6.6 The Influence of Wall Material on Brass Instrument Performance
315
Fig. 6.24 (a) Experimental setup for studying the effect of wall vibrations on a trumpet played
by an artificial mouth. (b) Power in each harmonic of the played note B 2 with the bell damped,
divided by the corresponding power with the bell free. From Moore et al. (2005)
Fig. 6.25 Experimental apparatus for measuring the effect of damping wall vibrations on a french
horn sounded by an artificial mouth. Courtesy Wilfried Kausel
Similar results were obtained in measurements on a french horn carried out at
the Institute of Musical Acoustics in Vienna (Kausel et al. 2010). This experiment
was performed in a large anechoic chamber (Fig. 6.25a), and the artificially blown
horn was encased by a wooden box which could be filled by sand to damp the wall
vibrations (Fig. 6.25b). A dependence of the relative sound powers of harmonics
on damping over a wide frequency band was again observed, with the powers of
the lowest harmonics augmented by damping and the powers of higher harmonics
diminished. This small but measurable influence of wall damping on the spectrum
of the radiated sound was also found when the artificial lips were replaced by an
acoustic driver.
315
Fig. 6.24 (a) Experimental setup for studying the effect of wall vibrations on a trumpet played
by an artificial mouth. (b) Power in each harmonic of the played note B 2 with the bell damped,
divided by the corresponding power with the bell free. From Moore et al. (2005)
Fig. 6.25 Experimental apparatus for measuring the effect of damping wall vibrations on a french
horn sounded by an artificial mouth. Courtesy Wilfried Kausel
Similar results were obtained in measurements on a french horn carried out at
the Institute of Musical Acoustics in Vienna (Kausel et al. 2010). This experiment
was performed in a large anechoic chamber (Fig. 6.25a), and the artificially blown
horn was encased by a wooden box which could be filled by sand to damp the wall
vibrations (Fig. 6.25b). A dependence of the relative sound powers of harmonics
on damping over a wide frequency band was again observed, with the powers of
the lowest harmonics augmented by damping and the powers of higher harmonics
diminished. This small but measurable influence of wall damping on the spectrum
of the radiated sound was also found when the artificial lips were replaced by an
acoustic driver.