Mikio Tohyama

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This paper investigates the significance of the magnitude or the phase in the short term Fourier spectrum for speech intelligibility as a function of the time-window length. For a wide range of window lengths (1/16-2048 ms), two hybrid signals were obtained by a cross-wise combination of the magnitude and phase spectra of speech and white noise. Speech(More)
This article describes a method of intelligible speech representation that uses narrow-band envelopes and their carriers. This method enables modification of the talker's voice pitch and speech-rate without sacrificing intelligibility. The carrier, which shows the instantaneous phase, conveys pitch information, while the temporal envelope conveys(More)
This paper presents an approach to distinguishing the zeros representing a sound source from those representing the transfer function on the basis of Lyon's residue-sign model. In machinery noise diagnostics, the source signature must be separated from observation records under reverberant path conditions. In numerical examples and an experimental(More)
Inverse filtering recovers the original speech by removing all the effect of the transfer function on speech perception in a reverberation sound field. However early reflections within around 30 (ms) after the direct sound increase the perceptional sound energy of speech sound. This article investigates preferable frequency characteristics for the early(More)
This paper describes the effect of two types of temporal permutations of the speech waveform on speech intelligibility. Using an overlap-add procedure with triangular-shaped windows for frame lengths of 1/8 to 2048 ms, the temporal order of the speech samples within each frame was subjected to either of two types of permutations: time-reversal or(More)
Reverberation morphing from an impulse response is an inevitable 3D-audio technology as well as reverberation rendering for an immersive communication network. This paper proposes a method for reverberation morphing by relocating the poles and zeros of the transfer function. It assumes that the distance of the pole/zero locations from the unit circle in the(More)
This study investigates a signal theoretic approach to rendering acoustic events. Acoustic events modeling language (AEML) is an essential part of acoustic events rendering using an acoustic-data stream based on structured audio representation. This article mainly describes sinusoidal and envelope-modulation modeling for intelligible speech modification and(More)
Sound power output from a source can be decreased in a closed space by using secondary sources. The minimum power response (MPR) from sound sources (both primary and secondary sources) is analyzed based on modal theory. The power reduction is observed experimentally for a pure tone source in a large reverberation room. The corner method for sensor location(More)