JPS60254992A - Acoustic device - Google Patents

Abstract

PURPOSE:To prevent noise from spreading to the neighborhood and to improve acoustic effect to an objective person by providing an acoustooptic transducer which reproduces an original audible tone by the nonlinearity of air on a railroad crossing or pedestrian crossing, and radiating the acoustic wave from the electroacoustic transducer to passersby. CONSTITUTION:Nonlinear parametric speakers 101-106 which have very narrow directivity are used as alarms of a railroad crossing and installed over a road 11. In this case, plural speakers may be fitted in parallel so as to generate an acoustic wave in the same direction and widen the service area. In general, an alarm installed on a railroad crossing is for giving a warning to persons and bicyclists walking or riding on the road ahead, and the conventional alarm has wide directivity, so an acoustic wave is radiated in every direction, causing a noise pollution to a neighboring residential area, specially, at night. On the other hand, when those nonlinear parametric speakers are used instead of the alarm, only persons and car drivers walking and driving on the road ahead are given a warming and no noise disturbs the neighborhood.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electroacoustic transducer, and more particularly to an acoustic device that effectively utilizes parametric speakers with sharp directional characteristics.

Conventional speakers generally have directional characteristics that are close to omnidirectional, so they are unable to concentrate sound waves only in a designated area in the space, creating a sound field everywhere in the space. There are drawbacks to doing so.

In contrast, the applicant first radiates into the air ultrasound waves that have been amplitude modulated (or single-sideband amplitude modulation or other special amplitude modulation) by a signal in the audio frequency band at a finite amplitude level. We proposed an acoustic radiator as a nonlinear parametric speaker (electroacoustic transducer) that reproduces the sound wave of the original audible signal (modulated wave) that is self-modulated by the nonlinear effect of the air in space.

FIG. 4 is a configuration diagram showing an example of the above-mentioned nonlinear parametric speaker previously proposed by the applicant, in which l is an ultrasonic transducer (ultrasonic vibrator), 2 is a power amplifier, and 3 is an amplitude modulator. , 4 is a carrier signal generator (a sound wave region), 5 is a signal source (audible sound), A is an ultrasonic beam, B
is an audible sound reproduction sound field (crosshatching part), and the nonlinear parametric speaker has a very narrow directivity characteristic, but a certain distance from the ultrasonic transducer 1 is required to generate audible sound. be.

±--1 The present invention was made in view of the above-mentioned circumstances, and
In particular, this invention was made with the aim of providing a novel acoustic device that was not possible with conventional speakers by focusing on the directional characteristics of the nonlinear parametric speaker.

11 The configuration of the present invention will be described below based on examples.

FIG. 1 is a diagram showing an example of the case where nonlinear parametric speakers such as those described in L are used as warning devices at railroad crossings. In the figure, 101 to 106 are nonlinear parametric speakers,
11 is a road, 12 is a railway, and parametric speaker 1
Are 01-1Oe installed above the road? . Note that in order to widen the service area (audible sound reproduction sound field), a plurality of speakers may be installed in parallel so as to generate sound waves in the same direction.

Warning devices installed at railroad crossings are intended to warn people or vehicles ahead of the road, but conventional warning devices have a wide directional characteristic, so they emit sound waves in all directions. They cause noise pollution to nearby residential areas, especially at night.

On the other hand, when a nonlinear parametric speaker is used instead of an alarm as in the present invention, the alarm is given only to people or cars on the road ahead, and no noise is caused to nearby areas.

FIG. 2 is a diagram showing an example of the case where the old nonlinear parametric speaker is used as a guide chime for blind people at a crosswalk. In the figure, 201 and 202 are nonlinear parametric speakers (chimes), 21 is a roadway, 22 is a sidewalk, 23
is a crosswalk, and as shown in the figure, nonlinear parametric speakers 20 . ．． 202 is arranged. In recent years, music has been played at crosswalks at road intersections to indicate green and yellow lights for blind people. can be guided correctly to the opposite side. In other words, when a blind person crosses a crosswalk, he may veer sideways from the zebra zone, but in that case he will be out of the sound field and will no longer be able to hear the music, and the blind person will correct his direction and return to the sound field again in the correct direction. can be maintained. In this case, it is preferable to arrange two parametric speakers facing each other as shown in the figure so that a sound field is formed along the crosswalk.

Figure 3 shows the above nonlinear parametric speaker with an 8mm diameter.
This is a diagram showing an example in which the apparatus is used for audio reproduction of a movie, a 16 mm movie, a 35 mm slide projector, etc. In the figure, 30 is a nonlinear parametric speaker, 31 is a projector, and 32 is a screen. When a moving image or still image is projected onto a screen using an 8mm movie projector, the sound is generally played back through a speaker, but in conventional devices, the image and sound source are separated.
It gives it an unnatural feel. On the other hand, according to this embodiment, the parametric speaker 30 is connected to the screen 32.
The audible sound beam is scattered by hitting the screen, and the reflected waves from the screen are heard, so the viewer can feel as if the sound from the screen is being played back. , you can get a sense of nature.

As is clear from the description of the present invention, it is possible to provide an effective acoustic device that cannot be achieved with conventional speakers.

[Brief explanation of the drawing]

1 to 3 are plan configuration diagrams for explaining examples of the present invention, respectively, and FIG. 4 is a configuration diagram showing an example of a nonlinear parametric speaker used for implementing the present invention. 10, ~io6.20. ．． 202.30...Nonlinear parametric speaker (electroacoustic transducer), 11...
Road, 12...Railway, 21...Roadway, 22...Sidewalk, 23...Crosswalk, 31...Projector, 3
2...Screen. Figure 1 Figure 2

Claims (2)

[Claims] (1) After modulating the ultrasonic frequency band carrier signal with the signal from the DI listening station frequency band signal source, it is amplified by a power amplifier and guided to the ultrasonic transducer, and the modulated wave is brought to a finite amplitude level. an electroacoustic transducer that converts the sound wave into a sound wave and radiates it into the air to reproduce the original audible sound by nonlinearity of the air, the electroacoustic transducer is located at a railroad crossing or a pedestrian crossing, and the electroacoustic transducer A sound device characterized in that it is installed so that sound waves from the device are radiated toward passersby. (2) After modulating the carrier signal in the ultrasonic frequency band with a signal from a signal source in the audio frequency band, it is amplified by a power amplifier and guided to an ultrasonic transducer, and the modulated wave is brought to a finite amplitude level. an electroacoustic transducer that converts the sound wave into a sound wave, radiates it into the air, and reproduces the original audible sound by nonlinearity of the air, and is arranged so that the electroacoustic transducer radiates the sound wave toward a projection screen. An audio device characterized in that the viewer is made to listen to reflected waves from the screen.