Physics of Music

The purpose of this experiment is to demonstrate the difference that ear should pick up, between hitting the note and missing it.

We will be using a wonderful web page called JavaTuner. Click here and it will open in a new window.

For this experiment, we will play Sa and Ga and try to tune them.

Please do the following setup on JavaTuner –

1. Click on the button Sound = “Repeat” (below the circle of notes)

2. Click on the botton Pitch = “A=440”

3. Click on C in the circle of notes. This will be our Sa.

4. Click on E in the circle of notes while holding down the shift key. This will be our Ga.

When you do this, both Sa (C) and Ga (E) should start playing simultaneously.

Listen carefully to the sound. What do you hear? Apart from the notes C and E, you also hear kind of fast oscillation like sound.

These oscillations are called “beats” per the acoustic physics terminology. The beats are created due to interference between the waves of dissimilar frequencies. The rate of beats is equal to the difference between the two interfering waves. For example, if one tanpura is tuned to a note of frequency 440 Hz (cycles per second) and other at 436 Hz, then you will hear 4 beats per second.

Tuning is all about eliminating these beats. So let’s do it. Using your computer’s down arrow key, start bringing down the frequency of the note E. As you start hitting the arrow key several times, you will notice that the oscillations start reducing. The eventually completely disappear when the frequency offset for E (shown in the Frequency table) is -14. If you further reduce the frequency, the beats reappear.

What is so special about -14? Read here about it.

You can repeat this experiment yourself for Sa->Pa (C->G), Sa->Ma (C->F), Sa->Dha (C->A) etc. The offset where the beats disappear will be different for each of these, but see if you can figure it out yourself.

Ability to listen to these beats and pick them up is extremely important. When people refer to someone having the “musical” ear, they probably refer to the ability of that person to pick up these differences. As the frequency of beats reduces, you are closer to hitting the note, but also it is more difficult to pick up the beats.

While there may be some in-born ability involved in having the “musical ear”, I strongly believe that one can train oneself to develop musical ear.

How does this theory apply to the bansuri? In the same way. If you have a tanpura playing in the background and you play Sa on the bansuri, you should be able to hear the beats (or hopefully, lack of them) to figure out if you are playing in tune. It is much easier to pick up the beats when two similar instruments are playing (two tanpuras or two bansuris). It is a bit more difficult to pick up beats when you are comparing note on tanpura with the note on bansuri (this is because acoustic characteristics or specifically frequency spectrum footprint generated by the two is a bit different). However, the basic principle remains the same.

Here is [amazon_link id=”0393334201″ target=”_blank” ]an interesting book that explains this theory in detail[/amazon_link].

This link leads you to a very interesting discussion on the physics of sound waves and its application to music.

http://www.physicsclassroom.com/Class/sound/soundtoc.html

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