Wind instrument very-nearfield and room-average spectra

Abstract

Woodwind and brass instruments radiate their lower-frequency components isotropically. At higher frequencies (above the tone-hole or bell-propagation cut-off frequency) each component is radiated in its own highly directional pattern which complicates measurement of overall spectral envelopes, even in a reverberant room. A microphone placed at the first open hole of a woodwind receives a rapidly convergent series of contributions from the lower holes. It is shown that both above and below the tone-hole cut-off frequency (≃ 1500 Hz for clarinet or oboe) the spectrum recorded by this microphone is very nearly the same as that obtained by spectral averaging of sounds recorded at many points in the room. Similar results are obtained for spectra obtained with a microphone placed one bell radius in front of a brass instrument bell. Despite the spectral match, the perceived tore color of nearfield recordings differ from those based on simple room averages, and from ordinary room listening. The auditory mechanism appears to be sensitive to early-echo spectral subtleties associated with the differing angular distribution of low and high frequency components. Implications for psychoacoustics, for recorded conventional music, and for electronically generated music will be discussed.