JPH05103391A - Directivity-controlled loudspeaker system - Google Patents

Abstract

PURPOSE:To provide an excellent directivity-controlled loudspeaker system by providing plural loudspeaker units arranged in nearly a line or plane and devices which input signals to which a prescribed load function is applied to the units. CONSTITUTION:In case loudspeaker units 1 are linearly arranged at regular intervals of, for example, 15cm, amplifiers 2 are provided to each loudspeaker pair at the same distance from the center and input level (gain) setters 3 are connected to a signal source 4. In addition, the equation shown in the figure is used as the load function applied to the input level of each unit 1. When the function is set so that the function can become the cosine function of n=1, the frequency characteristic in the service area becomes flat and, in addition, the side lobe outside the service area becomes lower. The value of the (n) is not restricted to '1', but can be set to an arbitrary positive number. Therefore, when such a load function is applied that the level at its central section is higher and level at its peripheral section is lower, the contribution from the speaker unit at the peripheral section becomes lower.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a directional control speaker system having a flat frequency characteristic in a service area and a small side lobe outside the service area.

[0002]

2. Description of the Related Art In recent years, in museums and showrooms, there is an extremely great demand for transmitting sound only to a limited area, such as making it possible for those who are viewing the exhibition to hear the explanation. there were. Conventionally, as such a speaker, there are a method using a horn speaker, a method using a parametric speaker, a method using a phased array speaker such as a tone distortion speaker, and the like.

In actual use, however, simply sharpening the directivity narrows the service area, making it impossible to service a large number of listeners. Therefore, there is a demand for a speaker system that has a sound pressure distribution that is as uniform as possible within the service area and that exhibits steep attenuation outside the service area.

A conventional directivity control speaker system will be described below with reference to the drawings. FIG. 5 shows an example of a tone zoning system in which 12 speaker units 1 each having a diameter of 8 cm are arranged in an array on a straight line at intervals of 15 cm (5 units are shown in the figure). In consideration of the actual usage conditions, the speaker system is mounted on a ceiling surface having a height of 3 m, and the listener passes under the speaker system. As a directivity, the horizontal plane (x-y) at the listener's ear height is used. Consider the sound pressure distribution on a plane. FIG. 6 shows the directional characteristics in the y-axis direction when signals of the same phase and the same level are input to these speaker units.

Next, a speaker system using several band-divided speaker units will be described with reference to FIG. When four speaker units are arranged so that the outer two spaces are d and the inner two spaces are d / 4, fc / 2 to 2fc of the frequency fc whose wavelength is the distance d It is known that a smooth directional characteristic without side lobes can be obtained in the band. For example, the directional characteristics when two speaker units are installed at 15 cm intervals are as shown in FIG. 8, and at 1.25 kHz, it is possible to obtain a small and sharp directivity as compared with the tone distortion system shown in FIG.

[0006]

However, as shown in FIG. 6, in the above-described conventional tone-zone type speaker system, a sharp directivity cannot be obtained for its size, and the sound pressure level outside the service area is sufficiently small. There was the problem of not looking down. On the other hand, in the system using several sets of band-divided speaker units, as shown in FIG. 8, a small and sharp directivity is obtained in the low range, but a large side lobe occurs in the high range. Further, there is a problem that the directional characteristic changes due to the phase change due to the network for dividing the band.

The present invention solves the above-mentioned conventional problems, and an object thereof is to provide a directional control speaker system which is small in size, has a flat frequency characteristic in the service area, and has a small side lobe outside the service area. And

[0008]

In order to achieve the above object, the directional control speaker system of the present invention applies a plurality of speaker units and a load function to the speaker units such that the central portion is larger and the peripheral portion is smaller. It has a configuration for inputting the input signal.

[0009]

According to the present invention, since the sound pressure at a certain point in the space is obtained by synthesizing the sounds from the speaker units, the present invention provides a load function for each speaker unit such that the central portion is larger and the peripheral portion is smaller. As a result of inputting the applied signals and obtaining the respective sound pressure distributions, it is possible to obtain a directivity with a smaller size and flatter frequency characteristics in the service area than before, and a small side lobe outside the service area.

[0010]

EXAMPLE 1 Example 1 of the present invention will be described below with reference to FIG.

As shown in FIG. 1, the speaker unit 1
12 are arranged linearly at intervals of 15 cm (only 5 are shown). An amplifier 2 is provided for each pair of speaker units equidistant from the center, and an input level (gain) setter 3 is connected to a signal source 4. Here, the load function applied to the input level to each speaker unit is represented by the equation (4).

