JP5817191B2 - Method for measuring acoustic characteristics of acoustic material and apparatus for measuring acoustic characteristics of acoustic material - Google Patents

Description

  The present invention relates to an acoustic material acoustic property measuring method and an acoustic material acoustic property measuring apparatus.

The following methods are known as methods for measuring acoustic characteristics such as reflection characteristics and transmission characteristics of acoustic materials used in water (see Non-Patent Document 1).
As shown in FIG. 1, a specimen 2 whose acoustic characteristics are to be measured, a transmitter T, and a receiver R are placed in water.
By supplying a driving signal to the transmitter T, a first sound wave (direct wave) is transmitted from the transmitter T toward the specimen 2, and the first sound wave is reflected by the specimen 2. The received sound wave (reflected wave) is received by the receiver R to detect the reflected wave detection signal.
An acoustic characteristic is calculated based on the sound pressure level of the second sound wave calculated from the reflected wave detection signal.

Ocean Acoustics Fundamentals and Applications Ocean Acoustics Society Chapter 12 Underwater Acoustic Measurement (p147-p148)

However, the conventional method shown in FIG. 1 has the following problems when the first sound wave is transmitted with the incident angle inclined with respect to the specimen 2 as shown in FIG.
The angle formed by the traveling direction of the direct wave transmitted from the transmitter T toward the specimen 2 and the normal of the surface of the specimen 2 is defined as the incident angle θ of the direct wave.
The distance between the transmitter T and the receiver R is a first distance, and the distance of the path from the transmitter T → the specimen 2 → the receiver R is a second distance.
In this case, if a difference between the first distance and the second distance is ensured to some extent, a time difference Δt12 between the first sound wave and the second sound wave detected by the receiver R can be ensured. A sound wave and a second sound wave can be identified and measured.
However, as the incident angle θ increases, for example, when the incident angle θ exceeds 30 degrees, the time difference Δt12 becomes too short, and it becomes difficult to distinguish and measure the first sound wave and the second sound wave. .
For this reason, in the conventional method, it is difficult to measure the acoustic characteristics of the specimen at an incident angle θ exceeding 30 degrees, and the incident angle of sound waves to the specimen is restricted.
The present invention has been made in view of the circumstances as described above, and an object of the present invention is to provide a method for measuring acoustic characteristics of an acoustic material, which is advantageous in eliminating the limitation on the incident angle of a sound wave to a specimen, and the acoustic characteristics of the acoustic material. The object is to provide a characteristic measuring apparatus.

In order to achieve the above-mentioned object, the present invention provides a test signal whose acoustic characteristics are to be measured, a transmitter, and a receiver in water and supplies a driving signal to the transmitter. A first sound wave is transmitted from the wave generator toward the specimen, and the second sound wave, which is a reflected wave reflected by the specimen, is transmitted between the specimen and the wave transmitter. An acoustic wave that is received by the receiver disposed between them, detects a reflected wave detection signal, and calculates the acoustic characteristics based on the sound pressure level of the second sound wave calculated from the reflected wave detection signal A method for measuring acoustic characteristics of a material, wherein the transmitters are directed to the same direction and n pieces (n is a distance n) on a straight line extending in a direction crossing the directed direction. Integers of 2 or more) are arranged side by side, and the n transmitters are defined as first, second,... N transmitters. In this case, the drive signal is generated so that the phase of the first sound wave transmitted from the first, second,... 2. An incident angle formed by the traveling direction of the equiphase surface formed by the n first sound waves transmitted from the nth transmitter and the normal of the surface of the specimen is 0 degree. The acoustic characteristic at an arbitrary incident angle is calculated so that the angle is larger than the angle.
The present invention is placed in water, the first sound wave by a drive signal is supplied and wave transmitter for transmitting toward a specimen to be measured acoustic characteristics, feed and the specimen of the water The second sound wave, which is disposed between the waver and the first sound wave is reflected by the specimen, is received, and a reflected wave detection signal corresponding to the second sound wave is generated. An acoustic characteristic of the specimen is calculated based on a sound pressure level of the second sound wave calculated from the wave receiver, the driving means for supplying the driving signal to the transmitter, and the reflected wave detection signal. An acoustic characteristic measuring device comprising: an acoustic characteristic calculating means; wherein the transmitter directs in the same direction and has an equal interval d on a straight line extending in a direction crossing the directed direction. And n (n is an integer of 2 or more) arranged side by side, and the driving means includes the n When the transmitter is a first, second,... Nth transmitter, the phase of the first sound wave transmitted from the first, second,. The drive signal is generated so as to be shifted by a phase difference φ, and the equiphase surface is formed by the n first sound waves transmitted from the first, second,... N transmitters. The incident angle formed by the traveling direction of the specimen and the normal line of the surface of the specimen is an angle larger than 0 degrees, and the acoustic characteristics at an arbitrary incident angle are calculated .

