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

Tuesday, October 5, 2010

Sound - 3

Surely, that is NOT a plug for the Californian speaker company whose tagline is 'now hear this', and who 'wanted to save the world from bad sound', according to the founders.

That, per se, is a laudable and noble aim. You may not know, nor think it a great calamity, but the world is increasingly getting mired in 'bad sound'. One man's bad sound will be another's worse sound, if not the worst. As in quite a few situations, here too you need to have some 'standards', without which all such subjective statements become no more than highly prejudiced, if not ill-informed and downright stupid, 'rants'. Hence my earnest call, "now hear this..."


That is 'live' sound, and one has to admit, that is as natural as it comes! There are companies and companies in the audio field and of course, an almost wild range of products too. But when it comes to audio designs, it is a fact that often one that is designed by an engineer who is also a musician, sounds a bit--or sometimes a lot-- 'different'.

So let us hear this.....this difference.

I want you to be a little bit adventurous and 'experimental’. If you are a musician, or can get a musician friend to co-operate, all the better. Otherwise, do not worry, but you might look a bit silly to other folk at home while 'experimenting'. I assume that most of you own and use computers and these days the computer can double up as a pretty good sound system, a better recorder than the typical cassette machine of yesteryears, and even as a combination test equipment like say, an audio signal generator or an oscilloscope. The possibilities are there and they are within reach of the average hobbyist or enthusiast. Now get hold of a good microphone--not the cheap one that comes with the standard ‘chat’ headphone. Buy a good compatible separate microphone that plugs into your sound card. The plug will be like your headphone plug, but one connection supplies an operating voltage to the microphone. So buy one that is compatible.

Fire up the sound recorder or some other software you use for recording and try recodring with the mic so that you are familiar with  the drill. Now in an average room with some peace and quiet, ask your musician friend to play his instrument. A flute can sound wonderful in almost any setting, and so can a saxophone. We are likely to have violin playing friends, and some 'mridangam' (that is a South Indian drum for accompaniment in classical concerts, dance programmes etc) artists too.

Let them sit away from the walls, as far as possible, and play for a while, so that you have the sound of the instrument etched into your mind, in a way. Towards the end of this 'live' session you can put your finger into one ear, and move around closer to the instrument to discover from where and at which distance it sounds clearest. Now ask him to play for another few minutes and put your mic in the earlier-discovered position and hit 'Record'. Save the file after giving it a suitable name.

If you can play and sing, or at least read a play aloud with some nuances, it will be even better. Save that file too. Next (especially for those without musical abilities!) take a few things like a toy drum, or even a plate and spoon and try banging it like you have gone nuts a little. The aim is to listen to the sound of the banging and remember how it all 'sounds'. Record a few sessions like that. Your imagination and your resourcefulness set the only limits here! (It will be an interesting exercise to record yourself also, singing or reading aloud--so that later you could 'discover' yourself.)  In all the above situations make sure that as the mic is a single 'mono' mic, it is placed as close as is possible to the source so that it is immersed in the ‘direct sound’ and is not flooded by strong reflections and echoes.

Your first attempt at playback of the recorded files will be a strong lesson in disappointment. Your recording of the flute or mridangam or violin will sound like a 'dead and artificial' ( I picked the words as being the opposites of 'live' and 'natural'; but it pretty much illustrates the result) instrument. But then listen some more and see if there is something you like in that recording. When you listen a lot and do some mental comparisons, you will come to realize certain things. Your recordings--all of them-- sound as if they are 'covered by a veil'. This 'veil' is the loss of fidelity brought in by the imperfections primarily of the cheap mic, the reverberant small room etc. But overall, the digital recording process of the computer software preserves without much loss most of the things that have been fed into the system.
'Live' music at a temple
It is also advised that you should attempt to go to venues where somebody is singing and playing live. Not 'live' rock shows or other such 'modern' shows where high-powered amplification is the rule rather than the exception. But to places where one or two people sit around with their instruments and 'jam'. If you visit a village, especially a north-Indian village, opportunities galore for experiencing 'live' musical evenings. I feel this aspect of listening to 'live sound' under various settings, becoming familiar with a range of voices of all sorts and shades and colours, is important for the aspiring hi-fi enthusiast. One wonderful thing it does is to set you free from “notions of bass and treble” and such other often dubious and confusing terminology, and lets you learn to assimilate what could be termed the 'aural balance' of a natural setting.

