JPH0667022B2 - Microphone - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Industrial Field of the Invention The present invention is installed on the floor in the center of a round-table conference room and has a donut-shaped directivity microphone for clearly collecting the sounds of all attendees. It is about.

2. Description of the Related Art In recent years, with the development of conference systems and teleconferencing systems that connect distant conference rooms with communication lines, microphones that can speak without being conscious of the speaker and have a high effect of removing ambient noise and strong against howling Is desired.

In order to pick up the sound without making the speaker conscious, it is necessary to keep the microphone away from the speaker. In this case, the voice power of the speaker reaching the microphone is reduced, and in order to cover the voice power, a linear array type microphone that has a small inherent noise and a high effect of removing ambient noise has been attracting attention. As this conventional technique, for example, there are P97 to P98, Proceedings of the Acoustical Society of Japan, May 1980.

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

FIG. 4 shows the structure of a conventional linear array microphone. In FIG. 4, reference numeral 41 is a microphone unit array portion composed of a plurality of omnidirectional microphone units 41a, 42 is an adder, and 43 is 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 wave shown in FIG. 5 is incident on this linear array microphone. When sound waves are incident from the 0 ° direction in FIG. 5, that is, from the direction perpendicular to the array axis, the amplitude and phase of the sound pressure incident on all microphone units become equal. Therefore, the output after addition is amplified by the number of microphone units.

On the other hand, when sound waves are incident from the direction of 90 ° in FIG. 5, that is, the direction of the array axis, the phases of the sound pressures that are incident on the microphone units are different, and the outputs are canceled by addition, and the output after addition is obtained. Does not come out. Therefore, with this linear array microphone, a very sharp donut-shaped directional characteristic is obtained as shown in FIG. 6 (B), and it is possible to collect the voices of all the attendees with this single microphone at the round-table conference hall. . In addition, 4 in FIG. 6 (A)
3 is a speaker, and 44 is a linear array microphone, and its midpoint is made to coincide with the center of sound emission from the speaker's mouth.

FIG. 6 (B) shows the directional characteristics when the speaker 43 rotates around the midpoint of the linear array microphones 44.
Reference numeral 5 indicates a directional characteristic at a low frequency, and 46 indicates a directional characteristic at a high frequency. Since the wavelength is short in the high frequency range, the phase of the sound pressure incident on each microphone unit is different 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, and cancels each other by addition. As a result, sharp directivity is obtained.

Problems to be Solved by the Invention However, in an actual conference system or a teleconference system, the linear array microphones having the configuration shown in FIG. 4 are arranged at the speaker's mouth level as shown in FIG. 6 (A). Match the centers. That is, the method of installing the microphone at the position where the sensitivity is maximized causes a great visual problem.
Therefore, in order to solve the visual problem, the usage of FIG. 7 (A) is required. That is, the upper end of the linear array microphone is about the mouth level below the line of sight of the speaker, and the speaker is a conference participant located on the other side of the linear array microphone.
Alternatively, it is necessary to give consideration so as not to disturb the viewer when viewing a blackboard or TV screen. When the conventional linear array microphone shown in FIG. 4 is used in this way, the directional characteristic shown in FIG. 7 (B) is obtained.

FIG. 7 (B) shows the directional characteristics when the upper end of the linear array microphone 44 is located at the mouth level of the speaker 43. 47 and 48 center around the upper end of the linear array microphone 44. It is a low frequency and a high frequency directional characteristic when the speaker 43 rotates. From this directional characteristic, in the conventional linear array microphone, when the usage of FIG. 7 (A) is used, the direction in which the sensitivity of the directional characteristic 48 is high at high frequencies and the direction of the actual speaker's mouth are large. Therefore, there is a problem that only high-frequency components are deficient and only extremely poor sound quality can be collected.

In view of the above problems, the present invention realizes excellent sound quality and sharp directivity even if the upper end of the microphone is installed at the level of the speaker's mouth as shown in FIG. 7 (A). It is possible to provide a microphone for a conference system or a teleconference system.

Means for Solving the Problems In order to solve the above problems, the microphone of the present invention is
A plurality of linear array microphones, each of which has a plurality of microphone units and an adder and which are arranged vertically on the same straight line with their upper ends aligned and on the same straight line, and have different array lengths, and the plurality of the arrayed microphones. The output of the linear array microphone of is input, the low frequency component is extracted from the linear array microphone with a long array length, and the high frequency component is the linear array microphone with a short array length, The filter unit is adjusted so that it is taken out from the output.

