JP5941709B2 - Acoustic characteristic measuring apparatus and measuring method - Google Patents

Description

  The present invention relates to a measuring apparatus and a measuring method for measuring acoustic characteristics inside a hollow structure.

  As a method of measuring the acoustic characteristics inside the hollow structure, a sound generator such as a speaker is arranged inside the structure, and the sound emitted from the sound generator such as the speaker is also arranged inside the structure. It is preferable to receive the sound with a sound receiving device such as the sound characteristic in the structure body directly without any obstacle on the way. However, when the space inside the structure is smaller than the speaker, the speaker cannot be installed inside the structure, and such a measurement method cannot be adopted. For example, a speaker that generates a relatively low frequency sound is structurally large. However, when measuring acoustic characteristics using the speaker, it is difficult to install the speaker inside the structure.

Therefore, a method is conceivable in which sound is emitted from a speaker arranged outside the structure into the structure and received by a microphone inside the structure.
In addition, in order to identify the acoustic characteristics of a piping system or a container, a method of giving an impulse-like flow fluctuation inside the piping to be identified has been developed (see Patent Document 1).

JP-A-6-66627

However, when sound is emitted from the outside of the structure, the sound attenuation by the structure itself is large, so that it is difficult to receive sound accurately with the internal microphone. Increasing the sound from the speaker taking this attenuation into account is not preferable because the efficiency deteriorates and noise problems occur.
Further, in the technique described in Patent Document 1, an impulse-like flow rate change is caused by using compressed gas or the like, but this does not solve the acoustic characteristic measurement method using a speaker and a microphone. There is a problem that the measurement target is limited.

  The present invention has been made to solve such problems, and an object of the present invention is to provide an apparatus capable of efficiently measuring the acoustic characteristics of a structure with a simple configuration. .

In order to achieve the above-described object, in the acoustic characteristic measuring apparatus according to claim 1, the structure is hollow and has a through-hole that communicates the inside and the outside, and the through-hole is closed. a film member attached to an outer surface of said structure, and a speaker for supplying the sound within said structure from said through hole comprises a large sound generating surface than the through-hole, and said membrane member and the speaker A sound collecting member provided therebetween, a sound receiving means provided inside the structure for receiving the sound supplied from the sound generating means, and a characteristic of the sound received by the sound receiving means And the sound collecting member has a shape that is reduced in a funnel shape from the periphery of the sound generation surface of the speaker to the periphery of the inlet of the through hole, and the large opening of the sound collection member has the It is in contact with the periphery of the sound generating surface of the speaker Both the small opening of said population sound member is characterized that you have contacted through the membrane member and the through hole entrance periphery.

In the measuring apparatus of the acoustic properties of 請 Motomeko 2 Oite to claim 1, wherein the film member is characterized in that a polyimide tape.

In the method for measuring acoustic characteristics according to claim 3 , a membrane member is attached to the outer surface of a structure that is hollow and has a through-hole communicating between the inside and the outside so as to close the through-hole. A speaker having a sound generation surface larger than the through-hole is disposed outside the body, and a large opening is formed between the speaker and the membrane member so that a large opening is formed in the speaker. A sound collecting member that is in contact with the peripheral edge of the surface and whose small opening is in contact with the peripheral edge of the through hole entrance via the membrane member is disposed, and the through hole is formed by the speaker via the sound collecting member and the membrane member. supplying sound inside the structure from, the received sound by sound receiving means provided in the interior of the structure is characterized by analyzing by the acoustic analysis means a characteristic of the received sound and sound.

According to the acoustic characteristic measuring device according to the first aspect of the present invention and the acoustic characteristic measuring method according to the third aspect of the present invention, the through hole is formed in the hollow structure, and the through hole is closed with the membrane member. In addition, sound is supplied from the outside to the inside of the structure through the membrane member. The supplied sound is received by sound receiving means provided inside the structure, and analyzed by acoustic analysis means.
Thus, by closing the through hole for supplying sound from the outside with the membrane member, it is possible to minimize the change in the acoustic characteristics of the structure due to the through hole being formed. Further, since the membrane member is thin and the attenuation of sound is small, measurement can be performed even with a small sound, and measurement can be performed efficiently without noise.

Further, since it can place the speakers in the structure outside the measurement it can be easily performed using the sound of low frequency structure of a loudspeaker increases.
Furthermore, according to the acoustic characteristic measuring apparatus of the first aspect , by using the sound collecting member corresponding to the shape of the through hole and the speaker , the sound of the speaker can be more efficiently transmitted to the inside of the structure.

