JPH0320200B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a microphone chamber in which the characteristics of a directional microphone are less likely to change when an object is placed near the microphone chamber.

[Conventional technology]

Figures 14a and 14b are perspective views and partial sectional views showing the mounting structure of a microphone (hereinafter referred to as microphone) chamber in a conventional loudspeaker telephone;
3 is a perspective view of the microphone support bottom plate shown in the figure; in these figures, 1 is the handset, 2 is the base set, and
is a speaker, 4 is a slit wall on the top surface, 5 is a slit wall on the front surface, 6 is a slit wall on the side surface, 7 is a directional microphone, 8 is a support bottom plate for the directional microphone 7, 9
10 is a side wall at the rear of the microphone chamber, 10 is a side wall at the side of the microphone chamber, and 11 is a side wall at the bottom of the microphone chamber.

In a public address telephone, since it is important for performance to reduce the acoustic coupling from the speaker 3 to the directional microphone 7 as much as possible, conventionally the speaker 3 is mounted behind the directional microphone 7 as shown in FIG. The directional microphone 7 obtains directional characteristics by controlling the sound entering from the front and rear surfaces of the diaphragm in a free sound field, so conventionally, the microphone room was constructed using a As shown in Publication No. 57-50861 "Directional Microphone Built-in Loudspeaker Telephone", slit walls 4, 5, 6 are provided with holes passing through the microphone chamber and the outside of the microphone chamber, side walls 9, 10 without holes, 11.

[Problem that the invention seeks to solve]

The conventional microphone room as described above has 4 slit walls.
and side wall 11, slit wall 5 and side wall 9, and slit wall 6 and side wall 10 are composed of substantially parallel surfaces, so a loudspeaker telephone is installed on a shelf etc. , objects (box board, shelf board,
When a hand, etc.) is placed, the object surface on which it is placed and the opposing side wall surfaces 9, 10, 11 become parallel, so
Noise Countermeasures Handbook (published by Gihodo) Volume 2
As shown in 3.2.1.c, the sound is reflected infinitely, and a synthesized sound of these reflected sounds is input to the rear surface of the diaphragm of the directional microphone 7. On the other hand, the front surface of the diaphragm of the directional microphone 7 receives sound close to direct sound with little influence from the reflecting surface. The directional microphone 7 is
The design is such that the directivity is the sharpest when the same direct sound is input from the front and rear sides of the diaphragm, so if the loudspeaker telephone is installed under these conditions, the directivity will deteriorate significantly. There was a problem with that. In the loudspeaker telephones shown in FIGS. 14a and 14b, the directional characteristics of the directional microphone 7 deteriorate significantly, and the amount of acoustic coupling from the speaker 3 to the directional microphone 7 increases, causing howling. Therefore, the insertion loss of the audio switch is reduced. had to increase.

For this reason, it has been difficult to realize a loudspeaker telephone with good simultaneous call performance.

The present invention has been made to eliminate these drawbacks, and an object of the present invention is to provide a microphone room for a public address telephone with a built-in directional microphone that has good performance even when installed on a shelf or the like.

[Means to solve the problem]

The microphone chamber according to the present invention is a public address telephone with a built-in directional microphone, in which the area where the microphone chamber intersects with a plane parallel to the slit wall surface of the microphone chamber increases as it approaches the slit wall surface.

[Effect]

In this invention, even if an object is placed parallel to the wall surface of each slit, the surface of the placed object and the opposing side wall surface are not parallel, so the sound is not reflected infinitely and the directional microphone Since sound similar to the sound input to the front surface of the diaphragm is input to the rear surface of the diaphragm, deterioration of the directivity of the directional microphone due to objects can be reduced.

〔Example〕

FIGS. 1a and 1b show an embodiment of the present invention, in which a perspective view and a partial cross-sectional view of the mounting structure of a microphone chamber in a loudspeaker telephone are shown, and FIG. 2 shows a support bottom plate of the microphone shown in FIG. Perspective view, Figure 3 a, b, c
2 shows a plan view, a front view, and a side view of the support bottom plate portion of FIG. 2. FIG. In these figures, 12 is the inclined wall of the microphone room, and the others are as shown in Figures 14a and b.
This is the same as shown in .

In the microphone chamber of the present invention, because of the inclined wall 12, the parallel surfaces between the slit wall 4 and the side wall 11, the slit wall 5 and the side wall 9, and the slit wall 6 and the side wall 10 are reduced compared to those in FIGS. 14a and 14b. In other words, when the microphone chambers are sequentially cut along planes parallel to the slit wall, the area of the microphone chamber formed in a horn shape by the inclined wall 12, which intersects with the parallel plane, increases as it approaches the slit wall.

Therefore, even if an object (box board, shelf board, hand, etc.) is placed on a surface parallel to the slit walls 4, 5, 6, the object surface on which it is placed will be parallel to the opposing side wall surface. Because there are few surfaces, the sound is not reflected infinitely, and the rear surface of the diaphragm of a directional microphone receives sound similar to the sound that is input to the front of the diaphragm. Deterioration of directivity is reduced.

Figures 4a and 4b are a perspective view and a side view showing experimental conditions for confirming the effects of this invention, 13 is a box, and as an example, width W = 35 cm, height H = 50 cm, and depth D = 35 cm. A baking board was used. The rest is the same as shown in FIG. 1a. Speaker 3 and directional microphone 7 when the conventional microphone room shown in FIGS. 14a and 14b and the microphone room according to the present invention shown in FIGS. The amount of acoustic coupling between the two was measured. FIG. 5 shows the amount of acoustic coupling between the speaker 3 and the directional microphone 7 when the distance L between the box 13 and the loudspeaker telephone shown in FIG. 4b is changed. The measured dimensions of the base set portion of the loudspeaker telephone were approximately 16 x 23 x 6 cm (width x depth x height).