Operation The present invention realizes a sufficiently sharp directional characteristic by using the distance from the speaker's mouth height to the floor as the entire length of the linear array microphone in the low frequency range by the above configuration. In the high frequency range, the total length of the array is made short, and the array is configured as above the microphone as possible to bring the center of the array close to the mouth level of the speaker. It is possible to pick up the sound with excellent directivity and sharp directional characteristics by preventing the sensitivity from being attenuated in the direction of the person.

Embodiment A microphone according to an embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows the structure of a microphone according to the first embodiment of the present invention. In FIG. 1, reference numeral 1 is an array section composed of a plurality of omnidirectional microphone units, and 1a is a filter section. 2 is the array part 1
A first adder 3 for adding the outputs of the upper eight microphone units 1b, a second adder 3 for adding the outputs of the lower eight microphone units 1c, and a lower one 1
Third addition of the outputs of the six microphone units 1d
5 is a fourth adder for adding the outputs of the first adder 2 and the second adder 3, and 6 is the output of the fourth adder 5 and the third adder 4. A fifth adder for adding the outputs,
7 is a first amplifier for amplifying the output of the first adder 2, 8
Is a second amplifier for amplifying the output of the third adder 5, 9 is a first low-pass filter for extracting only the low-frequency component of the fifth adder 6, and 10 is equal to the cut-off frequency of this low-pass filter Second, with cutoff frequency
A first high-pass filter for taking out only the high-frequency component of the output of the amplifier 8 of No. 6, a sixth for adding the output of the first low-pass filter 9 and the output of the first high-pass filter 10
Of the first low-pass filter 9 and the first low-pass filter 9
Second low-pass filter having a cut-off frequency higher than that of the high-pass filter 10 of
Reference numeral 3 is a second high-pass filter having the same cutoff frequency as that of the second low-pass filter 12, and 14 is a seventh adder for adding the outputs of the second low-pass filter 12 and the second high-pass filter 13.

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

FIG. 2 shows the directional characteristics of the output of each part of FIG. 1 under the condition of FIG. 7 (A). In FIG. 2, 15 is the directional characteristic of the output at the point A of FIG. 1, and 16 is The directivity of the output at point B in FIG. 1, the directivity of the output at point C in FIG. 1, and the directivity of the output at point D in FIG. The output at point A in Fig. 1 is the sum of the eight outputs in the upper part of the 32 microphone units and is multiplied by 4. The output at point B is the sum of the outputs from the 16 microphone units from the upper end. 2
The output at point C is the sum of all 32 microphone units. Therefore, the outputs at the points A, B, and C can be regarded as three linear array microphones having different lengths, one end of which is aligned with the upper end of the microphone, and as shown in FIG. The directional characteristics at points A, B, and C are greatly different. Looking at the directivity characteristic 17 of FIG. 2 which is the output at the point C, the directivity characteristic 25 at the low frequency range has sufficient sensitivity in the direction of the speaker's mouth and its directivity is also sharp. However, the directional characteristics 26 and 27 at the mid-range frequencies and the high-range frequencies show a marked decrease in the sensitivity in the direction of the speaker's mouth.

Looking at the directivity characteristic 16 of FIG. 2 which is the directivity characteristic of the output of the point B of FIG. 1, the output of the point B has the entire array length C of FIG.
Since the center of the array is closer to the speaker's mouth height, the directional characteristic 23 at the mid frequency is improved, but the directional characteristic 22 at the low frequency is rather changed. It can be seen that the directional characteristic deteriorates and the directional characteristics at high frequencies are still poor. Furthermore, the entire sequence becomes shorter,
At the output at the point A in FIG. 1 where the center of the array is close to the mouth level of the speaker, as shown in the directional pattern 15 in FIG. It can be seen that the directional characteristics 19 and 20 at the range frequency are bad.

Therefore, in this embodiment, by using a filter, only the low frequency is output from the output of the point C, only the intermediate frequency is output from the output of the point B, and only the high frequency is output from the output of the point A, and the output of the microphone is output. As shown in the directivity characteristic 18 in FIG. 2, the output at the point D has excellent directivity characteristics with high sensitivity in the direction of the speaker's mouth over all frequencies and low sensitivity to sound waves from above and below. Has been realized.

That is, in the output at point C in FIG. 1, only the low-frequency component is extracted by the first low-pass filter 9,
The output at point B from which the low-frequency components have been removed by the high-pass filter of No. 2 and the sixth adder 11 are added. Next, the synthesized output has the high-frequency component removed by the second low-pass filter 12, and the high-frequency component at point A extracted by the second high-pass filter 13 is added by the seventh adder to produce an output. First
The first amplifier 7 and the second amplifier 8 in the figure add eight microphone unit outputs in the linear array microphone section for the high frequency range and 16 microphones in the linear array microphone section for the middle frequency range, and they are added as they are. In this case, since the sensitivity does not match the one obtained by adding the 32 low-frequency bands, the amplifier is inserted for sensitivity correction.

