We propose a new technique for rejection of narrow-band interference (NBI) based on multiple-symbol detection of coherent or differential phase-shift keying (DPSK). We first show that the direct use of multiple-symbol detection offers poor performance when NBI is dominant. Our proposed technique employs a special signaling or coding scheme which is shown to be robust against NBI. The evaluation of bit-error rate (BER) shows significant performance improvement in NBI vis-a-vis direct multiple-symbol detection. When viewed as a coding scheme, the proposed signaling scheme is significantly simpler for achieving the same coding gain than conventional error correction codes.

Correct and robust measurement of fundamental frequency F/sub 0/ is requested in the analysis of speech sound, speech enhancement systems and analysis synthesis telephony employing F/sub 0/. This article proposes a new method to estimate F/sub 0/ utilizing the autocorrelation function of the log spectrum. This method is named ACLOS (autocorrelation of log spectrum). In this method, the fundamental frequency is estimated from the peak of the autocorrelation function along the frequency axis of the spectral pattern. It means that F/sub 0/ is measured by enhancing the periodic feature of harmonics on the spectrum. Experimental results indicate that ACLOS gives more robust and reasonable pitch information than other methods give.

This paper studies the convergence properties of the gradient adaptive lattice (GAL) predictor for an input time series consisting of real-valued sinusoids in white noise. An analytic signal representation of the input signal provides more reduced prediction errors. Increasing the stepsize, a faster convergence is obtained without degradation on the performance. Simulation results show that a complex-valued GAL with the analytic signal is superior to the conventional GAL with regard to the power spectral estimation and the convergence rate.>

A speech Processing system named SPAC (Speech Processing system by use of AutoCorrelation function) can successfully compress or expand the speech spectrum and reduce the noise level superposed on speech signal. By employing these functions of SPAC, three types of low-bit-rate transmission system, which bit rate is 8 or 10 kbps, have been proposed. These are zero-crossing+SPAC, ADM+SPAC, and band-compression and -expansion by SPAC (compression ratio : 3). Evaluation by hearing tests is made on these sytems, zero-crossing and ADM. It is shown that ADM+SPAC with 8 kbps can transmit natural and acceptable speech.

A speech processing system named SPAC (SPlicing of AutoCorrelation function) is proposed in order to compress or expand the speech spectrum, to prolong or shorten the duration of utterance, and to reduce the noise level in speech signal. A period of short-time autocorrelation function is sampled and spliced after change of the time scale. Transformed speech is quite natural and free from distortion. Applications of SPAC are expected in many fields such as improvement of speech quality, narrow band transmission, communication aid for hard of hearing, information service for blind, unscrambling of helium speech, stenography and so on.