JPS61135296A - Microphone - Google Patents

Abstract

PURPOSE:To obtain excellent sound quality and sharp directivity by providing a filter section selecting and outputting an output of a linear arrangement microphone having a short arranging length as the frequency gets higher. CONSTITUTION:Plural linearly arranged microphones having different length comprising plural microphone units 1b-1d are arranged in a line vertically on the floor while each end is arranged at the height of mouth of a talker (arranging section 1) and provided with a filter section 1a selecting and outputting the output of the linearly arranged microphones having a shorter length in the arrangement as the frequency gets higher. An output of a point C of the filter section 1a is extracted for low-frequency components only by an LPF9 and the output is added with an output of a point B whose low-frequency components are removed by an HPF10 by an adder 11. Then the synthesized output is eliminated for the high frequency component by the LPF12 and added with the high frequency component at a point A extracted by an HPF13 at an adder 14 to form an output D.

Description

[Detailed Description of the Invention] Industrial Application Field The present invention provides a microphone having donut-shaped directivity that is installed on the floor in the center of a round table conference hall and that can clearly pick up the voices of all attendees. It is related to.

Conventional technology In recent years, with the development of conference systems and teleconference systems that connect far-flung conference rooms with communication lines, speakers can speak without being aware of it, and are highly effective in eliminating ambient noise, reducing howling and noise. A strong microphone is desired.

In order to pick up sound without the speaker being aware of it, it is necessary to move the microphone away from the speaker. In this case, the power of the speaker's voice reaching the microphone decreases, and to compensate for this, linear array microphones, which have low inherent noise and are highly effective in removing ambient noise, have been attracting attention. This conventional technique includes, for example, Proceedings of the Acoustical Society of Japan, June 1988, P97-Pea.

Hereinafter, the conventional microphone as described above will be explained with reference to the drawings.

FIG. 4 shows the configuration of a conventional linear array microphone. In FIG. 4, reference numeral 41 indicates a microphone unit array section composed of a plurality of omnidirectional microphones (22) 41a, 42 indicates an adder, and 43 indicates an output terminal thereof.

The operation of the linear array microphone configured as described above will be described below.

Now, consider the case where the sound waves shown in FIG. 5 are incident on this linear array microphone. When a sound wave is incident from the direction 00 in FIG. 5, that is, from a direction perpendicular to the arrangement axis, the amplitude and phase of the sound pressure incident on all microphone units are equal. Therefore, the Kama Mugino output is amplified by the number of microphone units.

On the other hand, when sound waves are incident from the direction 900 in FIG. It does not appear in the later output. Therefore, this linear array microphone has a very sharp donut-shaped directional characteristic as shown in Figure 6 (b), and it is possible to pick up the voices of all attendees in a round table conference hall with just one microphone. . In FIG. 6(C), 4 is a speaker, 44 is a linearly arranged microphone, and the midpoint thereof is aligned with the center of sound emission from the speaker's mouth.

) in FIG. 6 shows the directional characteristics when the speaker 43 rotates around the center point of the linear array microphone 44, and 4
5 indicates a directional characteristic at low frequencies, and 46 indicates a directional characteristic at high frequencies. Because the wavelength of high frequencies is short, even if the speaker moves slightly from a straight line that is perpendicular to the array axis and passes through the center of the array, the phase of the sound pressure incident on each microphone unit will be different, resulting in a difference in addition. They cancel each other out, resulting in sharp directivity.

Problems to be Solved by the Invention However, in actual conference systems and telecombination systems, the linearly arranged microphones having the configuration shown in Fig. 4 are arranged at the height of the speaker's mouth as shown in Fig. 6.4. Match the centers. In other words, the method of locating the microphone unit at the position where the sensitivity is maximum causes a serious visual problem.

To solve the visual problem, see Figure 7 (c).
usage is required. In other words, the upper end of the linear array microphone should be at the level of the speaker's mouth or below the line of sight, so that the speaker does not get in the way of meeting attendees located on the other side of the linear array microphone, or when looking at a blackboard, TV screen, etc. It is necessary to take this into account. When used in this way with the conventional linear array microphone shown in Figure 4,
(in Fig. 7).

FIG. 7(B) shows the directional characteristics when the upper end of the linear array microphone 44 is positioned at the height of the speaker's mouth, and 47.48 shows the directional characteristics when the upper end of the linear array microphone 44 is located at the height of the speaker's mouth. These are the low frequency and high frequency to directional characteristics when the speaker 43 rotates. Because of this directional characteristic, in the conventional linear array microphone, when used as shown in Figure 7 (5), the direction in which the sensitivity of the directional characteristic 48 at high frequencies is large and the direction toward the actual speaker's mouth are large. This has led to the problem that only very poor sound quality can be collected due to the lack of high frequency components.

In view of the above problems, the present invention realizes excellent sound quality and sharp directivity even when the upper end of the microphone is installed at the height of the speaker's mouth, as shown in Figure 7 (c). Liru. It provides microphones for conference systems and teleconference systems.