As described above, according to the present embodiment, the upper end of the linear array type microphone is the height of the speaker's mouth, the distance to the floor is the total array length at low frequencies, and the overall array length is shortened as the frequency increases. , And by arranging the array so that it is located as high as possible, it makes the presence of the microphone inconspicuous in the conference system or the teleconference system, and provides a microphone with excellent sound quality and sharp donut-shaped directivity over the entire frequency band. realizable.

In addition, a high S / N ratio is secured as in the case of a normal linear array microphone, and this one can be installed in the center of the round table conference room to collect the sounds of all the attendees in the surrounding area.

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

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

In FIG. 3, reference 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 for adding the respective outputs of the microphone unit 31b, and 33 is the microphone unit 31
A second adder for adding the output of c and half of the outputs of the microphone unit 31b, 34 is a third adder for adding the output of half of the microphone units 31b and the outputs of the microphone units 31c, 31d. Adder, 35 is a first low-pass filter, 36 is a first high-pass filter, 37 is a fourth adder, 38 is a second low-pass filter, 39 is a second high-pass filter, 40 is a second low-pass filter A fifth adder 41 for adding the outputs of 38 and the second high-pass filter 39 is an output terminal thereof. The operation of the microphone configured as described above will be described below.

Similar to the configuration of FIG. 1, the configuration of FIG. 3 is a configuration in which three linear array microphones having different array lengths are combined, but the array intervals of the microphone units are made longer as the linear array microphone section in the lower frequency band is increased. There is a feature in doing it. With such a configuration, it is possible to achieve excellent S / S up to a high frequency band 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 the low frequency, the outputs of all 32 microphone units are added to obtain an output, and the S / N thereof is the S / N of one microphone unit. become. Since 16 additions are output at mid frequency become. However, at high frequencies only 8 additions are made Not only was it insufficient. On the other hand, in the configuration shown in FIG.
The output of each microphone unit is added as an output, and the S / N is the S / N of one microphone unit over all frequency bands. And will be excellent. Moreover, 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 linear array microphones are
First adder 32, second adder 33, third adder 3
4 and the subsequent synthesizing procedure is exactly the same as that described in the configuration of FIG.

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

In addition, although the first embodiment and the second embodiment are controlled in three steps of the total length of the sequence, a finer control of the total length of the sequence may be performed if necessary.

EFFECTS OF THE INVENTION As described above, according to the present invention, a plurality of microphone units and adders, which are vertically aligned in the floor direction and aligned on the same straight line with their upper ends aligned and each having a different total array length, are arranged. The linear array microphones of this book and the outputs of the plurality of linear array microphones are input, the low-frequency component is extracted from the linear array microphone with a long array length, and the high-frequency component is a linear array microphone with a short array length. In addition, it has a sharp donut-shaped directional characteristic and excellent sound quality over the entire frequency band in an inconspicuous installation state by being configured with a filter section adjusted so that it can be taken out from the output of the linear array microphone arranged above. In addition, a microphone with excellent S / N ratio can be realized, and it can be used in conference systems and teleconference systems. Installed on the floor of a round-table conference, this one can clearly pick up the voices of all attendees without making the speaker aware, and a system that is strong against howling can be configured.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a microphone according to the first embodiment of the present invention, FIG. 2 is a directional characteristic diagram at each point of FIG. 1, and FIG. 3 is a configuration diagram of a microphone according to the second embodiment of the present invention. , FIG. 4 is a configuration diagram of a conventional microphone, FIG. 5 is an operation explanatory diagram of FIG. 4, and FIG. 6 (A) and FIG. 7 (A) are layout diagrams of microphones for explaining usage. FIG. 6 (B) and FIG. 7 (B) are directivity characteristic diagrams. 1, 31 ... Array part, 1a, 31a ... Filter part.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-58-151796 (JP, A) JP-A-59-149494 (JP, A) Actual development Sho-59-114696 (JP, U)

Claims (1)

[Claims] 1. A plurality of microphone units and an adder for adding the outputs of the microphone units, which are arranged on the same straight line in a direction perpendicular to the floor with their upper ends aligned, and have different array lengths. A plurality of linear array microphones, the outputs of the plurality of linear array microphones are input,
A low-frequency component is extracted from a linear array microphone with a long array length, and a high-frequency component is a linear array microphone with a short array length, and is a filter adjusted so as to be extracted from the output of a linear array microphone arranged above. A microphone composed of a part and a part.