Grades 3–5 · Arts & Music
Why does a drumhead make a sound after one strike?
A drumhead is a stretched surface that can bend and spring back. A strike briefly changes its shape and transfers energy to it. The head keeps moving after the stick has left because it can store energy in its stretched shape and in its motion.
In the diagramA drumhead passes vibration to air and another headA strike supplies the starting energyTop head bendsAir couples headsBoth heads move surrounding airThe sound fades as vibration energy transfers out.Sound carries energy into surrounding air.
In a drum with two heads, the upper head also changes the pressure of the enclosed air. That air pushes on the lower head, so the heads and the shell interact. Their moving surfaces disturb the surrounding air. Those disturbances travel outward as sound, rather than carrying the whole drum through the room.
The vibration gradually becomes smaller as energy leaves through sound and other transfers, including heating. A hand resting on a head can make it fade faster by taking energy from the movement. Head tension, size and material also affect how the drum vibrates. One strike sets several patterns of movement going together, helping give a drum its particular sound. The sound continues while those movements last and fades as their energy passes elsewhere.
About this explanation
Starting knowledge: Understand back-and-forth motion and that energy can pass between objects.
Sources
- Yamaha — How Sound Is Produced: The Drum
- University of Southampton, Institute of Sound and Vibration Research — Membrane Modes