There’s Life Above 20 Kilohertz! A Survey of Musical Instrument Spectra to 102.4 KHz by James Boyk – California Institute of Technology.
Abstract
At least one member of each instrument family (strings, woodwinds, brass and percussion) produces energy to 40 kHz or above, and the spectra of some instruments reach this work’s measurement limit of 102.4 kHz. Harmonics of muted trumpet extend to 80 kHz; violin and oboe, to above 40 kHz; and a cymbal crash was still strong at 100 kHz. In these particular examples, the proportion of energy above 20 kHz is, for the muted trumpet, 2 percent; violin, 0.04 percent; oboe, 0.01 percent; and cymbals, 40 percent. Instruments surveyed are trumpet with Harmon (“wah-wah”) and straight mutes; French horn muted, unmuted and bell up; violin sul ponticello and double-stopped; oboe; claves; triangle; a drum rimshot; crash cymbals; piano; jangling keys; and sibilant speech. A discussion of the significance of these results describes others’ work on perception of air- and bone-conducted ultrasound; and points out that even if ultrasound be taken as having no effect on perception of live sound, yet its presence may still pose a problem to the audio equipment designer and recording engineer.
Each musical instrument family — strings, winds, brass and percussion — has at least one member which produces energy to 40 kHz or above. Some of the spectra reach this work’s measurement limit of 102.4 kHz.
Harmonics of French horn can extend to above 90 kHz; trumpet, to above 80; violin and oboe, to above 40; and a cymbal crash shows no sign of running out of energy at 100 kHz. Also shown in this paper are samples from sibilant speech, claves, a drum rimshot, triangle, jangling keys, and piano.
The proportion of energy above 20 kilohertz is low for most instruments; but for one trumpet sample it is 2%; for another, 0.5%; for claves, 3.8%; for a speech sibilant, 1.7%; and for the cymbal crash, 40%. The cymbal’s energy shows no sign of stopping at the measurement limit, so its percentage may be much higher.
The spectra in this paper were found by recording each instrument’s sound into a spectrum analyzer, then “prospecting” moment by moment through the recordings. Two instruments (clarinet and vibraphone) showed no ultrasonics, and so are absent here. Other instruments’ sounds extended high up though at low energy. A few combined ultrasonic extension with power.
The mere existence of this energy is the point of this paper, and most of the discussion just explains why I think that the spectra are correct, within the limits described below. At the end, however, I cite others’ work on perception of air- and bone-conducted ultrasound, and offer a few remarks on the possible relevance of our spectra to human perception and music recording.
Complete article: here