Variation with Loudness of the Harmonic Structure of Clarinet and Bassoon Tones

Previous work [J. Acoust. Soc. Am. 33, 806 809 (1961)] indicated qualitatively that the number of higher harmonics in the clarinet tone decreases as the tone becomes softer. This matter has been investigated in more detail. The artificially blown clarinet described earlier was set up in the anechoic chamber at UCLA. The standing wave in the instrument was observed by means of a microphone in the mouthpiece; the sound radiated was observed by means of another microphone 3 ft distant at 90° from the axis of the instrument. Microphone outputs were analyzed on a Model LP-1a panoramic analyzer. The loudness of the clarinet tone was monitored by means of a General Radio sound-level meter. The harmonic structure of the clarinet tone for several different notes of the scale was recorded at four different loudness levels. It was found that the higher harmonics disappeared as the tone became softer, the number of harmonics decreasing from as many as 15 or more for loud tones to 1 or 2 for soft tones. The same experiments were performed with the bassoon with somewhat similar results, except that the soft tones may still have considerable harmonic content. (This work was supported by a grant from the National Science Foundation.)