  According to the present invention, the first to n-th transmitters are arranged in the same direction and arranged side by side at equal intervals d on the straight line, and the first to n-th transmitters transmit the waves. The drive signal is generated so that the phase of the first sound wave to be shifted by the phase difference φ, and the equal phase formed by the n first sound waves transmitted from the first to n-th transmitters The incident angle θ formed by the traveling direction of the surface and the normal line of the surface of the specimen was set to be larger than 0 degree. Therefore, it is possible to measure the acoustic characteristics of the specimen at an incident angle larger than 0 degrees, which is difficult with the conventional method, which is advantageous in eliminating the restriction on the incident angle of the sound wave to the specimen.

It is explanatory drawing of the acoustic characteristic measurement method of the conventional acoustic material. It is the figure which showed the measured value of the sound pressure level P of the 1st, 2nd, 3rd sound wave W1, W2, W3 detected by the receiver R. It is explanatory drawing at the time of setting incident angle (theta) with respect to the surface of the test body 2 of the 1st sound wave W1 transmitted from the transmitter T to an angle larger than 0 degree | times. It is a diagram which shows the relationship between incident angle (theta) and time difference (DELTA) t. It is explanatory drawing in the case of transmitting the diagonally sound wave with the dipole-shaped hydrophone model which consists of two transmitter T1, T2. It is explanatory drawing in the case of transmitting a sound wave with the incident angle (theta) to the specimen 2 by 1st-4th transmitter T1-T4. It is a block diagram which shows the structure of the acoustic characteristic measuring apparatus in this Embodiment. (A) is a diagram showing a simulation procedure, (B) is an explanatory diagram of a sound field, (C) is a diagram showing a phase change in the width direction of the specimen 2, and (D) is a transmitter (hydrophone). It is a figure which shows the simulation result of phase difference (phi) among them, wavelength (lambda) of a sound wave, and incident angle (theta). It is a figure which shows the simulation result of phase difference (phi) between wave transmitters (hydrophone) in case two transmitters, the wavelength (lambda) of sound wave, and incident angle (theta). It is a figure which shows the simulation result of phase difference (phi) between the wave transmitters (hydrophone), the wavelength (lambda), and incident angle (theta) between three wave transmitters. It is a figure which shows the simulation result of phase difference (phi) between wave transmitters (hydrophone), the wavelength (lambda) of sound waves, and incident angle (theta) in the case of four transmitters. It is a figure which shows the simulation result of phase difference (phi) between wave transmitters (hydrophone), wavelength (lambda) of sound waves, and incident angle (theta) in the case of five transmitters.

Next, the acoustic characteristic measuring device for acoustic material according to the embodiment of the present invention will be described together with the acoustic characteristic measuring method for acoustic material, and a conventional method as a premise of the present invention will be described.
FIG. 1 is an explanatory diagram of a method for measuring acoustic characteristics of a conventional acoustic material.
As shown in FIG. 1, a specimen 2 whose acoustic characteristics are to be measured, a transmitter T, and a receiver R are suspended and placed in water contained in a water tank 1. In this case, the distance from the transmitter T increases in the order of the receiver R, the specimen 2, and the wall surface of the water tank 1.
By supplying a drive signal to the transmitter T, the first sound wave W1 is transmitted from the transmitter T toward the specimen 2.
In this case, the incident angle θ that the traveling direction of the first sound wave W1 is normal to the surface of the specimen 2 is 0 degree, that is, the first sound wave W1 is incident in the direction perpendicular to the surface of the specimen 2. To do.
The first sound wave W <b> 1 reaches the receiver R, the specimen 2, and the wall surface of the water tank 1 in this order.
A part of the first sound wave W1 (direct wave) that has reached the specimen 2 is reflected by the specimen 2 and travels toward the receiver R as a second sound wave (reflected wave), and the remaining first waves The sound wave W1 passes through the specimen 2 and then is reflected by the wall surface of the water tank 1, and reaches the receiver R as the third sound wave W3.
FIG. 2 is a diagram showing measured values of the sound pressure level P of the first, second, and third sound waves W1, W2, and W3 detected by the receiver R.
As described above, the second sound wave W2 reflected by the specimen 2 is received by the receiver R to detect the second detection signal, and the second detection signal calculated from the second detection signal is used. The reflection coefficient as the acoustic characteristic is obtained from the sound pressure level P of the second sound wave W2.
More specifically, the sound pressure level of the second sound wave W2 is obtained when the reflected sound pressure obtained with a complete reflector made of a sufficiently thick iron plate or the like is used as a reference, and the complete reflector is replaced with the specimen 2. The reflection coefficient is obtained from P.

