The link between the tonehole lattice cutoff frequency and clarinet sound radiation: a quantitative study

Abstract

Musical instruments are said to have a personality, which we notice in the sound that they produce. The oscillation mechanism inside woodwinds is commonly studied, but the transmission from internal waveforms to radiated sound is often overlooked, although it is musically essential. It is influenced by the geometry of their resonators which are acoustical waveguides with frequency dependent behavior due in part to the lattice of open toneholes. For this acoustically periodic medium, wave propagation theory predicts that waves are evanescent in low frequency and propagate into the lattice above the cutoff frequency. These phenomena are generally assumed to impact the external sound perceived by the instrumentalist and the audience, however, a quantitative link has never been demonstrated. Here we show that the lattice shapes the radiated sound by inducing a reinforced frequency band in the envelope of the spectrum near the cutoff of the lattice. This is a direct result of the size and spacing between toneholes, independent of the generating sound source and musician, which we show using external measurements and simulations in playing conditions. As with the clarinet, the amplitude of the even harmonics increases with frequency until they match odd harmonics at the reinforced spectrum region.