FIDELITY FUNDAS
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Used, over-used, misused, hyped....?
All those are terms that could describe a couple of very popular words.
Hi-Fi and Stereo.
How many of us 'connect' to the fact that hi-fi is short for 'high fidelity'? It is interesting to note the dictionary meaning and also look at what that 'high' is doing there. Any good dictionary will tell us that 'fidelity' means the 'faithfulness' or the ‘exactness’ with which the original is reproduced, copied etc. If the reproduction has 'fidelity', then it resembles the original. The greater the fidelity, the closer the resemblance. (We will return a bit later to these popular, but vaguely understood terms, including ‘stereo’. For the moment let us just say that 'stereo' --short for stereophony-- is only one of the many ways and means to achieve that elusive 'fidelity' in reproduction.) But first let us try opening our ears a little bit.
For our purposes, we could re-state fidelity like this perhaps. We expect that, say, a recording of Lataji singing at last year's Onam fest (?? !! ) at the Tagore Hall should, when played back, project a convincing 'make-believe' sound image as we listen to it in our living room. Had you been there at last year's 'live' event, you would have some ready 'reference' for judging the reproduction and its fidelity. If not, you would be happy if the reproduction could re-create in your room at least some of the 'ambience' of the original venue, and would evoke in you more or less similar emotions as you would have experienced there. But then you do not expect your small room to be transformed into the huge Tagore Hall; still you expect the recording to preserve and reproduce some of the 'live' ambience of the original performance, including its emotional impact. Really a tall order!
An interesting conundrum suggested by pundits with a sense of humour is the vexing question: What are you aiming for in your reproduction?
Do YOU want to be THERE ?
Or, is it that you want THEM to be HERE.
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| A concert in progress inside the Royal Albert Hall, London |
Or, do you want the reproduction equipment to 'transport' India's sweet Nightingale and her troupe and all the rest HERE to your smallish room, with its very ordinary acoustics: the ticking of the clock, the faint sounds of traffic in the road outside, the sound of water running in the adjacent bathroom, and the sound of the TV from the other room intruding into your reverie.
You might say, I would rather be 'there' in the concert hall. But it is not easy. What you are having right now as your sound system plays is a weak attempt at bringing 'them' 'here' into your room. Are you sure? Or do you find that at times you suspect you are 'there'? This philosophical conundrum probably will never have a true resolution at least with existing technology. Why?
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HEARING IS BELIEVING
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To answer that we have to look at the basics of our hearing mechanism.
We all say 'hearing is believing'; really, is it so? Ah, then how do you hear? If you think you hear with your two ears, let me tell you, you may be right, but you are more likely to be wrong there! Truly, we 'hear' with what is in between those ears--our complex brain. The ear-brain combo has developed in a particular manner over the millennia when man has evolved from a creature dodging the predators in the primeval jungles, to being a predator himself in the concrete jungles of the modern metropolis. Scientists are only now beginning to understand how we hear with the ear-brain combo.
There are powerful hearing-related mechanisms at work in our brains that have to be understood at a basic, simplified level if we are to understand the limitations of the reproduction chain in our homes--our stereo music systems.
Imagine our great, great, great.....great-grandfather in the vast plains of the ancient jungles. It is open ground with tall grass and trees and far away hills. Small sounds carry far, and what assail his ears is a mix of wind noise and the rustle of grass and leaves, sounds of a gurgling stream, punctuated by bird and animal sounds of all sorts. If you take a sound meter and measure the cacophony, it will be very loud most of the times. But suddenly there is the distinct sound of crunching gravel and the man is alert, his eyes focussing instinctively towards from where the sound came, probably from a large dangerous animal. This particular sound may not have registered at all on the sound meter, mind you, being so faint in comparison to the sum-total of all the other sounds! Then how did this miracle of hearing take place?
As he stood there in the open plain, the lack of echoes and other auditory clues told the man about the vast open nature of his environment. Though the background sounds were 'loud' to the sound meter, his brain told him to ignore it as they were just that--a background 'curtain of sound'. But when something totally new, faint though it was, intruded, the two ears immediately fed some information to the brain that did an 'on-the-fly' processing and gave the man the precise 3-dimensional point from where the threat came, and in an instant, he was ready, his fingers pulling taut the bowstring.
When in the evening he moved to a more 'closed' environment like his cave, with its 'intimate acoustics', populated by his chattering wife and kids and maybe a dog or two, the situation was slightly different. There were many echoes or rather, reflections, from the cave walls etc. This gave him an 'instinctive' appraisal of its size and other qualities, while at the same time his brain processed the sounds in such a way that this 'thick soup' of original sounds and reflections did not confuse him at all. He could follow his wife as she walked back and forth doing the chores while talking to him, the older children playing (there was no home work in those days!) and the dogs taking it easy. But a faint whimper from the baby would alert him, and if his 'better half' did not respond suitably, he would shout at her, probably waking the baby fully and making it bawl loudly, adding to the confusing 'acoustics'! ( Feminists need not worry too much about this 'homely' scenario. In the early 'hunting' days, it was the male who did that risky business. The female was content to let the male bring home the bacon! How the modern urban changes have altered everything, except perhaps the acoustics of the average home! Oops, I forgot the 'yakking' TV, that icon of modern 'civilization'...)
You can experience the confusing 'thick soup of reflections' by trying the following experiment. With your finger close one ear and listen with the other while being in an open space. Then slowly walk into the living room. You won't be able to bear the cacophonous assault of reflections on your ears! This is a good demo of how much of what the two ears 'hear' are selectively filtered out and even ignored by the brain in the interests of intelligibility and accurate 3-dimensional hearing. You might also have noticed that listening with one ear took away the ‘life’ of the sound image. Another related curiosity is the mechanism of the outer ear, or what the doctors call the pinna, which we pierce to put on all kinds of studs and decorations! Scientists have found that filling the contours of the outer ears slowly takes away the ability of the person to discern correctly sounds and directions. The more adventurous among you might even care to repeat that experiment!
If you are keen to develop your ‘belief’ in your ear-brain combo, you must try the following experiment too. Remember, today we live in a world of 'visual overload' and so we often ignore the capabilities of our ears. After dark, go to a room, preferably one that you do not frequent all that often and pause at the door. Close your eyes, 'open your ears' and then slowly open the door. Just stand there and maybe shuffle your feet, and listen....and listen. You may not hear anything at first, but then slowly you discover that you have a pretty good idea of the size of the room! You take a step and you feel that you can sense how far away the opposite wall is. Blind people can hear the reflections clearly as they walk, immersed in the cacophony of our mad streets, and we see them easily dodging obstacles. The faculty is in all of us, only that it has 'rusted' with disuse. You can try this a few times and discover how adept you become at 'judging' strange rooms and halls without the help of visual clues. It is all very complex, though our brain handles it all adroitly and without our being aware of it.
So, that tells you one important thing: your recording and reproduction chain has to preserve most of these clues if they want to 'cheat' your ears into telling you that you are in the Albert Hall --when you are really in your small living room, or maybe taking a morning walk wearing your headphones.
Can we have at least passable 'fidelity' in our homes? What can we do to 'improve' our experience of a recorded audio event?
We will look at some of these interesting aspects in the coming posts.
Till then remember to keep your ears open, and your brain switched on!
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more to follow
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