FIG. 3 is an explanatory diagram when the incident angle θ of the first sound wave W1 transmitted from the transmitter T with respect to the surface of the specimen 2 is set to an angle larger than 0 degrees.
Hereinafter, a path (direct wave path) from the transmitter T to the first sound wave W1 transmitted directly to the receiver R and a first sound wave W1 transmitted from the transmitter T are When the receiver R detects the path (reflected wave path) from the specimen 2 to the receiver R as the second sound wave W2, the two sound waves W1 and W2 are temporally detected. The conditions for enabling separation are illustrated.
Propagation distance of reflected wave: distance connecting transmitter T, point O on specimen 2 and receiver R TOR = L + D (1)
Here, L is a distance connecting the transmitter T and the point O on the specimen 2, and D is a distance connecting the point O on the specimen 2 and the receiver R.
Propagation distance of direct wave: distance TR connecting the transmitter T and the receiver R = (L ² + D ² −2LD · cos (2θ)) ^1/2 (2)
Time difference between direct wave and reflected wave: Δt = (TOR−TR) / c (3)
Transmission time when the frequency is f and the number of peaks is N: N / f (4)
The conditions under which direct waves and reflected waves can be separated are as follows.
Δt = (TOR−TR) / c> N / f (5)
Where c is the speed of sound in water = 1500 m / s
FIG. 4 is a diagram showing the relationship between the incident angle θ and the time difference Δt.
In FIG. 4, L = 500 mm, D = 350 mm, f = 20 kHz, and N = 5.
In this case, if the transmission time N / f = 0.25 ms, it is difficult to temporally separate the two sound waves W1 and W2 if the time difference Δt is 0.25 ms or less.
Therefore, from FIG. 4, the incident angle θ with a time difference Δt = 0.25 ms or less is a region of about 33 degrees or more.
Thus, it can be seen that the conventional method described above has a limitation on the incident angle θ of the sound wave with respect to the specimen 2.

Therefore, the present invention has been made in order to eliminate such a restriction on the incident angle θ of the sound wave with respect to the specimen 2, and in the same manner as the sonar phasing process, a plurality of transmitters are provided with phase differences. By transmitting and receiving waves, the equiphase surface is incident on the surface of the specimen 2 from an oblique direction. In other words, the acoustic characteristics of the acoustic material can be measured in a range where the incident angle θ is larger than 0 degrees. It is a thing.
Here, a case will be described in which a plurality of transmitters transmit acoustic waves that are skewed.
As shown in FIG. 5, the case of transmitting with a dipole-shaped hydrophone model including two transmitters T1 and T2 will be described.
The two transmitters T1 and T2 are arranged on the straight line L1 with a distance d. More specifically, the two transmitters T1 and T2 are arranged at an equal interval d on a straight line L1 that is directed in the same direction and that extends in a direction intersecting the directed direction.
Here, a case where a sound wave is incident at an incident angle θ on a straight line parallel to the straight line L1 (in other words, a case where the angle formed by the traveling direction of the sound wave with respect to the straight line L2 orthogonal to the straight line L1 is θ) is considered. .
The sound waves transmitted by the two transmitters T1 and T2 are S ₁ and S ₂ respectively, the position of the sound wave S2 having the same phase as the sound wave S1 (the position of the equiphase surface) is the position H, and the wavelength of the sound wave is λ To do.
In this case, Expression (10) is established.
S ₂ H = dsin θ (10)
The phase difference φ between the sound waves S ₁ and S ₂ transmitted by the two transmitters T1 and T2 is expressed by Expression (11).
φ = (2πd / λ) sin θ (11)
Then, the sound pressure of the sound wave transmitted by the two transmitters T1 and T2 is obtained by vector synthesis of the transmitted sound pressures p ₁ and p ₂ of the _two transmitters T1 and T2, as shown in Expression (12). Become.
p ₁ + p ₂ = 2p ₁ cos (φ / 2) (12)
The case where the two transmitters T1 and T2 transmit sound waves in the traveling direction having an angle θ with respect to the straight line L2 has been described above, but the two transmitters T1 and T2 are replaced with two receivers. Then, it is possible to receive a sound wave incident at an incident angle θ with respect to a straight line parallel to the straight line L2.

