Thursday, October 7, 2010

Sound - 4


First lessons...

I trust most of you know swimming.

To those who don't, water is a scary thing, while to those who do, whether they are good or indifferent swimmers, a session in the water is a larky time. When you take somebody to the water first, the thing to do is to explain what fun it can be once you learn how to float at least, and then 'teach the ropes' like how to float, then how to hold your breath, how to take those first flailings of the arms and the legs. Then slowly things fall into place and you are on your own. After that a more knowledgeable person can comment on your 'style' and give you tips to improve your style--all from 'terra firma' without getting his feet wet even. How? Because you know enough to do the basic thing well; it is now only a matter of 'polishing'--which any intelligent person could manage with the right kind of help/tips.

Audio experimentation too is a lot like swimming, I guess.

Quite a few of my younger friends who follow the blog were impatient with me for "not coming to the point" ASAP-- that is, as soon as possible. And in their dictionary that means 'immediately'! I resisted the temptation to succumb to such a 'short-cut' method, fearing the very real dangers inherent in such an approach. Let us, please, spend a little more time to perfect our technique before venturing deeper, so to speak.

Knowing why you do what you want to do is part of the learning/knowledge process. Also, finding out why what you have done is not giving you the exact results you wished for is another step in the right direction. Everybody doing something needs tools. And some of the tools are physical; these days a lot many tools are software based; and yet others are intellectual--what you carry within your head.

So believe me, you have got to learn how to stay afloat and swim and not commit suicide--before you can try new tricks. So, please, back to the shallow water.....


In water, as well as in audio, balance is everything. But please don’t confuse it with the 'Left-Right' balance control for stereo,

though that too IS another important 'balance' for us.

If you will go back to the previous post and review things you will see that we spoke of 'aural balance'.
We have over the years somehow misled ourselves into thinking that drums = bass, and shrill sounds meant treble. Right....and wrong! If you were lucky to 'thump' a drum 'live'--any drum--and kept your ears open, you would have come to certain new conclusions. An 'easier' drum to learn the difference is the humble native 'mridangam' with its complex tonality. No musician will let you 'thump' his favourite instrument, so better request him to play a couple of bassy 'thumps'.

Close your eyes and 'stretch' the sound in your mind-- at least try to. The strong bassy thump will be followed by a very complex tone structure that extends well above the usual 'bass range', you will admit. Ask him to play a few more bars and you will easily 'hear' that the mridangam has a complex sound and it extends much above the 'foundation' of the low notes. Try it with other popular drums, and even with a Western kick-drum. You will --unlike the 'thump-boom car-stereo crowd'-- hear for yourself that even the huge kick-drum produces NOT a single frequency bass note.

When you talk over a phone, often you find it easy to identify the person at the other end, though the connection and the phone may not exactly be 'hi-fi'. How does this happen? The human voice is a complex mix of tones and overtones, all 'locked' to the physical nature of your 'sound-box'--your vocal cords, your throat and nasal cavity etc. Scientists have established that you dont need a 'hi-fi' range of 20 Hz to 20,000 Hz to identify and recognize the person. Intelligibility needs an approximate range from say, 400 Hz to about 4,000 Hz, and that includes both male and female voices, virtually the entire set of voices you are likely to come across in this wide world!

In a similar manner, the 'mix' of the basic tone and the many overtones lets you identify that, yes, "this is a mridangam", and "this is a tabla-dekka combo" and "this is a snare drum", and undoubtedly, " this is a kick-drum". Drums do NOT produce single-note thumps. So for your system to have some fidelity, it will have to preserve and reproduce that complex sound pattern in its entirety.
Frequency Range Chart
The ratio in which the low and the higher tones mix in real life is the 'balance' that we aim to preserve. If, for example, you increase the proportion of the lower notes, immediately it becomes somewhat unlike the original, and a gross imbalance can 'kill' the sound signature. This is why we spent some time twiddling the 'level' control of your bass bin of the 2.1 speakers to approach a 'realistic' sound, a sound that compared well with the original ‘live’ sound.

This is important, and you have to practice getting the 'aural balance' right--IF you are serious about fidelity.

Yes, you are familiar with the term FR and you have used it often. A mini quiz for you. Pause right here and tell me clearly what it is; explain it to me as if I were a dumb/deaf ignoramus. I will let you take about three minutes.

Your three minutes is up. Now, did you do that nicely so that my 'ears were opened'?? I dont know...

A typical real-world 'flat' FR curve
Frequency response is important because of the thing that we mentioned earlier--'aural balance'.
If you look at the spec sheet of virtually any audio equipment, it would contain a figure for that, and nine out of ten, it would include that magical range 20 Hz to 20 kHz too! We will look at all those figures and split our hairs much later.

Basically FR tells you how UNIFORMLY an equipment reproduces sounds within that specified range of frequencies, from the lowest to the very highest. An amplifier, naturally, should amplify everything fed into it.

But it should strive to preserve the LOUDNESS RELATIONSHIP between the various frequencies/frequency bands produced by voices and instruments. In other words, it should NOT over- or under-emphasize any frequency or tone. This is what we term that most desirable of qualities in any audio equipment--a flat frequency response, or “more correctly”, a frequency-amplitude response.

It is commonly accepted that the range we need for hi-fi reproduction is from 20 Hz to 20,000 Hz, and such a standard was originally specified by the German Standards Institution or DIN. Of course there are other 'finer details' for specifying that, into which we need not go now. But we should always remember why it is important. Without a flat FR, the delicate and correct 'aural balance' of the low and the higher tones would be lost or wrongly presented, and sadly, the fidelity will be lost.

And just go back and remind yourself what 'fidelity' means. Our whole exercise is to 'improve' the level of fidelity that we can achieve, though it would be a virtually futile exercise to 'gun for' absolute fidelity--at least under our typical conditions.

Now with those ideas clearly in your mind, go back to your listening experiments and experience.

As always, keep your ears open, and your brain buzzing with activity!!

Listen, and you WILL hear!!!

more to follow

1 comment:

  1. This is too much for a beginner,I believe..Oops..what an article..can't take it at once.