ASA 127th Meeting M.I.T. 1994 June 6-10

4pSAa1. Wave analysis and synthesis using almost-periodic functions.

Mikio Tohyama

Satoshi Ushiyama

Dept. of Inf. Eng., Kogakuin Univ., Tokyo, 163-91 Japan

Masahiro Izuka

Sound Craft Corp., Tokyo, 166 Japan

Yoshimutsu Hirata

Research Specialist, Tokyo, 192 Japan

Spectrum estimation is inevitable for wave analysis and synthesis. Frequency components of a signal are usually estimated by an FFT type of method based on harmonic analysis. This paper demonstrates synthesized waveforms and their spectra analyzed by the nonharmonic method that has been recently proposed by Y. Hirata (to be published in J. Sound Vib.). A conventional FFT-based method generally suffers from severe truncation effects on the spectrum analysis, and consequently a waveform cannot be continuously synthesized in a time region over the observation time interval used for FFT analysis because of virtually assumed periodicity. The nonharmonic method using almost-periodic functions, however, can be applied for the signal analysis and synthesis in a time period over the observation interval. This nonharmonic method is applied not only to stationary waveforms but also to transient signals like room impulse responses. The temporal changes of the frequency components can be visualized without artifacts due to time windowing truncation.