FIG. 6 is an explanatory diagram when a sound wave is transmitted to the specimen 2 at an incident angle θ by the first to fourth transmitters T1 to T4.
Four transmitters T1 to T4 are arranged at equal intervals on the straight line L1.
More specifically, the first to fourth transmitters T1 to T4 are arranged at an equal interval d on a straight line L1 that is directed in the same direction and that extends in a direction intersecting the directed direction. ing.
The specimen 2 has a plate shape, for example, and when the normal of the surface of the specimen 2 is L2, the specimen 2 is arranged so that the straight line L1 and the normal L2 are orthogonal to each other.
Drive signals are supplied to the first to fourth transmitters T1 to T4 so that the phases of the sound waves transmitted from the first to fourth transmitters T1 to T4 are shifted by a phase difference φ.
Then, the incident angle θ formed by the traveling direction of the equiphase surface P formed by the four sound waves transmitted from the first to fourth transmitters T1 to T4 and the normal of the surface of the specimen 2 is The angle can be greater than 0 degrees.

Next, a specific configuration of the acoustic characteristic measuring device will be described.
FIG. 7 is a block diagram showing the configuration of the acoustic characteristic measuring apparatus according to the present embodiment.
The acoustic characteristic measuring apparatus 10 includes a water tank 1, first to fourth transmitters T1 to T4, a receiver R, an oscillator 12, a power amplifier 14, first to fourth phase shifters 16A to 16D, and a preamplifier 18. , An attenuator 20, a switching device 22, a measuring amplifier 24, a filter 26, an oscilloscope 28, a digital oscilloscope 30, a personal computer 32, and the like.

The water tank 1 contains water.
1st-4th transmitter T1-T4 is arrange | positioned in the water of the water tank 1, and transmits a 1st sound wave toward the specimen 2 which should measure an acoustic characteristic by supplying a drive signal. Is.
More specifically, the first to fourth transmitters T1 to T4 are arranged at an equal interval d on a straight line L1 that is directed in the same direction and that extends in a direction intersecting the directed direction. ing.
In the present embodiment, the specimen 2 has a plate shape and is disposed so that the normal line L2 of the surface thereof is orthogonal to the straight line L1.

The receiver R is disposed in the water of the water tank 1, receives a second sound wave that is a reflected wave reflected by the specimen 2, and detects a reflected wave detection signal corresponding to the second sound wave. Is generated.
In this Embodiment, the receiver R is arrange | positioned in the position which can receive the reflected wave from the specimen 2 between the 1st-4th transmitter T1-T4 and the specimen 2. FIG. .

  The oscillator 12 generates a drive signal to be supplied to the first to fourth transmitters T1 to T4, and is configured to be able to adjust the amplitude, wave number (pulse number), wavelength, and the like of the drive signal.

  The power amplifier 14 amplifies the drive signal supplied from the oscillator, and is configured such that the amplification factor can be adjusted.

The first to fourth phase shifters 16A shift the drive signal supplied from the power amplifier 14 by a preset phase difference and supply it to the first to fourth transmitters T1 to T4. .
In the present embodiment, the phase difference φ shifted by the first to fourth phase shifters 16A is as follows.
First transmitter: 0
Second transmitter: φ
Third transmitter: 2φ
Fourth transmitter: 3φ
Therefore, with reference to the phase of the first transmitter T1, the second, third, and fourth transmitters T2, T3, and T4 have a phase difference φ, a phase difference 2φ, and a phase difference 3φ, respectively. Sound waves will be transmitted.

  The preamplifier 18 amplifies the reflected wave detection signal supplied from the receiver R.

  The attenuator 20 attenuates the drive signal supplied from the power amplifier 14 to the first to fourth phase shifters 16A by a predetermined attenuation amount.