[0012]

[Equation 4]

FIG. 2 shows the directional characteristic when the cosine function of n = 1 is set. The full width 2l of the speaker system is the same as in the case of FIG. 7, but the frequency characteristic in the service area is flat and the side lobe level outside the service area is small. Note that n is not limited to 1 and may be any positive number.

(Embodiment 2) In all of the following embodiments, the arrangement of the speaker units 1 is the same as that of the first embodiment, but the weighting function applied to the signal input level to each speaker unit 1 is different. As a second embodiment, the load function is the expression shown in (Equation 5).

[0015]

[Equation 5]

Here, the directional characteristics when m = 2 and N = 1 are shown in FIG. The side lobe at high frequencies is smaller than that in the case of the cosine function of the first embodiment, and the attenuation characteristic is smooth. Note that m and N may be any positive numbers.

(Embodiment 3) The load function of the third embodiment is represented by the equation (6).

[0018]

[Equation 6]

Here, in the Bessel function of the first kind J ₀
The case of (α ₁ ) = 0 was used. Also in this case, a smooth attenuation characteristic with a smaller side lobe was obtained than in the case of the first embodiment. Note that generally, the same result is obtained when J ₀ (α _{2n + 1} ) = 0.

(Fourth Embodiment) A fourth embodiment will be described with reference to FIG. In this embodiment, 30 speaker units are linearly arranged at 15 cm intervals, and a signal obtained by applying a weighting function when m = 2 and N = 3 in (Equation 5) is input to each unit. There is. The input level to each unit is the characteristic No. of (Table 1). The value shown in A is used.

[0021]

[Table 1]

As described above, in the case of the load function in which the level of the central portion is high and the level of the peripheral portion is low, the contribution from the speaker unit in the peripheral portion becomes small. Therefore, FIG. 4 shows a change in directional characteristics when the input to the speaker unit in the peripheral portion is set to 0 (corresponding to a reduction in the overall width of the speaker system). The characteristic curves A to D in FIG. 4 are characteristic No. 1s having input levels (Table 1) to each unit. This is the case of the values shown in A to D. From this result, when the input level is 0.2 or less for the central unit, the side lobe can be suppressed to -25 dB or less even if the input level of the unit is set to 0, and the influence on the directional characteristics is small, but 0.2 In the above case, the service area becomes smaller and the side lobe becomes larger.

In the above-mentioned embodiments, the case where they are arranged linearly has been described, but it is natural that the same effect can be obtained when they are arranged in a plane.

[0024]

As is apparent from the above embodiments, the present invention inputs a plurality of speaker units arranged substantially linearly or in a plane and a signal obtained by applying a predetermined load function to these speaker units. By providing the means, it is possible to realize an excellent directional control speaker system having a flat frequency characteristic in the service area and a steep attenuation characteristic with a small side lobe outside the service area.

[Brief description of drawings]

FIG. 1 is a block diagram of a directional control speaker system according to a first embodiment of the present invention.

FIG. 2 is a directional characteristic diagram of the same embodiment.

FIG. 3 is a directional characteristic diagram of the second embodiment.

FIG. 4 is a directional characteristic diagram of the fourth embodiment.

FIG. 5 is a block diagram of a conventional tone-zone type speaker system.

FIG. 6 is a directional characteristic diagram of the same system.

FIG. 7 is a configuration diagram of another example of a conventional directional control speaker system.

FIG. 8 is a directional pattern diagram when two speaker units are used.

[Explanation of symbols]

 1 Speaker unit 2 Amplifier 3 Input level setter 4 Signal source

Claims (6)

[Claims] 1. A level setting for arranging a plurality of speaker units at substantially equal intervals, dividing the speaker unit into a plurality of substantially concentric channels, and inputting a signal applied with a predetermined weighting function to each channel. And a directivity control speaker system in which the value of the load function is set so that the input level to each channel is higher in the central part and lower in the peripheral part. 2. A weighting function applied to signals input to a plurality of speaker units is as follows: The directional control speaker system according to claim 1, represented by: 3. A weighting function applied to signals input to a plurality of speaker units is as follows: The directional control speaker system according to claim 1, represented by: 4. A weight function applied to signals input to a plurality of speaker units is expressed by (Equation 2), and a numerical value of either m = 1 or 2 and N = 1, 2, 3, ... The directional control speaker system according to claim 1, wherein the directional control speaker system is any one of the values. 5. A weighting function applied to signals input to a plurality of speaker units is as follows: The directional control speaker system according to claim 1, represented by: 6. A plurality of speaker units arranged at substantially equal intervals are divided into a plurality of channels so that the smallest level among the input levels to each channel has an upper limit of 20% with respect to the largest level. Distributed directional control speaker system.