According to claim 2 , since the polyimide tape is thin and has low stretchability and can be attached to the structure, it can be attached as a membrane member, so that it is easy to mount and realizes efficient measurement with little attenuation. can do.

It is a schematic block diagram of the measuring apparatus of the acoustic characteristic which concerns on one Embodiment of this invention. It is the table | surface which showed ratio with the measured value and theoretical value of the resonant frequency when the measurement apparatus of the acoustic characteristic which concerns on one Embodiment of this invention is used, and when there is no thin film tape. It is a schematic block diagram of the measuring apparatus of the acoustic characteristic which concerns on the modification of this invention.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
Referring to FIG. 1, there is shown a schematic configuration diagram of an acoustic characteristic measuring apparatus according to an embodiment of the present invention.
FIG. 1 shows a bottomed cylindrical structure 1 as an acoustic characteristic measurement target in the present embodiment. The structure 1 may be a hollow structure, and specifically includes a rocket motor, an automobile muffler, a duct, and the like.

Three microphones 2, 2, 2 (sound receiving means) are provided on the outer periphery of the structure 1 in the longitudinal direction. Each microphone 2 is provided so as to penetrate the outer peripheral surface of the structure 1, and the sound receiving portion 2 a at the tip faces the inside of the structure 1.
In addition, a through hole 1 a is formed in the center of one end face of the structure 1. The through hole 1a is a circular hole having a diameter of about 10 mm, for example.

Further, a thin film tape 4 (film member) is attached to the one end face so as to close the through hole 1a. The thin film tape 4 is a film member having a thickness that is at least thinner than the outer shell of the structural body 1 and having low stretchability. For example, a polyimide tape is preferable.
A sound collector 6 (sound collecting member) is attached to one end face of the structure 1 via a thin film tape 4. The sound collector 6 has a large opening 6a with one large opening and a small opening 6b with the other opening small, and has a shape contracted in a funnel shape from the one to the other. The small opening 6b has substantially the same diameter as the through hole 1a, is arranged coaxially with the through hole 1a, and is in contact with the thin film tape 4. The large opening 6a of the sound collector 6 is provided with a speaker 8 having a sound generation surface 8a having substantially the same diameter as the large opening 6a. The speaker 8 emits a predetermined sound for measuring acoustic characteristics from the sound generation surface 8a.

The speaker 8 and each microphone 2 are electrically connected to an acoustic measuring instrument 10 (acoustic analysis means). The acoustic measuring instrument 10 controls the speaker 8 so as to emit a predetermined sound by adjusting the frequency or sound pressure according to the measurement, and receives and analyzes the sound received by each microphone 2.
In the acoustic characteristic measuring apparatus configured as described above, a method for measuring the acoustic characteristic of the structure 1 will be described below.

  In the acoustic measuring instrument 10, one or a plurality of predetermined sounds are set in advance, and a predetermined sound corresponding to the measurement is selected at the time of measurement, and the selected sound is controlled to be emitted from the speaker 8. The sound emitted from the speaker 8 is collected from the large opening 6a of the sound collector 6 toward the small opening 6b, and is transmitted from the small opening 6b to the through hole 1a through the thin film tape 4. The sound is supplied into the structure 1 from the through-hole 1a.

Each microphone 2 receives the sound supplied to the inside of the structure 1 at a position where it is arranged, and sends the received sound information to the acoustic measuring instrument 10. The acoustic measuring instrument 10 analyzes the acoustic characteristics at each position of the structure 1 by analyzing information received from each microphone 2.
Referring now to FIG. 2, there is shown a table showing the ratio between the measured value and the theoretical value of the resonance frequency when the acoustic characteristic measuring device according to one embodiment of the present invention is used and when there is no thin film tape. ing. In FIG. 2, the sound having the same characteristics is supplied to the same structure 1 and the frequency of the sound received by the microphone 2 closest to the through hole 1a shown in FIG. The frequency of the sound received by is shown as a secondary value, and the frequency of the sound received by the microphone 2 farthest from the through hole 1a is shown as a tertiary value.

