the tubes of the stethoscope.

Harsh irregular sounds indicate the start of a cardiac problem, while the absence of any sound indicates it’s all over.

How it works

From the warning of the approaching predator in the dense jungle to the departure announcement of the next train at the railway station, detecting, profiling and identifying audio input is vital for human survival.

Sound waves entering the outer ear canal create a vibration in the tympanic membrane in the air-filled middle ear, and that in a series of orchestrated bone-mediated mechanical movements sets off waves of impulse in the fluid-filled inner ear. The sensitive auditory nerve-endings pick up the signals of fluid movement and send them to the brain, making us smile, laugh, cry or grimace in irritation. The pinna acts like a dish of a radio telescope, directing the sound to the ear canal for processing; but that’s just one part of its many functions. The ear is a series of C-shaped folds, the outer one called ‘helix’, the inner one ‘antihelix’, surrounding bumps and valleys, with complicated anatomical names such as ‘cymba’, ‘concha’, ‘tragus’, ‘anti-tragus’ and ‘lobule’. It is built on a unique skeleton of cartilage. The cartilage is strong enough to take the stress of all that pulling in the school for boys, and loads of jewellery for girls. At the same time, it is supple enough to take the weight of our ego-filled cranium every night, springing back to the original shape in the morning as you hook up your headphone, ready for the morning jog. Don’t forget, your designer sunglasses have to rest their feet on the ‘ear’. The complicated yet simple design of the ear makes sure the area of sound reception covers a near-360 degree span, reflecting most of the sound reliably to the ear canal. The design also ensures that soft sounds like a whisper are magnified by around 10 decibels, to preempt people conspiring against you. While loud sounds are carefully split and fragmented, part of the fragmented frequency is fed into the ear canal with a short delay, making them cancel part of the original waveform. This not only protects the delicate inner ear but helps localise the source of the sound.

Efforts to replicate the shape of the ear to improve the reception of dish antennae have proved futile.

Noisy India

In Indian society, sound rules, the louder the better. From crying children to blaring horns, political rally to music concert, from shouting vendors to haggling customers, the louder person seems to be the winner. The progressive increase in the incidence of hearing loss in society confirms the notion. With the slow disappearance of the traditional three-generation family in India, elders are losing their support and welfare; at the same time, modern medicine has ensured a steady increase in life expectancy. Progressive loss of hearing tends to push an otherwise healthy elder into a world of confusion, mockery, silence, withdrawal, even depression.

When my father turned 75 we could sense that his hearing loss was evolving into a social crisis, progressing from louder TV volume to inability to answer the door bell. Our suggestion of an ENT check-up and subsequently a hearing aid, were summarily rejected. We went for an appeal through a powerful advocate, his grandson, and bribed the judge, a granddaughter.

A simple but curt one- liner, “ Appuppa , now you can’t hear me when I call you from the hostel over the phone. I shall not call till you get a hearing aid,” settled the issue amicably. Now both grandfather and granddaughter have devices plugged into their ears, one to enhance hearing, the other to block parental advice.

With time, sound changes. Remember the first week after your marriage, the soft sensuous voice of your wife? Ten years later it must have toughened, for obvious reasons; in case it has not, take her to a specialist: there might be a problem with her voice box.

Time and sound wait for none. At least the clock hands move; the pinna just sit and watch.

tinynair@gmail.com

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