  The switch 22 selects the reflected wave detection signal supplied from the preamplifier 18 and the drive signal supplied from the power amplifier 14 to the first to fourth phase shifters 16A and supplies the selected signal to the measuring amplifier 24. It is.

  The measuring amplifier 24 amplifies either the reflected wave detection signal supplied via the switch 22 or the drive signal and outputs the amplified signal as an output signal.

  The filter 26 removes unnecessary signal components from the output signal supplied from the measuring amplifier 24, particularly from the reflected wave detection signal.

  The oscilloscope 28 receives the drive signal supplied from the oscillator 12 as a trigger signal and monitors the waveform of the reflected wave detection signal that has passed through the filter 26.

  The digital oscilloscope 30 receives the drive signal supplied from the oscillator 12 as a trigger, accumulates the reflected wave detection signal that has passed through the filter 26 as data, and supplies the reflected wave detection signal data to the personal computer 32. .

The personal computer 32 is installed with a dedicated measurement program. By executing this measurement program, the sound pressure level of the second sound wave is calculated from the data of the reflected wave detection signal supplied from the digital oscilloscope 30, and Based on the calculated sound pressure level of the second sound wave, the acoustic characteristics of the specimen 2 are calculated.
The personal computer 32 also controls operations of the oscillator 12, the filter 26, and the digital oscilloscope 30.
In this embodiment, the oscillator 12, the power amplifier 14, and the first to fourth phase shifters constitute drive means as claimed in the claims, and the personal computer 32 performs the acoustics as claimed in the claims. Characteristic calculating means is configured.

When the switch 22 is switched to the attenuator 20 side, the drive signal supplied from the power amplifier 14 to the first to fourth phase shifters 16A is directly supplied to the measuring amplifier 24. By doing in this way, the reference level of a drive signal can be obtained by directly measuring the drive signal which is not influenced by the situation in the aquarium 1 (underwater).
When the amplification factor (output power) of the power amplifier 14 is changed, the detection signal of the receiver R can be corrected based on the reference level, and the detection signal is measured more accurately. .

Next, the operation of the acoustic characteristic measuring apparatus 10 will be described.
First, the first to fourth transmitters T1 to T4, the receiver R, and the specimen 2 are suspended and installed in the water of the water tank 1.
An incident angle θ of the sound wave transmitted from the first to fourth transmitters T1 to T4 with respect to the specimen 2 is determined. The incident angle θ is a value larger than 0 degree and smaller than 90 degrees.
From the aforementioned equation (11), the phase difference φ is calculated based on the incident angle θ, the wavelength λ of the sound wave transmitted from the first to fourth transmitters T1 to T4, and the interval d.
φ = (2πd / λ) sin θ (11)
Based on the phase difference φ, the phases of the first to fourth phase shifters 16A to 16D are set.
The switch 22 is switched to the preamplifier 18 side.

The personal computer 30 gives a command for generating a drive signal to the oscillator 12. Accordingly, the drive signal is supplied from the oscillator 12 to the first to fourth wave transmitters T1 to T4 via the power amplifier 14 and the first to fourth phase shifters 16A to 16D.
As a result, as shown in FIG. 6, sound waves shifted by the phase difference φ are transmitted from the first to fourth transmitters T1 to T4, and the traveling direction of the equiphase surface P formed by these four sound waves The incident angle θ formed by the normal of the surface of the specimen 2 becomes an angle larger than 0 degrees, and therefore the first sound wave W1 (FIG. 2) having an incident angle θ larger than 0 degrees with respect to the specimen 2 is generated. It is transmitted.
In the receiver R, the reflected wave detection signal is supplied to the measuring amplifier 24 by receiving the second sound wave W2 (FIG. 2) which is a reflected wave reflected by the specimen 2 from the first sound wave W1. .

