Thursday, August 14, 2008

Science of Sound

Thanks for all your responses for the posts on Carnatic music. As much as it might be interesting and new to you, it is the same here. And hence, I would like to reiterate that I am not an expert in this domain. I am merely trying to learn with you all and this series of posts will help us to get there, I hope.

Some of you mentioned that there are 12 notes instead of 7 and some said even 16 and so on. True. I was about to discuss this in my next post and your responses prompted me to do little deep dive into this topic.

In order to understand how many notes are there in the system, we need to understand the science behind the sound.

Human ears have the capacity to sense variations in air pressure as long as the frequency is in between 15/20 Hz to 20,000 Hz. Any sound below this 15/20 Hz is called infrasonic and any sound above this 20,000 Hz is called ultrasonic. While species like bats, dogs etc. can sense ultrasonic range; snakes, whales etc. can sense infrasonic waves. This could possibly explain why many species sensed TSunami and the loss of such species were minimal compared to human!

Anyways, coming back to 7 swaras, this range of 20 - 20,000 Hz is broken into 10 segments. (See below)

S1 S2 S3 S4 S5 S6 S7 S8 S9 S10

So, S1 is closer to 20 Hz whereas S10 is closer to 20,000 Hz. Now, each segment is divided into 7 sub-segment leading to 7 swaras in each octave. Guys, trust me. I sweated to give you this picture in Excel.

Due to the limitation of time & resource, please note that the frequencies against each note is not ACCURATE, however, it is very close.

The point to note here is that the middle A (in C4 segment - highlighted in yellow) has a frequency of 440 Hz. This is like our J2EE specification. Any manufacturer globally has to comply with this requirement. So, Middle A is like a reference point. If you know Middle A's frequency, you can multiply by 2 to get the equivalent frequency of A in the upper octave. And continue divide by 2 to get lower octave's frequency.

Each instrument has its own frequency range. Please see to know more details about the instruments and the frequency range.

Anyways, back to our topic. How many notes are there - Theoretically INFINITE. Yes, if and only if our ears are capable of distinguishing such minute levels of frequency changes. Unfortunately, dwelling in this noisy world, we cannot distinguish minor variations. Hence, the notes are divided into 7 in each octaves. However, notes like Ri, Ga, Ma, Da, Ni have a variation. Like how we have even Tylenol coming in Vannila and Strawberry flavor, Ri has two variations - Ri1 and Ri2. Let me give a crude example (though not accurate). You can consider frequency of R1 = (Sa + R2)/2. In other words, R1 is a semi-tone. Similarly, we have variations for Ga, Ma, Da and Ni.

If you are ever wondering what are those BLACK keys in keyboard, they are these variation keys of the above said swaras.

Rest in next.


முருகேஷ் said...

It's getting very interesting. I must appreciate your efforts.

I use to wonder why there is no Ti, Da, Gi like sounds included in swaras. From this post I understand they also can be part of swaras but for practical purposes it is limited to original 7. Am I correct?

Emjay said...

Right. Though there can be infinite notes in an octave to cover the range, it has been scientifically proven that human ear can distinguish between only 22 notes in an octave. However, for all practical purposes you have only 12 swaras, 16 - if you take into account of Vivadhi swaras. (I intend to cover Vivadhi swaras in my subsequent posts)