drumming at the speed of sound
What is sound?
Sound is simply a pressure wave that propagates through a substance - usually air. Whenever your brain tells you that it heard something, it is because a pressure wave hit your eardrum. More precisely, acoustic energy travels to the ear drum and is converted to mechanical energy, then to chemical energy in the cochlea, and finally an electrical signal is produced and sent to the auditory cortex where we perceive the sound.
Let's look a little deeper:
Pressure waves travel through all sorts of substances, not just air. It turns out that the speed of the wave propagation depends on the how the density of a substance varies with pressure. This property is called compressibility. The more compressible a substance is, the slower the pressure wave will travel through the substance. A good way to visualize this phenomenon is to imagine a bunch of little springs that are all connected together. If the springs are very loose, you would expect a disturbance to travel very slowly from one end to the other. If the spring is very tight, disturbances will travel much faster.
Here are some examples for the speed of sound through various substances:
Air -> 343 m/s
Water -> 1482 m/s
Steel -> 5,960 m/s
What does this have to do with drumming? It has everything to do with drumming! Playing drums (or any instrument for that matter) is about making sound. When you play a drum, you are causing the entire drum to resonate. The motion of the heads, drum shell, and sticks all create pressure waves in the surrounding air. These waves then propagate through the air so that your neighbors can bask in your snare drumming prowess.
Sound delay
Unfortunately for us, the speed of sound through air creates many problems. Try to play clean with your snare drumming buddy when he/she is standing 10m away from you. Here is what typically happens in this scenario:
Player A taps off an exercise. Player B begins to play with the sound of player A's drum. To player B, the exercise sounds clean. Player A thinks the exercise sounds like a bag of #$%. This is simply due to the sound delay. When player B plays the first note of the exercise, he/she is already 'behind' by the amount of time it took the sound to travel from player A's drum to player B's ear. 10 meters divided by the speed of sound gives a sound delay of 0.029 seconds. Now every single note that player B plays is behind by that amount. In addition, it takes player B's sound an extra 0.029 seconds to travel back to player A's ear. So, from player A's perspective, it sounds like player B is behind by 0.058 seconds. That might not sound like a lot, but let's look at the situation where the two players are playing sixteenth notes at 160bpm:
First we calculate the amount of time between beats at 160bpm.
(160 beats / min) * (1 min / 60s) = 2.66 beats per second
Next, we know that there are 4 sixteenth notes for every beat:
sixteenth notes = 4 notes / beat
(0.376s / beat) / (4 notes / beat) = 0.094 seconds per note.
Now let's think about how this sounds from player A's perspective. Player A is playing a note every 0.094 seconds. For every note he plays, player B is answering back with a note 0.058 seconds later, slightly later than halfway between player A's notes. To player A, this whole situation would sound like pure dirt.
Conclusion:
Since the speed of sound is not infinite, we will always have to deal with sound delay. This is one of the most challenging aspects of cleaning a drum corps or marching band show, particularly when dealing with formations separated by large distances. Often times you will hear field judges say they heard dirt but were 'out of position.' The sound delay is what they are talking about. If they are standing off to the side of a snareline, a perfectly clean lick might sound very dirty from their perspective. This is also why you should never judge a drumline's performance from the end zone!