A friend of mine recently told me how she suffers from hyperacusis. People with hyperacusis have difficulty tolerating sounds which do not seem loud to others. For example, my friend can’t stand the sound of someone whistling a tune, or crunching a potato chip. She loves to be in silence, and avoids loud environments. However, there is one particular sound she finds very pleasing, and it’s a very ancient one: the Himalayan singing bowl.
Himalayan bowls are handmade using a bronze alloy that can include copper, tin, zinc, iron, silver, gold and nickel. They are played by striking the side like a bell, or by continuously rubbing the side to elicit the “singing” tone. When struck, the rich and complex overtones of the Himalayan singing bowl ring out.
I recorded the struck sound of my large, 13″ diameter Himalayan bowl. Using Adobe Audition software, I generated a spectrogram of the sound and isolated the fundamental note (F) and the ten strongest overtones. In the video below, each overtone is highlighted in the spectrogram as it plays. Time is represented on the horizontal axis, pitch on the vertical axis, and loudness corresponds to the brightness/warmth of the pixels.
In addition to unique frequencies, the overtones have unique rhythmic qualities. Each tone has a kind of tremolo, a regular wavering of volume (that “wahwahwahwah” sound). The tempo of this wavering is different for each overtone.
With a root note of F, the other strongest pitches within the sound are approximately C, E-flat, G, and A-flat. The sonority is basically the F minor ninth chord (1, ♭3, 5, ♭7, 9), although it doesn’t quite fit with the equal temperament of instruments like pianos and guitars.
I can’t say exactly why so many of us (including my friend who is so sensitive to her aural environment) enjoy the sound of Himalayan singing bowls, but the specific collection of overtones and their unique pulsations must have something to do with it.