Drumhead Experiment

Andrew Kwong

Experiment No. 8

1. Title: Drumhead

2. Introduction:

In this experiment, we focus on the kinds of overtones that occur when a simple drumhead is struck. We will analyze the first few overtones in the sound and compare them with the other sounds and instruments we have analyzed in this class. From the reading, we know that drum heads create anharmonic overtones, meaning that the frequencies of the overtones are not integer multiples of the fundamental. Therefore, drums do not make a determinate pitch. The major difference between a one dimensional string and a two diminutional surface (such as a drumhead) is that in a one dimensional string, each particle passes all its energy to the next one, whereas each particle of the two dimensional surface only passes some of its energy to the next particle and passes it onto several others. Therefore the further from the source of the vibration you are, the lesser the amplitude is. Although the overtones of drums are not integer multiples of the fundamental, they are not too far off, which makes the ear perceive it as having an ‘almost definite’ pitch.

3. Setup/Parameters/Procedure:

First we download the drumhead file from Dr. Bach’s music link. Then we open the sound file in Raven using the physics of music presets. We drag the time selector line int he waveform graph to around 0.6 seconds and look at the overtones in the spectrogram slice. We look for any true harmonics and, measure and write down the first several overtones. To measure the overtones of the drumhead, we will go down to the selection table and add the peak frequency option. This shows us the peak frequency in any selection we make. To find the frequency of the overtone, we highlight enough of the overtone to encompass the peak of it and take down the number in the peak frequency column of the selection table.

We then analyze the overtones taken by calculating the ratio of the frequencies compared to the fundamental. Then we...