3aAA4. Directional radiation by wind instruments.

Session: Wednesday Morning, May 15

Time: 9:10

Author: P. L. Hoekje
Location: Dept. of Phys., Univ. of N. Iowa, Cedar Falls, IA 50614-0150


As with most musical instruments, the radiation patterns of wind instruments include directional components that can provide the listener with important timbral cues in a room. The most significant radiation comes from vibrations of the internal air column that are transmitted either through the woodwind tone holes or the opening of the brass instrument bell. For each of these, a cutoff frequency can be defined that marks the boundary between low frequencies that are radiated isotropically and the very directional high frequencies. Thus the listener in a room with reflecting surfaces is presented with several ``views'' of the instrument, and each view has a different spectral distribution. The vibration of the walls of the brass instrument provides another but much smaller directional component. The amplitude of this signal is of the order of 40 dB smaller than the signal radiated directly from the vibrating air column, and so it will usually be masked. However, the longer decay time of this signal increases the chance of its detection. The radiation patterns of this signal are also much different, as well, being quadrupole or higher in order. [Supported by the Iowa Science Foundation.]

from ASA 131st Meeting, Indianapolis, May 1996