Junichiroh Fujimoto

The audio spotlight: An application of nonlinear interaction of sound waves to a new type of loudspeaker design

This work was done to devise a new type of loudspeaker. The theory for sound reproduction of this loudspeaker is based on nonlinear acoustics of sound wave interaction in air. A finite amplitude ultrasound wave that can be amplitude modulated by any audio signal is radiated from a transducer array into air as the primary wave. As a result, an audio signal is produced in the air because of the self‐demodulation effect of the AM sound wave due to the nonlinearity of the air. It is possible to get a flat characteristic of reproduced sound pressure by using an equalizer. In some fundamental experiments the characteristic of the reproduced sound pressure is not quite flat due to an imperfect transducer array. Improvement of the transducer makes it possible to get a flat characteristic. A special feature of this loudspeaker is its very sharp directivity pattern, which makes it possible to realize a sound spotlight.

Methods for forming reference voice patterns, and methods for comparing voice patterns

A method for forming a reference voice pattern to be stored in a library for use in identifying an unknown input sound. The method comprises the steps of inputting a first sound pronounced for a particular letter combination by a speaker to form a first voice pattern, the first voice pattern represented by a sound energy level as a function of time; examining the first voice pattern to determine whether or not an intermediate voiceless interval is present within a predetermined time period at least from either a beginning or terminating end of the first voice pattern; repeating the inputting and examining steps for a second sound; combining the first and second voice patterns to define the reference voice pattern, wherein, if either of the first and second voice patterns has a voiced portion in the predetermined time period and the other of the first and second voice patterns does not have a corresponding voiced portion in the predetermined time period, the combining step comprises adding the voiced portion to said other of the first and second voice patterns.

Identification of voice pattern

A voice pattern identifying system includes a library for storing therein a plurality of registered voice patterns and a register array into which a sampled voice pattern is temporarily stored for comparison with said registered voice patterns one by one. The voice pattern is represented by a plurality of frames which are sampled at a predetermined time interval and each of which includes a predetermined number of data at different frequency ranges. The registered voice patterns are stored as compressed in the library so that each frame is accompanied by a compression data indicating how many times the corresponding frame should be repeated with time. In accordance with the present invention, there is provided a pattern compander which only modifies the compression data of either of the registered or sample voice pattern so as to make the number of frames identical before determination of the degree of similarity the two voice patterns.

Voice recognition system and method involving registered voice patterns formed from superposition of a plurality of other voice patterns

After sampling a voice signal by a microphone (31), a voice interval is detected by a voice interval detector (32). Then, the voice signal is processed by a frequency analyzer (33) having a predetermined number of channels at a predetermined time interval, whereby a corresponding portion of the voice signal is quantized at each channel. Then, quantized data obtained from these channels are binary converted (34) to thereby form a frame comprised of a series of binary data. Each data of this frame corresponds to one of the channels, and preferably it is set to be an integral multiple of a computer calculation unit (e.g., 4 bits, 8 bits, etc.). When forming a combination frame by superimposing two or more of such frames, the combination frame is divided into layers, whereby it is so structured that each bit is represented by a binary number in each layer. On the other hand, it may also be so structured that one frame is divided in a plurality of sub-frames and a preliminary comparison process is carried out using each sub-frame.

Determination of the vibrating phase by a time-averaged shadow moire method

By the general time-averaged shadow moire method only amplitude distribution of an object vibration is recorded. In this paper determination by means of the time-averaged shadow moire method of the vibrating phase of an arbitrary position on the object is presented. In this method the illumination angle of the reference grating is periodically oscillated at the same frequency as the object vibration. Therefore, stationary contour fringes are shifted to a vibrating region that vibrates in-phase oscillation of the illumination angle. Accordingly it is possible to determine the vibration phase of each region on the object as the signal phase added to the illumination angle oscillator.

Speaker-independent word recognition using fuzzy pattern matching

Abstract A new pattern matching algorithm, employing fuzzy logic for speech recognition, is proposed. In the field of speech recognition, there are two problems to overcome before realizing a speaker-independent speech recognition machine. They are firstly, fluctuation of pattern length, and secondly, that of frequency, caused by the variance of utterance speed, and differences of resonance frequency of the vocal tract, respectively. In the described algorithm these fluctuations are translated into membership functions. The membership functions are regarded as templates for pattern matching. In this paper, after the basic theory of recognition is described, the theory is modified to a form easily used by machine. As an experimental result a recognition rate of 93.2%, enrolling 120 words, was achieved in the case of Japanese. In the case of other languages 92.8% and 93.7% were achieved for English and German, respectively. These results indicate this method is realistically accurate. It seems to be worth noting that these results were achieved using a simple algorithm and accordingly the machine is small and inexpensive.

Vibration Analysis by Wavefront Modulated Holography

Wavefront modulated holography is proposed to measure the relative phase of each part of a vibrating object. The fact that there is no need for phase adjustment of the modulated reference beam is a remarkable merit. To realize the wavefront modulation, a seesaw mirror is used. In this method, the magnitude of the modulated phase of the reference beam is related to the position on the recorded plate. It is possible to measure the amplitude of the object vibration and the relative phase of each part of the object. To compare the calculated value with the measured value, this method is applied to the measurement of the vibration of two reeds whose relative phases are known. The measured value agrees with the predicted value. A small amplitude vibration less than λ/4 can also be detected by this method.