Means for Solving the Problems In order to solve the above problems, each of the microphones of the present invention is composed of a plurality of microphone units,
and an array section in which a plurality of linearly arrayed microphones having different total array lengths in whole or in part are arranged with one end aligned at a certain height and arranged perpendicularly to the floor direction and on the same straight line, and an array section that is arranged as the frequency increases. It consists of a filter section that selects and outputs the output of a linearly arranged microphore with a short overall length.

Effects The present invention achieves sufficiently sharp directivity characteristics at low frequencies by using the distance from the height of the speaker's mouth to the floor as the total length of the linear array microphone. Finally, for high frequencies, the overall length of the array is shortened, and the array is constructed with the upper part of the 7 microphones that can be arranged, and the center of the array is brought closer to the height of the speaker's mouth, as described in the conventional example. This prevents sensitivity attenuation with respect to the direction of the speaker at high frequencies, making it possible to collect sound with sharp directional characteristics and excellent sound quality in an inconspicuous installation form.

EXAMPLE Hereinafter, a microphone according to an example of the invention will be described with reference to the drawings. FIG. 1 shows the configuration of a microphone in a first embodiment of the present invention. In FIG. 1, reference numeral 1 indicates an array section composed of a plurality of omnidirectional microphone units, and reference numeral 1a indicates a filter section. 2 is array part 1
3 is a first adder that adds the outputs of the eight microphone units 1b at the top, 3 is a second adder that adds the outputs of the eight microphone units 1C immediately below it, and 4 is the bottom 1 adder.
6 microphones (22)) 3rd to add the outputs of 1d
6 is a fourth adder that adds the outputs of the first adder 2 and the second adder 3; 6 is the output of the fourth adder 6 and the third adder 4; a fifth adder for summing the outputs;
7 is a first amplifier that amplifies the output of the second adder 2;
is a second amplifier that amplifies the output of the third adder 6, 9 is a first low-pass filter that extracts only the low frequency component of the sixth adder 6, and 10 is equal to the cutoff frequency of this low-pass filter. a second frequency having a cutoff frequency;
A first bypass filter 11 extracts only the high-frequency component of the output of the amplifier 8, and a sixth bypass filter 11 adds the output of the first low-pass filter 9 and the output of the first bypass filter 10.
adder, 12 is the first low-pass filter 9 to jl
A second low-pass filter having a cutoff frequency higher than the cutoff frequency of the HcD bypass filter 10, 13 a second bypass filter having the same cutoff frequency as the second low-pass filter 12, and 14 a second low-pass filter. This is a seventh adder that adds the outputs of the filter 12 and the second bypass filter 13.

The operation of the microphone configured as described above will be described below with reference to FIGS. 1 and 2.

Figure 2 shows the directivity characteristics of the output of each part in Figure 1 under the conditions of Figure 7 and 4. In Figure 2, 16 is A in Figure 1.
16 shows the directional characteristic of the output of point B in FIG. 1, 17 shows the directional characteristic of the output of point 0 in FIG. 1, and 18 shows the directional characteristic of the output of point D in FIG. 0The output at point A in Figure 1 is the sum of the outputs from the top eight of the 32 microphone units and multiplied by 4, and the output at point B is the sum of the outputs from the top 16 microphone units. The output at point 0 is the sum of all 32 microphone units. Therefore, the outputs from points A, B, and C can be regarded as three linearly arranged microphones of different lengths, with one end aligned with the top of the microphone. A,
B, the directional characteristics at point 0 are significantly different. Looking at the directional characteristic 17 in FIG. 2, which is the output of point 0, the directional characteristic 26 at low frequencies ensures sufficient sensitivity toward the direction of the speaker's mouth, and its directivity is also sharp. However, the mid-range frequency,
The directional characteristic of 26°27 at high frequencies has a markedly reduced sensitivity toward the direction of the speaker's mouth.

Looking at the directional characteristic 16 in Fig. 2, which is the directional characteristic of the output from point B in Fig. 1, the output from point B has a total array length of 0 in Fig. 1.
Since the center of the array is much closer to the height of the speaker's mouth, the directivity characteristic 23 in the mid-range frequency is revised, but the directivity in the low-frequency range is 1/2 that of the point. It can be seen that the characteristic 22 has deteriorated on the contrary, and the directivity characteristic at high frequencies is still poor. Furthermore, in the output from point A in Figure 1, where the total length of the array is shortened and the array center approaches the height of the speaker's mouth, only the directional characteristic 21 in the high frequency range is observed, as seen in the directional characteristic 16 in Figure 2. It can be seen that the directivity characteristics are excellent, and the directional characteristics of 19°20 at low and middle frequencies are poor.

Therefore, in this embodiment, a filter is used to extract and synthesize only the low frequency from the output of point 0, only the middle frequency from the output of point B, and only the high frequency from the output of point A. As shown in directional characteristic 18 in Figure 2, the output at point D, which is the output of The characteristics are realized.

