JP2574454B2 - Speaker device with directivity - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a loudspeaker device having directivity such that sound waves from a loudspeaker can obtain a strong sound pressure only in a specific direction.

[Conventional technology]

Conventionally, an acoustic lens has been used as a means for changing the directivity of a speaker.
Figure 13 shows.

A loudspeaker device using such an acoustic lens is used to eliminate the drawback that sound waves radiated from a finite-diameter loudspeaker have a sharp directivity as the frequency increases and strong sound pressure concentrates on the front. In many cases, it is equivalent to a concave lens of an optical lens, and converts a plane wave into a spherical wave.

The acoustic lens of the speaker device of FIG. 13 also attempts to equivalently change the wavefront by partially lengthening the path of the sound wave for this purpose.

This acoustic lens corresponds to a concave lens of an optical lens, and is formed by laminating perforated thin plates.

In this case, if the wavefront at the lens entrance is flat like a horn-type speaker, sound waves near the center axis are hardly affected by the lens, while sound waves around the lens bypass the lens stack. While passing, it is in a slightly delayed state.

As a result, the wavefront bends and becomes close to a spherical wave, so that a wide directivity can be obtained.

[Problems to be solved by the invention]

However, on the other hand, a narrow-directional speaker device that transmits sound only in a specific narrow range and does not transmit sound as much as possible to the other surroundings has been desired, but special devices such as parametric speakers using ultrasonic waves have been desired. Other than the perfect speaker,
Sufficient narrow directivity performance has not been obtained.

If the speaker device shown in FIG. 8 has a completely opposite configuration, it is possible to some extent to make the spherical wave close to a plane wave and make it a convergent lens corresponding to a convex lens of an optical lens.

However, in the configuration of this convex lens-shaped acoustic lens, even if it approaches a plane wave, a plane wave can be obtained within a range of about the front projection area of the convex lens. Because of the diffusion, narrow directivity cannot be obtained as a result.

In other words, a spherical wave-like sound wave can be converted into a plane wave shape or a slightly convergent wave shape, and although a certain degree of directivity can be realized, it is difficult to realize a narrow directivity. It has been difficult to achieve a narrow directivity by a method of controlling a path without attenuating a sound wave scattered in a deviated direction.

[Object of the invention]

The present invention is intended to solve the above-described problem with respect to the directivity of the conventional speaker device. With a simple configuration, the present invention does not act on sound waves in the direction of the radiation axis, and does not act on sound waves in a direction deviating from the radiation axis. In addition, it is an object of the present invention to provide a speaker device capable of obtaining narrow directivity by increasing transmission loss.

[Summary of the Invention]

The present invention relates to a means of a speaker device for achieving the above object, and attenuates sound waves such as a thin plate of a porous sound absorbing material obtained by sintering aluminum, nickel, copper, or other metal powder on the front surface of a speaker. A plurality of sound-absorbing panels are provided in close proximity to a speaker, and the plurality of sound-absorbing panels are arranged at predetermined intervals in parallel with the radiation direction.

(Example of the invention)

Next, the principle of the present invention will be described with reference to FIG. 3 showing only one side from the center line.

Reference numeral 1 denotes a loudspeaker housed in the cabinet 4, and a component of a sound wave radiated from the front surface of the loudspeaker in the reference axis direction (in this figure, the radiation axis coincides with the center axis of the loudspeaker) passes through the gap of the sound absorbing panel 5 The user can reach the listening point as shown by the arrow (a).

On the other hand, an oblique arrow (b) deviating from the reference axis,
In the direction (c), the sound wave impinges on the sound absorbing panel, and when transmitting through the sound absorbing panel, a transmission loss occurs due to the sound absorbing property, and the sound pressure is attenuated.

At this time, since the number of times the sound absorbing panel 5 absorbs the sound in the direction of the arrow (c) more than the direction of the arrow (b), the attenuation amount increases.

That is, as the angle θ with respect to the reference axis increases, the amount of attenuation increases, and as a result, a loudspeaker device with a very narrow directivity can be obtained.

Note that there are optimal values for the interval d, length L, and width B of the sound absorbing panel 5 shown in FIGS. 1 and 2 depending on the frequency band to be handled, but generally have the following tendency.

d: It is preferably about 3 to 7 times the thickness t of the sound absorbing panel 5.

If the width is too narrow (the number of sheets is too large), the on-axis sound pressure will decrease, and the damping effect in the θ direction will level off.

L: A dimension is required such that sound waves in the angle θ direction to be attenuated pass through at least two or more sound absorbing panels 5.

However, as in the case of the above d, even if the number of sheets passing through is too large, the effect reaches a plateau. Therefore, it is preferable to set the length so that about 3 to 5 sheets pass.

B: About 1.5 to 3 times the diameter D of the speaker is good.

If it is small, the sound wave wraps around the sound absorbing panel 5 in the width direction, so that the attenuation effect is reduced. Particularly pronounced for low frequencies, one or more wavelength of the lowest frequency f _l at least handled is desirable.