The reflected wave detection signal is accumulated in the digital oscilloscope 30 via the measuring amplifier 24 and the filter 26.
The personal computer 32 calculates the sound pressure level P2 of the second sound wave W2 based on the reflected wave detection signal data stored in the digital oscilloscope 30, and calculates the acoustic characteristics from the sound pressure level P2.
Examples of the acoustic characteristics include a reflection coefficient ER (echo reduction (reflection attenuation amount)) for evaluating a conventionally known reflection characteristic. The reflection coefficient ER indicates how much the attenuation is, and takes a positive value when it attenuates.
It is assumed that the sound pressure level P2 = P_sample in the state in which the specimen 2 is installed with respect to the sound pressure level P2 = P_ref in the reference state (in which the reference sample is installed). At this time, the reflection coefficient ER is calculated by the following equation (20).
ER = -20Log ₁₀ (P_sample / P_ref) …… (20)

As described above, according to the present embodiment, the first to fourth transmitters T1 to T4 are oriented in the same direction and arranged side by side at equal intervals d on the straight line. Drive signals are generated so that the phase of the first sound wave W1 transmitted from the fourth transmitters T1 to T4 is shifted by a phase difference φ, and the first to fourth transmitters T1 to T4 The incident angle θ formed by the traveling direction of the equiphase surface P formed by the four first sound waves W1 transmitted and the normal line of the surface of the specimen 2 is set to be larger than 0 degree. .
Therefore, it is possible to measure the acoustic characteristics of the specimen 2 at an incident angle θ exceeding 30 degrees, which is difficult with the conventional method, and eliminates the restriction of the incident angle θ on the specimen 2 of the sound wave. This is advantageous.

In the first embodiment, the case where four transmitters of the first to fourth transmitters T1 to T4 are provided is illustrated, but there are two, three, or five or more transmitters. It may be.
Hereinafter, with respect to the case where the number of transmitters is two, three, four, and five, the results of the simulation on how the phase difference φ, the wavelength λ of the sound wave, and the incident angle θ can be set. explain.

8A is a diagram showing a simulation procedure, FIG. 8B is an explanatory diagram of a sound field, FIG. 8C is a diagram showing a phase change in the width direction of the specimen 2, and FIG. 8D is a transmitter (hydrophone). FIG. 6 is a diagram illustrating simulation results of a phase difference φ, a sound wave wavelength λ, and an incident angle θ.
As shown in FIG. 8A, the frequency f (wavelength λ) of the sound wave transmitted from the transmitter, the number of transmitters, the interval d, and the phase difference φ are set (step S1).

Next, the sound field in the aquarium 1 is calculated based on the setting contents in step S1 (step S2).
The calculation result of the sound field is shown in FIG. In the figure, the X axis and the Y axis indicate two-dimensional coordinate axes set in a state in which the water tank 1 is viewed in plan, and the vertical axis indicates the sound pressure level P (dB).
In this example, the extending direction of the straight line L1 on which the transmitters are arranged matches the Y axis, and the X axis extends in a direction perpendicular to the Y axis.
As shown in FIG. 8B, the sound pressure level P of the sound wave transmitted from each of the plurality of transmitters is shown.

Next, the phase of the sound wave at a position at a certain distance from each transmitter is calculated (step S3).
In FIG. 8C, the horizontal axis (Y axis) indicates the distance in the width direction of the specimen 2 (extending direction of the straight line L1 on which the transmitters are arranged), and the vertical axis indicates the phase (degree).
Therefore, the phase corresponding to the dimension in the width direction of the specimen 2 corresponds to the incident angle θ.

Next, the relationship between the phase difference φ between the transmitters and the incident angle θ calculated in step S3 is calculated using the interval d and the frequency (wavelength λ) of the sound wave as parameters (step S4).
The result is shown in FIG. In FIG. 8D, the horizontal axis indicates the phase difference φ between the transmitters, and the vertical axis indicates the incident angle θ.
FIG. 8D shows the case where there are two transmitters, which are the same as FIG.
FIGS. 10, 11 and 12 show the cases of three, four and five transmitters, respectively.

As shown in FIG. 9, when there are two transmitters, the distance d can be set to a wavelength λ or less, but the incident angle θ is about 30 degrees or less.
As shown in FIG. 10, when there are three transmitters, the incident angle θ can be set to about 70 degrees in a range where the distance d is 3λ / 4 or less.
As shown in FIG. 11, when there are four transmitters, the incident angle θ can be set to about 70 degrees in the range where the distance d is λ / 4 to λ / 2.
As shown in FIG. 12, even when there are five transmitters, the incident angle θ can be set to about 70 degrees in the range where the distance d is in the range of λ / 4 to λ / 2.
According to such a simulation result, in order to change the incident angle θ, it is understood that at least one of the distance d or the wavelength λ may be changed.

