Bridgestone Tire Company Limited

Sadao Nomoto

Kazuyoshi Iida

Yoshikazu Kondo

Keiichiro Mizuno

Masayasu Matsumoto

Noriaki Murayama

Kei Watanabe

Tomonori Katayama

Kenichi Onda

Keiichiro Tabata

Method and apparatus for forming a photographic record representing acoustic characteristics of a sound field such as the distribution of sound pressure and the distribution of equiphase surface wave are disclosed. A microphone and a light emitting diode are reciprocally moved to scan a plane in the sound field and an envelope signal of an output signal from the microphone is derived. The envelope signal is then sampled at a given sampling frequency to produce a sample signal. A carrier having a given frequency is amplitude-modulated with the sample signal to derive a modulated signal. Then, a switching circuit is controlled by the modulated signal in such a manner that when the envelope signal exceeds a predetermined value, the switching circuit is made on and off repeatedly and thus the light emitting diode is turned on and off at a rate of the carrier frequency to form a locas of the light spot. An image of the locus of the light spot is recorded optically on a photographic film.

Method and apparatus for forming photographic record of sound field

A device for controlling a propagation direction of noise, which is preferably associated with a sound insulating wall to significantly improve its sound reducing effect of alleviating noise emitted from a noise source such as a railroad, highway and the like on which an electric car and automobiles run. The device comprises a hollow structural body composed of a plurality of elongated vertical hollow passages arranged at right angles to a substrate and spaced apart from each other by means of partition walls. The upper noise inlet side surface of the hollow passages face a propagation direction of noise emitted from the noise source and serve to refract and lag in phase the noise passed therethrough, thereby producing a sound reducing region located intermediate between a direct sound propagation and the refracted sound propagation. In one embodiment, a pair of hollow structural bodies are arranged in opposition to each other to form an arch type device. In another embodiment, the hollow structural body may be provided at its noise inlet or outlet side surface with an extension of the hollow passages.

Device for controlling a propagation direction of noise

A noise control device which produces behind it an enlarged sound reducing region is disclosed. The device comprises a hollow structural body composed of a plurality of elongate hollow passages which are different in length and constructed such that the passage length is made the longest at a substantially center part in a vertical direction and is made gradually shorter from the center part toward upper and lower edges of the hollow structural body. The upper and lower edges allow direct propagation sound emitted from a noise source to pass thereover and therethrough.

Noise control devices

A device for controlling a propagation direction of noise which is preferably associated with a sound insulating wall to significantly improve its sound reducing effect of alleviating noise emitted from a noise source such as a railroad, highway and the like on which an electric car and automobiles run. The device comprises a hollow structural body composed of a plurality of elongate hollow passages superimposed one upon the other and spaced apart from each other. The passages are arranged in a propagation direction of noise emitted from the noise source and serve to refract and lag in phase the noise passed therethrough, thereby producing a sound reducing region located intermediate between a direct propagation sound and the refraction propagation sound.

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Kawasaki, Japan

Sadao Nomoto