Effects of relative phases on pitch and timbre in the piano bass range

Piano bass tones raise questions related to the perception of multicomponen t, inharmonic tones. In this study, the influence of the relative phases am ong partials on pitch and timbre was investigated for synthesized bass tone s with piano-like inharmonicity. Three sets of bass tones (A0 = 27.5 Hz, 10 0 partials, flat spectral envelope) were generated; harmonic, low inharmoni c, and high inharmonic. For each set, five starting phase relations among p artials were applied; sine phases, alternate (sine/cosine) phases, random p hases, Schroeder phases, and negative Schroeder phases. The pitch and timbr e of the tones were influenced markedly by the starting phases. Listening t ests showed that listeners are able to discriminate between tones having di fferent starting phase relations, and also that the pitch could be changed by manipulating the relative phases (octave, fifth, major third). A piano-l ike inharmonicity gives a characteristic randomizing effect of the phase re lations over time in tones starting with nonrandom phase relations. A measu re of the regularity of the phase differences between adjacent partials is suggested for quantifying this randomization process. The observed phase ef fects might be of importance in synthesizing, recording, and reproducing pi ano music. (C) 2001 Acoustical Society of America.