  As shown in FIG. 2, even if the object is the same structure 1, when measurement is performed without blocking the through-hole 1a, the ratio between the measured value and the theoretical value received by each microphone 2 is It becomes a low value, and the measured value and the theoretical value are separated. In particular, it can be seen that the actually measured value is far from the theoretical value as the sound is received by the microphone 2 close to the speaker 8. On the other hand, in the case of the present embodiment in which the through-hole 1 a is closed by the thin film tape 4, the ratio between the actual measurement value received by each microphone 2 and the theoretical value is close to 1 and It can be seen that the actual acoustic characteristics can be measured.

  As described above, the speaker 8 is outside the structure 1, and the sound emitted from the speaker 8 is transmitted to the inside of the structure 1 through the through hole 1 a, but the through hole 1 a is closed with the thin film tape 4. Thus, the change in the acoustic characteristics of the structure 1 due to the through-hole 1a being drilled can be minimized. Further, since the thin film tape 4 is thin and the sound attenuation is small, measurement can be performed even with a small sound, and the measurement can be performed efficiently without noise. In particular, by using a thin and low-stretch polyimide tape, it is easy to mount and efficient measurement with little attenuation can be realized.

Since the speaker 8 can be disposed outside the structure 1, measurement using low-frequency sound that increases the structure of the speaker 8 can be easily performed. In addition, by using the sound collector 6 corresponding to the shape of the through hole 1 a and the speaker 8, the sound of the speaker 8 can be transmitted to the inside of the structure 1 more efficiently.
From the above, according to the measurement apparatus and measurement method for acoustic characteristics according to the present invention, acoustic characteristics can be efficiently measured with a simple configuration even for a structure having a small internal space.

Although the description of the embodiments of the acoustic characteristic measuring device and the measuring method according to the present invention has been finished above, the embodiments are not limited to the above embodiments.
For example, in the above-described embodiment, the through hole 1a is formed in one end face of the structure 1, and the speaker 8 is arranged substantially coaxially with the structure 1. However, the position of the through hole 1a and the speaker 8 are arranged. The position of is not limited to this. For example, as in the modification shown in FIG. 3, a through-hole 1a ′ is formed on one side of the outer peripheral surface of the structure 1 ′, and a thin film tape 4 ′ is attached to the outer peripheral surface. A configuration may be adopted in which the sound collector 6 'and the speaker 8' are arranged perpendicular to the axial direction of '.

  Moreover, in the said embodiment, although the structure 1 has comprised the bottomed cylinder shape, it is a cylindrical structure body by which the end surface was open | released, or the diameter is not constant but the diameter is expanded from one side to the other side. The present invention can be applied to a reduced shape or a polygon such as a square whose cross section is not circular.

1, 1 'structure 1a, 1a' Through-hole 2 Microphone (sound receiving means)
4 Thin film tape (membrane member)
6 Sound collector (sound collecting member)
8 speakers
10 acoustic measuring instrument (acoustic analysis means)

Claims (3)

A structure that is hollow and has a through-hole communicating between the inside and the outside;
A membrane member attached to the outer surface of the structure so as to close the through hole;
A speaker for supplying the sound within said structure from said through hole comprises a large sound generating surface than the through-hole,
A sound collecting member provided between the speaker and the membrane member;
A sound receiving means provided inside the structure for receiving a sound supplied from the speaker ;
Acoustic analysis means for analyzing the characteristics of the sound received by the sound receiving means;
Equipped with a,
The sound collecting member has a shape that is reduced in a funnel shape from the periphery of the sound generation surface of the speaker to the periphery of the through-hole entrance, and the large opening of the sound collection member has a periphery of the sound generation surface of the speaker. measurement apparatus acoustic characteristic small opening portion of said population sound member characterized that you have contacted through the membrane member and the through hole entrance periphery with contacts. Said membrane member, the measuring device of the acoustic characteristics of claim 1 Symbol mounting characterized in that it is a polyimide tape. A membrane member is attached to the outer surface of the structure that is hollow and has a through-hole that communicates the inside and the outside so as to close the through-hole.
A speaker having a sound generation surface larger than the through hole is disposed outside the structure , and a funnel-shaped large opening is formed between the speaker and the membrane member. A sound collecting member that is in contact with the peripheral edge of the sound generating surface and whose small opening is in contact with the peripheral edge of the through-hole inlet and the membrane member is disposed.
Sound is supplied from the through hole to the inside of the structure through the sound collecting member and the film member by the speaker ,
And sound reception by sound receiving means provided in the interior of said structure,
A method for measuring acoustic characteristics, characterized in that the characteristics of the received sound are analyzed by acoustic analysis means.

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