In the present embodiment, one drive signal generated using a single oscillator 12 and a single power amplifier 14 is shifted by four phase shifts 16 using four phase shifters 16A to 16D, and four transmission signals are transmitted. It was set as the structure supplied to the wave devices T1-T4.
However, an oscillator 12 and a power amplifier 14 may be provided for each of the transmitters T1 to T4, and the phase of the drive signal of each oscillator 12 may be shifted by a phase difference φ and supplied to the four transmitters T1 to T4. . However, the configuration of the present embodiment is more advantageous in reducing the cost because only one oscillator 12 and one power amplifier 14 are required.

In the present embodiment, the transmitters T1 to T4 and the receiver R are separated, but the following modifications are also possible.
(1) Any one of the transmitters T1 to T4 is also used as the receiver R.
(2) All or two or more of the transmitters T1 to T4 are also used as the receiver R.
Even in such a modification, it is needless to say that the same effect as in the embodiment can be obtained, and the receiver is also used as the transmitter, which is advantageous in reducing the cost.
In the case of (2), since the second sound wave W2 is received by a plurality of receivers, a phase difference opposite to that at the time of transmission is given to each detected reflected wave detection signal. It is necessary to phase the second sound wave W2 detected by the above.
That is, the personal computer 32 calculates the acoustic characteristics of the specimen 2 after performing a phasing process having a phase opposite to the phase difference φ on the reflected wave detection signals generated by the plurality of receivers.

  T1 to T4... 1 to 4 transmitters, R... Receivers, 1... Water tank, 2 .. specimen, 10. 14 …… Power amplifier (drive means), 16A to 16D …… First to fourth phase shifters (drive means), 18 …… Preamplifier, 20 …… Attenuator, 22 …… Switch, 24 …… Measurement Amplifier 26... Filter 28. Oscilloscope 30. Digital oscilloscope 32. Personal computer (acoustic characteristic calculation means).

Claims (3)

Place the specimen whose acoustic characteristics are to be measured, the transmitter, and the receiver in the water,
A first sound wave is transmitted from the transmitter toward the specimen by supplying a driving signal to the transmitter;
The second sound wave, which is a reflected wave reflected by the specimen, is received by the receiver disposed between the specimen and the transmitter, and a reflected wave detection signal is received. To detect
An acoustic characteristic measurement method for an acoustic material that calculates the acoustic characteristic based on a sound pressure level of the second sound wave calculated from the reflected wave detection signal,
The transmitters are arranged in the same direction and n (n is an integer of 2 or more) arranged at equal intervals d on a straight line extending in a direction intersecting with the directed direction.
When the n transmitters are first, second,..., Nth transmitters, the first, second,... The drive signal is generated so that the phase of the sound wave is shifted by a phase difference φ,
The traveling direction of the equiphase surface formed by the n first sound waves transmitted from the first, second,..., Nth transmitters and the normal of the surface of the specimen. So that the incident angle is larger than 0 degree ,
Calculating the acoustic characteristic at any angle of incidence;
A method for measuring acoustic characteristics of an acoustic material. Setting the incident angle θ by adjusting at least one of the phase difference φ and the wavelength of the first sound wave;
The method for measuring acoustic characteristics of an acoustic material according to claim 1. A transmitter that is disposed in water and that transmits a first sound wave toward a specimen whose acoustic characteristics are to be measured by supplying a drive signal;
It arrange | positions between the said test body and transmitter in the said water , The said 1st sound wave receives the 2nd sound wave which is the reflected wave reflected by the said test body, and respond | corresponds to the said 2nd sound wave A receiver for generating a reflected wave detection signal to be transmitted;
Drive means for supplying the drive signal to the transmitter;
Acoustic characteristic calculation means for calculating an acoustic characteristic of the specimen based on a sound pressure level of the second sound wave calculated from the reflected wave detection signal;
An acoustic characteristic measuring apparatus comprising:
The transmitters are arranged in the same direction and n (n is an integer of 2 or more) arranged at equal intervals d on a straight line extending in a direction intersecting with the directed direction.
When the n transmitters are the first, second,..., Nth transmitters, the driving means is transmitted from the first, second,... Nth transmitters. Generating the drive signal so that the phase of the first sound wave is shifted by a phase difference φ,
The traveling direction of the equiphase surface formed by the n first sound waves transmitted from the first, second,..., Nth transmitters and the normal of the surface of the specimen. So that the incident angle is larger than 0 degree ,
Calculating the acoustic characteristic at any angle of incidence;
An acoustic characteristic measuring device characterized by that.

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