In other words, in Figure 1, only the low frequency component of the output at point 0 is extracted by the first low-pass filter 9, and
A sixth adder 11 adds the output of point B, from which low frequency components have been removed by the bypass filter. Next, the high frequency component of this composite output is removed by the second low-pass filter 12, and the high frequency component of point A extracted by the second bypass filter 13 is added with the high frequency component of the point A, and the result is output by a seventh adder. 1st
The first amplifier 7 and the second amplifier 8 in the figure add the outputs of 8 microphone units in the high-frequency linear array microphone section and 16 microphone unit outputs in the mid-range linear array microphone section. In this example, the sensitivity does not match the sum of the 32 low-frequency amplifiers, so this is an amplifier inserted to correct the sensitivity.

As described above, according to this embodiment, the upper end of the linear array microphone is set at the height of the speaker's mouth, the distance to the floor is the total length of the array at low frequencies, and the total length of the array is shortened as the frequency increases. By configuring the microphone to be located as high as possible in the array, the presence of the microphone in a conference or teleconference system is completely unnoticeable, and excellent sound quality and sharp donut-shaped directivity are achieved over the entire frequency range. It is possible to create a microphone with

Also, like a normal linear array microphone, a high signal-to-noise ratio is ensured, and one microphone can be installed in the center of a round table conference room to collect the sounds of all the surrounding attendees.

A second embodiment of the present invention will be described below with reference to the drawings.

FIG. 3 is a configuration diagram of a microphone showing a second embodiment of the present invention.

In FIG. 3, numeral 31 is an array section composed of a plurality of omnidirectional microphone units, and 31a is a filter section. 32 is a first adder that adds each output of the microphone unit 31b; 33 is a microphone unit 31;
A second adder 34 adds half of the output of the microphone unit 31b and the output of the microphone unit 31b, and a third adder 34 adds the output of half of the microphone unit 31b and the output of the microphone units 31c and 31d. , 35 is a first low-pass filter, 36 is a first bypass filter, 37 is a second low-pass filter of Hori 4's addition m6.3BId, 39 is a jI2 bypass filter, 40
is a fifth adder that adds the outputs of the second low-pass filter 38 and the second bypass filter 39, and 41 is its output terminal.

The operation of the microphone configured as described above will be explained below.

The configuration shown in Figure 3 is similar to the configuration shown in Figure 1, in which three linear array microphones with different overall lengths are combined, but the lower the linear array microphone section, the longer the interval between the microphone units. It is distinctive in what it does. By adopting such a configuration, excellent S/R up to the high frequency band can be achieved with a small number of microphone units.
A microphone having N can be realized. That is, the first
In the configuration shown in the figure, 32 microphone units are used, and at low frequencies, the outputs of all 32 microphone units are added together to obtain the output, and the S/N is the S/N of one microphone unit. It becomes 51 times. At the mid-range frequency, 16 additions are output, so the number is Fτ times. However, at high frequencies, only eight additions are performed, resulting in only a sevenfold increase, which is insufficient. - In the configuration shown in Figure 3, the output is obtained by adding the outputs of 17 microphone units for the linearly arranged microphones in the low, mid, and high range sections, and the S/N is calculated by adding up the outputs of the 17 microphone units. The S/N ratio of the microphone unit is r times superior. Furthermore, the total number of microphone units used is 33, which is almost the same as in the case of FIG. The outputs of these three linearly arranged microphone sections are sent to a first adder 32, a second adder 33, and so on. The signal is output from the third adder 34, and the subsequent synthesis procedure is exactly the same as that described for the configuration of FIG.

As described above, by devising the method of arranging the microphone units and the method of extracting the output, it is possible to realize an excellent S/N ratio over the entire frequency band with the minimum number of microphone units necessary.

In both the first example and the second example, the total length of the array is controlled in three stages, but if necessary, the total length of the array may be controlled more precisely.

Effects of the Invention As described above, the present invention provides a plurality of linear array microphones each having a different array length, each consisting of a plurality of microphone units, placed vertically on the floor with one end aligned at the height of the speaker's mouth. an array section arranged on the same straight line in the direction;
By configuring a filter section that selects and outputs the output of a linear array microphone with a shorter overall array length as the frequency increases, it is possible to achieve sharp toroidal directivity and excellent sound quality over the entire frequency range with an inconspicuous installation. This microphone has excellent signal-to-noise ratio (S/N) and can be installed on the floor above a round table in a conference system or teleconference system, and can be used by all attendees without the speaker being aware of it. It is possible to configure a system that can clearly pick up people's voices and is resistant to howling.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram of a microphone according to a first embodiment of the present invention, FIG. 2 is a directional characteristic diagram at each point in FIG. 1, and FIG. 3 is a configuration diagram of a microphone according to a second embodiment of the present invention. , FIG. 4 is a configuration diagram of a conventional microphone, FIG. 6 is an explanatory diagram of the operation of FIG. 4, and FIG. 6 (c) and FIG. 6) and FIG. 7(B) are the same directivity characteristic diagrams. 1.31...Array part, 1a, 31a...
・Filter section. Name of agent: Patent attorney Toshio Nakao and 1 other person 2nd
figure

Claims (1)

[Claims] A plurality of linearly arranged microphones each consisting of a plurality of microphone units and having different total array lengths in whole or in part are arranged perpendicularly to the floor and on the same straight line with one end aligned at a certain height. and a filter section that selects and outputs the output of a linear array microphone whose total array length becomes shorter as the frequency increases.