JPS59186498A - Parametric array microphone - Google Patents

Abstract

PURPOSE:To make a transmitter large enough to obtain necessary acoustic power and to obtain an excellent signal-to-noise ratio by obtaining a maximum detection output when a signal arrives from a receiver side. CONSTITUTION:A signal wave f2 enters from the side of the receiver 4 and is reflected by the transmitter 3 to cause non-linear interference with an ultrasonic wave f1 from the transmitter, so that it is cought by the receiver 4. The receiver 4 is sufficiently reducible in size and the arrival signal is never masked as a result. A signal arriving from the transmitter side is unnecessary, so the transmitter is made larger enough to generate an ultrasonic wave having a necessary level; and the excellent signal-to-noise ratii is obtained and the minimum frequency of a signal to be detected depends upon the size of the transmitter, so the size should by large enough.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a directional microphone that utilizes a sound field grid effect.

FIG. 1 shows the configuration of a conventional C-lamet IJ-tuck directional sound receiving system.

The oscillator 1 generates a frequency j1 in the ultrasonic range. This is supplied to the wave transmitter 3 through the S wave amplifier 2, and is emitted in the direction of the wave receiver 4 as an ultrasonic wave. Here, when an audio signal of frequency J2 arrives from the directional force of the transmitter 3, if the output of the ultrasonic wave is sufficiently large, these two waves cause linear interference, resulting in 11.
In addition to j2, secondary waves of j1 and j2 are generated. Therefore, after amplifying these with the preamplifier 5, 1. A signal wave can be obtained by demodulating PM or m with the retrieval unit 6 using +1 as the carrier and f1 and j2 as the sideband.The smaller the angle θ at which the signal wave is incident on the axis of the shunted transducer, the greater the interference distance. increases, the detection output becomes large, and as the angle becomes thicker, the output becomes smaller, and theoretically becomes zero in the 180° direction. A directional microphone is thus obtained. However, as can be seen in FIG. 1, since signals arriving from the direction of the transducer are detected, the dimensions of the transducer must be sufficiently small. For example, if the distance between the transducer and receiver is 5Qcm, and you want to detect the incoming signal frequency up to 15KH2, it is necessary to keep the size of the transmitter to about 5cm in diameter.Currently, however, a transmitter of this size is sufficient. does not reach the sound pressure level that causes air nonlinear phenomena. -In other words, in the conventional configuration, the maximum output is obtained when the signal arrives from the transmitter side, which limits the size of the transmitter and deteriorates the signal-to-noise ratio. It was connected to

The present invention is designed to eliminate the above-mentioned drawbacks. In other words, means is provided so that the maximum detection output can be obtained when the signal arrives from the receiver side. FIG. 2 shows a main part of an embodiment of the present invention. The signal wave -J2 enters from the receiver 4 side, is reflected by the transmitter 3, causes nonlinear interference with the ultrasonic wave 1 from the transmitter, and is captured by the receiver 4. The receiver 4 can be of sufficiently small dimensions so that the incoming signal is not masked by it. On the other hand, since the signal coming from the transmitter side is an unnecessary signal, the transmitter can be made large enough to generate ultrasonic waves of the required level.

On the contrary, the size of the transmitter is required to be large because it determines the lowest frequency of the signal to be detected. Specifically, when considering reproduction up to 200H2, a minimum diameter of about 5Qcm is required. FIG. 3 shows another embodiment of the present invention in which the transmitter 3 is shaped into a curved R shape to increase the ultrasonic level at the receiver position and improve the sound collection efficiency of the incoming sound waves.

Since it is difficult to realize this curved wave transmitter with a single element, it may be used by arranging a plurality of elements in a curved shape.

As mentioned above, the present invention has a means for obtaining the maximum detection output when a signal arrives from the receiver side in the directional sound receiving system. The transmitter can be made large enough to accommodate the required hydroacoustic transmitter power, resulting in a directional microarray with good signal-to-noise ratio.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the configuration of a conventional example of a directional sound receiving system, and FIGS. 2 and 3 are according to the present invention. <Lame) +1
FIG. 3 is a principle diagram of the main parts of an embodiment of the directional sound reception method. 1 is an oscillator, 2 is an oscillator amplifier, 3 is a transmitter L4 is a receiver, 5 is a amplifier, and 6 is a demodulator.

Claims (1)

[Claims] In a directional sound receiving system that utilizes the parametric effect of a sound field, a method is provided that allows the maximum detection output to be obtained when the signal comes from the receiver side force. l]-Tsukuarei microphone.