Vibrissae

Welcome to Saturday's most whiskery blog. My word of the week is vibrissae , definition: the stiff, coarse hairs near the mouths of most mammals (and carnivorous birds!), from the Latin vibrio, to  vibrate.

As all cat people (and probably dog people and even carnivorous bird people) know, those whiskers are not just for show, enchantingly handsome though they look...

the cat's whiskers

Cats are by nature long-sighted creatures and have difficulty focussing accurately on anything less than a foot or thirty centimetres away. Their whiskers solve the up-close problem, among several others. Each muzzle whisker (and they have twelve, symmetrically arrayed, on each side of their furry face) is loaded with nerves and at its tip is a sensory organ known as a proprioceptor. Whiskers are also much more deeply embedded in the body than normal fur, as they are connected to the muscular and nervous system. This makes them incredibly sensitive to vibrations and changes in environment. They can act like radar, picking up external information and sending sensory messages to the brain about the cat's surroundings. By this means they enrich the data a cat receives about the world around it, not only by day, but also at night (a key element of its ability to 'see' in the dark).

Thus their whiskers allow them to sense items that are too close to be seen clearly, particulary useful when dealing with prey or when walking along shelves or windowsills loaded with breakable artefacts. Their span is also supposedly a cat's width, allowing kitty to sense whether it can fit into a space or not - and for this reason whiskers should never be trimmed or they lose effectiveness.Cat people can also discern the mood of their cats by the state of their whiskers. Rigid or retracted whiskers denote anxiety, whereas relaxed whiskers (as in the picture above) indicate contentment. And if they are pushed right forward that is a sign of curiosity or analysis.

Making a graceful and calculated leap of subject, when early radio technology was being developed at the outset of the 20th century, and we're talking primitive crystal radio sets here, the fine wires used as part of the mechanism to convert radio waves - vibrations in the air - into audible sound were called cat's whiskers because they looked somewhat similar and performed something of the same information-receiving function. Of course, they were not real cats' whiskers, any more than the catgut used to string tennis rackets came from cats!


early radio - low feline fidelity

Various pioneers in microwave technology, for instance Bose in India, Braun in Germany, by trial and error found that in a device like the one illustrated above in which a crystal (usually galena or iron pyrite) was brought into contact with a vibrating wire (typically copper to begin with, later steel), a semi-conducting junction was formed, a primitive diode with the ability to demodulate the alternating current of radio waves and rectify them into audio modulations that could be heard through earphones (not shown in the diagram).

These early radios worked surprisingly well, requiring little adjustment and no batteries They were cheap to produce and were used widely - though the principle of how they worked only came to be understood in the decades that followed. From the 1900s to the 1930s, these crystal radio sets with their cats' whiskers plucked vibrations from the air to the delight of thousands of early-adopter radio enthusiasts until they were superseded by mains or battery powered valve radios that could provide the amplification that crystal sets lacked.

All of which mulling over vibrissae and crystal sets filled the imaginarium with ideas of cats listening to radios and in all likelihood, if they were real cool kitties, dancing the jellicle night away in that elegant Edwardian decade at the start of the last century.

dancing the night away

Radio Nine Live
Nothing shabby about two Tabbies
gyrating in delight of the moon.

Glossy in joyous, silent pageant,
for so it seems to simple human ears,
these elegant, groomed felines are
dancing the night out on velvet paws
to the swingingest of  party tunes
pulsing invisible through the sky
much like a subtle breeze.

As one, with grace they whirl,
a flash of spat, a fleeting glimpse
of  ribboned, curling tail, and all
their silvery whiskers picking up
on what we cannot hear, the sound
of Nine Live's orchestrated wheeze
vibrating loud and clear.

Thanks for reading. Stay groomed and tuned, S ;-)

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Sound Waves

Sound waves, which are really vibrations in the air around us, are collected by the pinna on each side of our head and are funnelled into the ear canals. These sound waves make the eardrum vibrate. The eardrum is so sensitive to sound vibrations in the ear canal that it can detect even the faintest sound as well as replicating even the most complex of sound vibration patterns.

The eardrum vibrations caused by sound waves move the chain of tiny bones (the ossicles – malleus, incus and stapes) in the middle ear transferring the sound vibrations into the cochlea of the inner ear.

This happens because the last of the three bones in this chain, the stapes, sits in a membrane-covered window in the bony wall which separates the middle ear from the cochlea of the inner ear. As the stapes vibrates, it makes the fluids in the cochlea move in a wave-like manner, stimulating the microscopically small ‘hair cells’. Cells near the wide end of the snail-shaped cochlea detect higher-pitched sounds such as a child crying, those closer to the centre detect lower pitched sounds such as a large dog barking.

As the hair cells move up and down then microscopic projections on top of them bump against an overlying structure and bend which causes pore like channels to open up and chemicals rush into the cell creating an electrical signal.

The auditory nerve carries these signals through a complicated pathway in the brainstem before arriving at the hearing centres of the brain, the auditory cortex. This is where the streams of nerve impulses are converted into meaningful sound.

When I was a Medical Engineer one of the jobs was to check the accuracy of equipment around the hospital. We had test equipment to do this but as often as not I’d check on myself as well. So, one day back in around 2008 I was in the Audiology Department and casually put on the headphones in the sound proof room and went through the test. At first I thought the headphones were faulty but after checking again I realised that I had a small hearing loss at 8 kHz. It wasn’t a problem and it was only when this subject of vibration came up that I remembered the occasion and I’m only mentioning it now as an example of how the body can compensate for slight faults.

 As a matter of interest the human hearing range of a healthy individual is between 20 Hz and 20000Hz with the higher frequencies ( or number of vibrations per second ) gradually fading during a lifetime. Human speech covers the range of 200 – 8000Hz.

What the auditory system cannot filter or compensate for, of course, is what sort of vibration is going into the ear in the first place. Personally, as far as I’m concerned, popular music stopped not so very long after Good Vibrations.
And this really did have vibrations.

Puerto Rico, Gran Canaria

Listen
to the rhythm of drills
breaking brown rocks
and space from hill
for elegant cranes
to turn in a Sun
taking huge factors
of grey lotion
smoothed over shapes
that are baking all day
that look forward to night
when the still white faces
of the apartments opposite
are made over with make up
of light and shade
and the dance of the drills
is taken by a bass
from the clubs and bars
of the red, white and blue district
and creeps through my bedroom
the high notes saved for three a.m.
the air in my room tuned to
Puerto Rico, you’re a great audience.
In the morning
listen
to the rhythm of drills.

Terry Quinn
First published in Equinox 2005

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