JPH04215399A - Super-directional speaker - Google Patents

Abstract

PURPOSE:To generate a dense voice band and to make a speaker into compactness by arranging an ultrasonic transducer array on the recessed surface of a parabolic substrate, and emitting an audible sound wave from the aperture of a center part. CONSTITUTION:The ultrasonic transducer array 2 emitting an ultrasonic wave is arranged on the recessed surface of the parabolic substrate 1 whose center part is opened, and a reflecting plate 4 is provided at a position nearer to the origin of radius of curvature of the recessed surface. The audible sound wave with high directivity generated by the nonlinearity of the ultrasonic wave and the air is reflected on the reflecting plate 4, and is emitted by passing an ultrasonic filter 3 also used as a waterproofing material to cover a hole opened in the center of the parabolic substrate 1. By employing such constitution, a compact speaker which generates the dense voice band can be realized.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an ultrasonic parametric transducer array that creates a highly directional sound band.

[Prior Art] There are relatively many applications related to speakers having a parametric effect that utilizes the nonlinearity of air with respect to ultrasonic waves.

Although this type of speaker requires a large amount of electrical energy, its output as sound is small and has the drawback of being extremely inefficient compared to general speaker types. Also,
In order to increase the output of the secondary wave of audible sound waves generated by the parametric effect, it is necessary to increase the output of the primary wave of ultrasound waves, which inevitably results in the emission of ultrasonic waves that are harmful to the human body. For this reason, there are applications in which a filter material that absorbs ultrasonic waves is combined with a reflector that reflects audio waves.

Among them, patent application No. 59-245136 (name of invention: parametric speaker, applicant: Matsushita Electric Industrial Co., Ltd.)
To explain this as a conventional example, as shown in Fig. 4,
An ultrasonic transducer array 01 (
It is necessary to consider the positional relationship between the driving source (drive source/sound source) and the reflecting plate 011 having a parabolic surface.

That is, it was necessary to install the ultrasonic transducer array at a position away from the path of secondary waves (audible sounds) that are reflected from the reflective surface and reach the listener 9 via the acoustic filter 013.

[Problems to be Solved by the Invention] For this reason, when a reflector having a certain area and an ultrasonic transducer array are incorporated into the speaker box 012, a box with a large volume is required, which poses a major restriction in terms of use. Become.

In other words, the biggest challenge with this type of speaker was making it more compact.

Furthermore, in the conventional structure, the sound pressure of the reflected sound was uneven because the sound wave emitting surface of the ultrasonic transducer array was not equidistant from the reflecting surface (l1, l2 in FIG. 4).

[Means for solving the problem] In order to overcome the drawbacks of the conventional method described above and to be suitable for a wide range of applications, an ultrasonic transducer array (which emits ultrasonic waves) is installed on the concave surface of a parabolic substrate with an opening in the center. an array of piezoelectric vibrators arranged in a mesh pattern), an audible wave reflection plate having a filter for absorbing ultrasonic waves is arranged near the center point of the radius of curvature of the substrate, and the substrate The present invention provides a speaker box in which the aperture of the speaker box is closed with a filter that transmits only audible sound waves, and that part is the front surface of the structure, and the back surface of the reflector plate is the rear surface of the structure.

[Operation] An ultrasonic transducer array that emits ultrasonic waves (primary waves) is arranged on the concave surface of a parabolic substrate with a hole in the center, and the position opposite to this concave surface, that is, the origin of the radius of curvature of the concave surface By providing a reflecting plate at a position almost close to the primary wave, highly directional secondary waves (audible sound waves) generated by the nonlinearity of the primary wave and air are reflected on the reflecting plate,
It is released through a hole drilled in the center of the parabolic substrate.

[Example] Figure 1 shows the basic configuration of an ultrasonic parametric transducer array type superdirectional speaker according to the present invention. ) is a plurality of ultrasonic transducer arrays arranged on the inner surface of the parabolic substrate, (3) is an ultrasonic filter that also serves as waterproof, and (4) is a reflector that reflects audible sound waves on its surface. It has an ultrasonic filter (5) that absorbs. Further, arrow (a) indicates the direction of travel of the superdirectional audible sound wave.

FIG. 2 is a sectional view showing a configuration in which the basic components of the super-directional speaker according to the present invention shown in FIG. 1 are housed in a speaker box, taking practicality into account.

In the figure, (10) is a speaker box, and (11) is a back plate that holds a parabolic board and houses wiring for mutually shooting ultrasonic transducer arrays (ultrasonic elements). Note that the arrow (b) in the figure is the emission direction of the primary waves (ultrasonic waves) emitted from the ultrasonic transducer array.

Further, FIG. 3 is an electrical system diagram for driving the superdirectional speaker according to the present invention. In the figure (20) is a power-up, an acoustic signal generator such as a tape recorder (30).
) is output to the transducer array.

[Effects of the Invention] The structural effects of the present invention are (1) By configuring the ultrasonic transducer array on the concave surface of the parabolic substrate, the aggregation of primary waves (ultrasonic waves) is improved and reflected by the reflecting plate. The secondary audible sound waves are emitted from the opening in the center of the polar board while maintaining directivity within a narrow range (zone). Therefore, compared to a conventional structure in which an ultrasonic transducer array is configured in a planar manner, a denser sound band can be created.

(2) Ultrasonic waves, which are considered harmful to the human body, are absorbed not only by the filter inside the housing (speaker box) but also by the inner walls, and are rarely emitted outside the housing.

(3) By adopting a parabolic sound source structure that emits audible sound waves from an opening in the center, the speaker can be made more compact.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of the basic configuration of a superdirectional speaker according to an embodiment of the present invention, FIG. 2 is a sectional view of a speaker box according to the present invention, and FIG. 3 is an electrical system diagram of a speaker system according to the present invention. FIG. 4 is a sectional view showing a conventional ultrasonic parametric speaker. In Figures 1 to 3, 1 is a parabolic substrate, 2 is an ultrasonic transducer array, 3 is an ultrasonic filter, and 4 is a parabolic substrate.
5 is a reflection plate, 5 is an ultrasonic filter, 10 is a speaker box, 11 is a back plate, 20 is a power amplifier, and 30 is an acoustic signal generator. Applicant's agent Patent attorney Takehiko Suzue

Claims (2)

[Claims] Claim 1: A large number of ultrasonic transducer arrays are arranged on the concave surface of a parabolic substrate having an opening in the center in order to pass directional audible sound waves, and the center of the radius of curvature of the ultrasonic transducer array is A super-directional speaker characterized in that an audible sound wave reflecting plate having a filter for absorbing ultrasonic waves on its surface is disposed near the point. 2. The superdirectivity according to claim 1, characterized in that a filter material that transmits only audible sound waves is disposed in the opening for passing directional audible sound waves. speaker.