Flautist par excellence--Lord Krishna
Now the 'trap' has been baited with tasty morsels. You have heard your friend play and sing in your own room, and, honestly, it has been an 'ear-opening' experience. At first it sounds like it is nothing great, but on a second or third 'listen' somehow you 'grow close' to the sound. For me the sound of the flute as it 'filtered through' the fingers of my young friend and neighbour wove a mystical curtain of sound. Not ‘impressive’ in a big way, but very subdued and soft, and it was vibrant with 'life'.

When I played back my sound file from the computer hard disk, it didnt at all sound like my friend did just a few minutes back. I could/would never in my life accept that as a 'stand-in' for the 'real thing', I vowed. Most of you too will go through that experience when you try it. But then tell yourself, just because a well-known friend has put on a 'veil' does it mean that you cant recognize him/her? No way. Some of the features might be veiled, but it is the 'genuine' person all right. This is something like it.

Forget about stereo and mono and all that. I assume most of you have your "2.1 speakers" plugged into your computer. That is the usual left and right channels for stereo and a 'point one' channel for the lower octaves or the bassy sounds. We will examine the theory behind such systems and their desirability etc later. Now put those two 'satellites' (such 2.1 systems are also called 'sub-woofer/satellite’ systems, or sub-sat for short. Again, terms like 'sub-woofer' need to be examined in detail--later.) on both sides of your computer monitor, and preferably away from walls and corners. Place the 'sub' on a shelf where it is easy for you to adjust its 'level' control.
Popular 'sub-sat' speaker systems
Forget that you know the meaning of 'bass' and start the playback of your file. Rotate the sub's level control all the way to zero and listen. If it is a flute or violin or bulbul, you wont miss MUCH. Well, if your recording is that of a drum like the mridangam or a heavy male voice, you will perceive that the reproduction is somewhat 'thin'. It lacks the 'foundation' of the lower notes. Now SLOWLY advance the level control so that you think you could sense the recording slowly getting "nearer to the original sound" you had heard in your room--let the 'veil' be there for the time being. Stop right there. Now play back some of those other files, including the banging sessions. Spending an hour or so in such an exercise will leave you with a totally different notion about the 'balance' of what you hear. Now sit back and listen, move yourself forward and back, adjust the volume control for a comfortable level that 'approaches' the level of sound your friend produced playing live. Continue to listen and listen...and listen.

LISTEN... and you will HEAR !

Very slowly you will love hearing your recording. You will soon be hearing many nuances that you never even suspected were there in the recording! And the sessions will have a guaranteed effect-- it will leave you 'aching' for the 'real thing'...your friend and his flute, time and again.

Those who have a good pair of stereo microphones and a preamp for plugging them in, may try feeding the signal to the computer and recording it again. Dont aim to achieve 'stereo' or anything like that. Just place the mics about a couple of feet apart so they catch the 'direct sound' and not the reflections that swamp the room. If you have an old cassette recorder, you can put it into record and pause, and feed its output via a cable to the computer and record that. This newer recording will sound far better than your earlier one. Again, play with the reproduction levels and try to achieve a sound as close to the live sound as possible. The live sound as you heard it in your room is the 'touchstone' upon which you judge the reproduction.

You will be surprised how close you can get to the 'real sound' though the 'veil' will be there. Truly it will be, as I said earlier, an 'ear-opening' experience, and we need that if we are to 'judge' what is ‘good’ and what is not.

How many times have you noticed cars driving by with a strange 'thump' emanating from them? Those are the 'subs'. Even ‘respectable’ speaker makers market them with the tagline (yes, I recently saw that in an ad) “get punched by our subs”, with accompanying picture of a ‘sub’ driver unit and a boxing glove!

Have you ever asked the important question, are those subs contributing only 'their percentage' of the total sound, or are they brashly 'dominating' the 'balance'. No question, they ARE.

Last question: Then will that be music? If you are crazy to put a nut inside your car with a drum set and let him bang away to his heart's content and then try to reproduce similar levels with your subs and the rest of the equipment, you might be able to claim that it IS music. But that is the time for you to ask yourself  again: Does that system make it easy to identify the sound of different drums? Or do they all sound the same with an overwhelming, thumping 'bass line'? Honest answers are not very pleasant. So too is truth!

The reproduction of music is dangerous territory with all sorts of difficulties lurking round the corner to trap you if you are not careful. But it is not often your ears will lie to you.

Listen to them, and dont hurt them with loud thumps that masquerade as music. If music was just thumps,  man wouldn’t have invented all those other instruments! And, come to think of it, man's ingenuity has given us a vast range of drums! And if you listen closely and carefully they will speak their language to you.

The art lies in listening!

So remember, keep your ears open, and your brain switched on!

more to follow