In FIG. 5, the solid line represents the microphone chamber according to the present invention, and the dotted line represents the conventional microphone chamber.
As you can see from this diagram, the microphone room of this invention is
Acoustic coupling can be reduced by approximately 1 to 4 dB compared to conventional microphone rooms.

Figures 6, 8, and 10 (corresponding to Figure 2) show the present invention when the slit wall is only on the front side, respectively.
FIG. 7 is a perspective view showing an example when applied to the front, side, and flat surfaces;
A front view, a top view, and a side view are shown in Figures a to c, Figures 9 a to c, and Figures 11 a to c. In each figure, the oblique wall 12 is indicated by a dotted line. In the examples shown in Figures 6 and 8, even if the loudspeaker telephone is installed on a shelf or the like, the external object surface and the opposing side wall surface are not parallel, so the same example as in Figure 10 (Fig. 2) is used. effective.

FIGS. 12 and 13 are sectional views of main parts showing still another embodiment of the present invention, and 14 is an uneven portion. In the embodiment shown in FIG. 12, side walls 9 and 1 of the microphone chamber are
0 and 11, in the embodiment shown in FIG. 13, the surfaces of the side walls 9, 10, 11 of the microphone chamber and the inclined wall 12 of the microphone chamber are in the shape of uneven portions 14, so that the surfaces parallel to the slit walls 4, 5, 6 are Even if an object (box board, shelf board, hand, etc.) is placed on a surface, there are few surfaces that are parallel to the object surface and the opposing side wall surface, so the sound is unlikely to be reflected infinitely. Since the rear surface of the diaphragm of the directional microphone 7 receives sound similar to the sound input to the front surface of the diaphragm, deterioration of the directivity of the directional microphone due to objects is reduced.

The directional microphone 7 is a free sound field (directional microphone 7
The diaphragm is designed so that the directivity becomes the sharpest when the same direct sound is input from the front and rear sides of the diaphragm. For this reason, if the vicinity of the directional microphone 7 is surrounded by side walls, the directivity will deteriorate due to the influence of reflection from the side walls. In particular, when the directional microphone 7 is surrounded by mutually parallel side walls,
Noise Countermeasures Handbook (published by Gihodo) Volume 2
As shown in 3.2.1.c, the sound is reflected infinitely and the synthesized sound of these reflected sounds is input to the rear surface of the diaphragm of the directional microphone 7, so the input sound on the front and rear surfaces of the diaphragm is Since the characteristics of the two are greatly different, the directional characteristics are significantly deteriorated. However, by applying the present invention, it is possible to eliminate the situation in which the directional microphone 7 is surrounded by parallel walls, so that the directional characteristics are improved.

In the above embodiment, by inserting the inclined wall 12 into the microphone chamber, the area where the microphone chamber intersects with a plane parallel to the slit wall surface increases as it approaches the slit wall surface. Of course, the microphone chamber may be configured in the above shape from the beginning without relying on the above configuration.

〔Effect of the invention〕

As explained above, this invention is configured so that the area where the microphone chamber intersects with a plane parallel to the slit wall increases as it approaches the slit wall, so that the microphone chamber is surrounded by objects having walls parallel to the slit surface. Even if the side wall surface inside the microphone chamber is not parallel to the wall surface of the object, the sound will be reflected infinitely within the microphone chamber, and the directional characteristics of the microphone will not be significantly degraded. For this reason, the present invention is applicable to loudspeaker telephones that are expected to be installed under various conditions such as on a desk, inside a shelf, or next to a wall.
It is effective in microphone rooms for tape recorders, radio cassettes, etc., and handheld vocal microphones.

Furthermore, as shown in Figs. 2, 12, and 13, this invention can be realized by only partially changing the shape of the microphone support bottom plate and the side wall surface, and no new parts are required. It has the advantage of being excellent in terms of performance and economy.

[Brief explanation of the drawing]

1A and 1B are a perspective view and a partial sectional view of a mounting structure of a microphone chamber in a loudspeaker telephone according to an embodiment of the present invention, and FIG. 3 a to c are a plan view, a front view, and a side view of the support bottom plate portion in FIG. 2, FIGS. 4 a and b are a perspective view and a side view showing the experimental conditions, and FIG. Figure, Figure 6, Figure 8
10 are perspective views showing embodiments in which the present invention is applied when the slit wall is only on the front, when the slit wall is on the front and the side, and when the slit wall is on the front, the side and a plane, respectively, and FIGS. 7a to 7c are , Figures 9a-c, Figures 11a-
Fig. 3c shows a front view, a top view, and a side view of each.
12 and 13 are sectional views of main parts showing still another embodiment of the present invention, and FIGS. 14a and 14b are perspective views and partial sectional views showing the mounting structure of a microphone chamber in a conventional loudspeaker telephone. 15 is a perspective view of the support bottom plate portion of FIG. 14. In the figure, 1 is the handset, 2 is the base set,
3 is a speaker, 4, 5, and 6 are slit walls, 7 is a directional microphone, 8 is a supporting bottom plate, 9, 10, and 11 are side walls, 12 is an inclined wall, 13 is a box, and 14 is an uneven portion.

Claims (1)

[Scope of Claims] 1. A loudspeaker telephone with a built-in directional microphone, the microphone chamber being surrounded by a slit wall provided with a hole penetrating the microphone chamber and the outside of the microphone chamber, and a side wall without the hole,
A microphone chamber characterized in that an area where a plane parallel to the slit wall surface intersects with the microphone chamber increases as it approaches the slit wall surface. 2. Claim 1 characterized in that at least a part of the slit wall or the side wall has an uneven shape.
Microphone room as described in section.