As an example, the effect of the speaker device of the specifications in Table 1 is described in the fourth.
Shown in the figure.

This figure shows the attenuation due to the effect of the acoustic panel with respect to the reference axis when the reference axis in FIGS. 1 and 2 coincides with the center axis of the speaker.

Note that (1) shows the case where the sound absorption coefficient measurement in the reverberation room method is f = 1000 Hz and the back air layer is 50 mm.

Table 1 Speaker diameter D 110 mm Sound absorbing panel 5 Length L 165 mm Width B 250 mm Thickness t 3 mm Interval d 18 mm Number of sheets 24 Sound absorption coefficient α ⁽¹⁾ 0.91 Normal acoustic impedance Zn ⁽¹⁾ 780 (kg / m ² s) FIGS. 1 and 2 are for obtaining directivity in one horizontal or vertical direction using one speaker.

Further, in a speaker device such as a tone soil which obtains a narrow directivity by arranging a plurality of speakers in a straight line, a greater effect can be obtained by implementing the present invention.

That is, in an ordinary speaker device having a plurality of arrangements, sound waves having different phases overlap each other to cause interference and attenuate. Above, peaks and dips have a continuous characteristic.

In this case, as shown in FIG. 5 and FIG. 6, the sound absorbing panel 5 is provided at right angles to the arrangement axis of the speaker 1 to reduce the peak sound pressure and to obtain a narrow directivity speaker device having a small total peak and dip. It can be.

Further, in a speaker device in which a plurality of speakers having different bands are combined, as shown in FIGS. 7 and 8, the interval d, the length L, and the width of the sound absorbing panel 5 are partially adjusted according to the band of each speaker. B and the like may be different and combined.

Further, as shown in FIG. 9, a block having a necessary and sufficient thickness of a sound absorbing material 6 such as glass wool or foamed resin is arranged on both sides so as not to cover the front surface of the speaker 1, and the sound absorbing panel 5 of the present invention is provided. May be used in combination with.

In the above embodiment, the center axis of the speaker 1 and the reference axis of the sound absorbing panel 5 are matched, but as shown in FIG. Can also be provided.

In this case, the sound wave in the central axis direction is attenuated by the sound absorbing panel 5, but the sound wave in the reference axis direction does not attenuate because it passes through the interval between the sound absorbing panels 5, and it is as if the radiation axis were bent in this direction. And the direction of the directivity of the speaker device can be changed up and down or left and right.

Further, as shown in FIGS. 11 and 12, by arranging the sound absorbing panels 5 radially or convergently, it is possible to change the degree of directivity wide and narrow.

Further, as the material of the sound absorbing panel 5, in addition to a porous sound absorbing material obtained by sintering aluminum, nickel, copper, and other metal powders, a ceramic porous material or a fibrous sound absorbing material may also have the following sound absorbing properties, and If the strength is obtained, it can be used.

Sound absorption characteristics: In a required frequency band, the normal incidence sound absorption coefficient α is 0.5% or more on average, and the normal acoustic impedance Zn is on average not more than three times the acoustic impedance of air.

 However, it is the value when the air ratio behind is 50 mm.

Strength: At least one-tenth of the caliber of the speaker to be used must be strong enough to be independent.

〔The invention's effect〕

As described above, according to the present invention, it is not necessary to modify the speaker itself, and only by providing an acoustic panel in which a sound absorbing panel that attenuates sound waves and transmits the sound is provided in front, a narrow directivity can be obtained. In addition, the directional characteristics and the frequency characteristics can be changed depending on the size and arrangement of the sound absorbing panel.

Further, since the sound pressure frequency characteristics are hardly affected on the reference axis of the acoustic panel, the acoustic panel has features such as a reduction in efficiency and a decrease in sound quality.

[Brief description of the drawings]

1 and 2 are a side view and a front view of a basic configuration of an embodiment of the present invention, FIG. 3 is an explanatory view of the basic principle, and FIG. 4 is a view on the central axis of FIGS. 5 and 6 are side and front views of another embodiment, and FIGS. 7 and 8 are side and front views of the third embodiment. Fig. 9, Fig. 9 is a side view of the fourth embodiment, Figs. 10, 11, and 12 are side views of the fifth, sixth, and seventh embodiments, respectively. It is a side view. 1 ... speaker, 4 ... cabinet, 5 ... sound absorbing panel, 6 ... sound absorbing material.

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor guriya yasumo 4-2610 Hanazono, Tokorozawa City, Saitama Prefecture Pioneer Corporation Tokorozawa Plant (72) Inventor Naofumi Inkimi 1-1-6 Uchisaiwaicho, Chiyoda-ku, Tokyo Within Nippon Telegraph and Telephone Corporation (56) References Japanese Utility Model Showa 51-59244 (JP, U) Japanese Utility Model Showa 40-35286 (JP, Y1)

Claims (1)

(57) [Claims] A sound absorbing panel in which a plurality of sound attenuating panels are attenuated and transmitted in the direction of emission of sound waves radiated from at least one loudspeaker. A speaker device having directivity, comprising a panel.