Use of optical signal processing techniques to spectrum analysis of speech

A new optical processing system for spectrum analysis of speech was proposed. The main components of this system is an optical processor and a micro-computer. The processor consists of a He-Ne laser, optical lenses, and photographic film plates. Since the optical signal processing is inherently parallel for two-dimensional signals, time-varying spectra of one-dimensional signal of speech can be obtained without shifting a window along the time axis. Based on the results of a computer simulation for the spectrum analysis of speech, the optical processor was designed and constructed. Various /V/, /VV/ and /CV/ utterances were analyzed by using the optical processing system. The close agreement between the frequency spectra obtained by the system and those obtained by the simulation confirms that the system operates as expected. Non-linear time warping, indispensable for spoken word recognition, was shown to be accomplished by controlling the transmittance function of the windowing plate.