Acoustics Theory for Drum Tuning: Equalising the Drumhead
The first overtone frequency of the drum, which we call 'F1' is excited most when the drumhead is hit at the edge and sounds like a PING.
The F1 overtone frequency is important to ensure that the drum is tuned evenly and vibrates with a clean and consistent profile. If one point has a slightly different frequency, this causes a vibration clash on the drumhead which makes the sound of the drum warble or modulate. In acoustics we call this condition ‘beating’ which occurs when two or more close but not exact frequencies occur at the same time. Beating in the drumhead means that the sound is not smooth and you don’t get the pure tone of your drums when they are hit.
Unfortunately, because of the many different frequencies being excited on the drum at the same time, it can often be really hard to hear of different points are the same or not. It can even be hard to hear if one is higher or lower than another, because our ears get drawn to different frequencies and our bran finds it hard to interpret all the information. We call this the limits of ‘psychoacoustic perception’, but generally it means there are only so many frequencies our brain can hear accurately at only one moment in. Tim - so don’t feel inadequate if you find this aspect of tuning difficult!
The great thing about the iDrumTune app for tuning around the lugs at the edge of the drum, is that it’s programmed to ignore all of the other frequencies except the one that is most powerful, so it gives a reading and lets you know exactly which lugs are lower or higher than the first one you hit. You can then make some fine adjustments and measure again. If you get each point to within 1 Hz then that is really pretty good, and not many humans can hear to an accuracy of 1 Hz anyway, apart from a few incredible individuals who have perfect pitch and can tune a piano with no assistance.
Apple (iOS 10.3 upwards): http://bit.ly/iDrumTunePro
Android (V8 upwards): http://bit.ly/iDrumTuneAndroid
http://www.idrumtune.com