Ctr. for Comput. Res. in Music and Acoust., Dept. of Music, Stanford Univ., Stanford, CA 94305
Pulsed noise has been detected in the residual of steady flute tones after elimination of purely periodic components. LMS adaptive linear periodic prediction was used to trace the waveform through its slight period-to-period fluctuations. The predicted signal was removed from the original leaving a breathy sounding residual to examine. Noise pulses in musical oscillators result from period synchronous gating of the driving means. Bowed string instruments exhibit noise pulses arising from alternating stick-slip motion, where noise is introduced only when the string is slipping. Distinct pulses are also exhibited by the saxophone in which the reed modulates air friction. Flute noise is more continuous than in string or reed tones. Short time Fourier transformation of the residual signal reveals that pulses are present, but spectrally weighted toward higher frequencies. A physical model of the flute incorporating a corresponding noise synthesis method is presented. Results of the simulation are compared for pulse quality and effect on frequency jitter.