The Physics of Music

Does that sound wierd? Normally you hear about the Mathematics of music, but not Physics. Well, this weekend, I discovered how Physics is truly involved in music, or more specifically, in taking care of and playing my instrument.

I play the baritone (pictured above). If you don't know what that is, it's basically a small tuba (another name for it is "tenor tuba") with a beautiful, mellow sound. I love it :-). However, my valves have been sticking recently, so my dad and I tried to figure out why. This involved taking out the valve, examining the wear patterns, cleaning the tube as well as the valve, and finding out that the bottom of the valve was probably sticking to the spring. After discovering this and cleaning the sticking valves, we put them back in, a simple process which involves valve oil (also pictured above. My valve oil container has a very small opening for the drops of oil to come out of, even smaller than what the top lookes like in the picture. But this bottle alone demonstrates a very important fluid principle. As I squeeze the bottle, the pressure my fingers applied is transfered to the walls is transfered throughouth the fluid. The pressure then pushed the fluid out of the bottle in accordance with the fluid equation of continuity.

However, my valve oil bottle is not the only part of my playing that displays the fluid equation of continuity. My instrument does as well. As I blow into my instrument via the small tube coming off the large bell, the air moves through the different tubes of my instrument, all of which are different sizes. I blow air into the small area tube at a fast rate, and as it travels through the instrument, the diameter of the tube gets larger, until the air comes out of the very large bell at the top. The diameter of the mouthpiece tube is 0.016m, and the diameter of the largest part of the tube that the air probably still completely occupies is about .12m. Thus, by the fluid equation of continuity, which states that V1A1=V2A2, the equation would state that 0.01149(Vbell)=2.01e-4(Vmouthpiece), or that the velocity of the air coming out of the bell is only 1.75% that of the velocity at which it goes in. That sure explains why the air coming out of the bell is barely noticable. Well, now that I know what the increasing diameter of the tube does to the air, I wonder what it does for the sound? Oh well, got to wait a little longer to find that out.