JP2730870B2 - Sound conversion efficiency measuring method and measuring device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an underwater sound wave receiver, and at least a part of the object to be measured which is disposed underwater, for example, a marine observation boat or an ultrasonic fish finder equipped with an underwater sounding device. Receiving the excitation force, which indicates how the vibration applied to the hull of the fishing boat affected the signal received by the underwater sound wave receiver such as the mounted underwater sounder and ultrasonic fish finder. The present invention relates to an acoustic conversion efficiency measuring method for measuring the conversion efficiency into a signal for each point on a measured object and an acoustic conversion efficiency measuring device used for implementing the method.

[0002]

2. Description of the Related Art FIG. 9 is an external view of a hull, and FIG. 10 is a schematic diagram showing a flow of vibrations propagating in a hull and sounds propagating in water. An underwater acoustic wave transmitter / receiver 2 is provided at the lower front end of the hull 1, and sound waves are transmitted from the underwater acoustic wave transmitter / receiver 2 to the water below or forward of the hull 1, and reflected by the sea floor or a school of fish. The returned sound wave is again received by the underwater sound wave transmitter / receiver 2, and this is displayed on the screen to confirm the position of the sea floor or the school of fish. Incidentally, in FIG.
The contour pattern drawn on the outer wall of the hull will be described later.

However, when an engine, a motor, etc. mounted on the hull 1 (representatively, the motor 3 is shown in FIG. 10) are operated, the hull vibrates. As shown in 10, the underwater sound wave transceiver 2 receives the sound wave via the hull itself (solid propagation), or is radiated as sound waves into the water through the outer wall of the hull, and the sound waves pass through the water (water propagation). This may cause noise and deteriorate the detection performance of the underwater acoustic wave transceiver 2. The effect is much greater for sound waves traveling underwater than for vibrations traveling through the hull itself.

[0004]

In order to improve the S / N ratio of the underwater acoustic wave receiver mounted on the hull, it is desired to take measures to prevent vibration of the hull. It is not always clear whether taking measures can reduce the noise of the underwater acoustic wave transmitter / receiver, and there is a problem in that blindly taking measures against vibrations would require enormous costs.

In order to search for a noise source that causes underwater propagation which is a major cause of noise, when each point of the hull is vibrated, it is necessary to determine how much noise the vibrating force appears in the underwater acoustic wave transceiver. represents, the excitation force, the conversion efficiency eta _t to noise was measured for each point of the hull, for example, by obtaining a contour distribution of the conversion efficiency eta _t as shown in FIG. 9, a large part of the conversion efficiency eta _t It is effective to find out. Thus we find a large part of the conversion efficiency eta _t, by applying the anti-vibration that portion, it is possible to effectively reduce the noise of underwater sound transceivers.

Conventionally, for this purpose, each point of the hull has been vibrated and vibrations caused by the vibrations have been measured. However, noise caused by underwater propagation and noise caused by solid propagation are separated. it is not possible, it is difficult to identify the cause and part the conversion efficiency eta _t large noise. In view of the above circumstances, the present invention provides an acoustic sound wave efficiency when an exciting force at each point of a measured object such as a hull is converted into underwater sound waves, propagates underwater, and further converted into noise of a underwater sound wave receiver. It is an object of the present invention to provide an acoustic conversion efficiency measuring method capable of determining η _t with high accuracy separately from solid-state propagation, and a measuring apparatus suitable for implementing the measuring method.

[0007]

According to the sound conversion efficiency measuring method of the present invention, which achieves the above object, an underwater acoustic wave receiver is mounted, and at least a part thereof is added to each point of an object to be measured which is arranged in water. A sound conversion efficiency measuring method for measuring a conversion efficiency of a vibration force into a signal received by the underwater acoustic wave receiver for each point of the measured object, wherein a sound source is arranged in water and the sound source is The sound pressure of the sound radiated from, the vibration of a predetermined point of the measured object caused by the sound, and the signal level of the signal caused by the sound are measured, and based on the sound pressure, the vibration, and the signal level, The conversion efficiency of a predetermined point is obtained.

In the sound conversion efficiency measuring method of the present invention, a sound sensor for measuring the sound pressure and a vibration sensor for measuring the vibration are arranged at substantially the same distance from the sound source. It is preferable to measure sound pressure and vibration, respectively. Further, the acoustic conversion efficiency measurement of the present invention, the sound pressure p ', the acceleration of the vibration alpha, when the signal level v, the conversion efficiency eta _t, conversion efficiency eta _t has the formula η _t = C · <α ² > · <v ² > / <p ′ ² > ² (1) where C is a constant and <…> represents an average value of.

The acoustic conversion efficiency measuring apparatus according to the present invention is provided with an underwater acoustic wave receiver, and receives an exciting force applied to each point of an object to be measured which is at least partially disposed underwater by the underwater acoustic wave receiver. A sound conversion efficiency measuring device for measuring the conversion efficiency to a signal to be measured for each point of the measured object, comprising: (1) a sound source that radiates sound into water; and (2) a vibration of each point of the measured object. Vibration sensor to detect (3) Sound sensor to detect sound pressure of sound in water (4) Conversion efficiency calculation unit for obtaining the above conversion efficiency based on output of vibration sensor, output of sound sensor, and output of underwater sound wave receiver It is characterized by having.

In the above-described sound conversion efficiency measuring apparatus of the present invention, the apparatus has a contact surface which is in contact with each point of the object to be measured, and the contact surface is brought into contact with a predetermined point of the object to be measured. It is preferable to provide a measuring head to which the sound source and the sound sensor are fixed so that the distance between the predetermined point and the sound source and the distance between the sound source and the sound sensor are substantially equal to each other.

[0011]

Here, as an example, the measurement principle of the present invention will be described by taking a hull 1 as shown in FIG. 9 as an example of an object to be measured according to the present invention and an underwater acoustic wave transceiver 2 mounted on the hull 1 as an example. FIG. 1 is a diagram showing a relationship between excitation of a predetermined point on a hull and noise of an underwater acoustic wave receiver, and FIG. 2 is a diagram showing a model of the underwater propagation system.

[0012] A certain point of the hull 1 is determined by an excitation force <F^Two > (<…>
Represents the average of ...)
Sound pressure <P^Two > The sound is emitted and the sound propagates through the water
Enters the underwater acoustic wave transmitter / receiver 2 and
Sound pressure signal (noise) <v^Two > Is received.
At this time, as shown in FIG.^Two > Sound pressure <
P^Two > Conversion efficiency to η_rad , Sound pressure <P^Two > Signal <v
^Two > Conversion efficiency to η _s And the excitation force <F^Two >
Signal <v^Two > Total conversion efficiency η_tIs η_t = Η_rad ・ Η_s .. (2)

Therefore, in principle, each point of the hull is vibrated with a predetermined vibrating force <F ² >, and if the signal <v ² > of the underwater acoustic wave transceiver 2 at that time is observed, the total conversion efficiency η _{Although t} is likely to be required, using this principle it is necessary to excite each point of the hull with a fairly strong excitation force, which will radiate sound waves into the water and simultaneously generate considerable solid vibration. The solid vibration propagates through the hull and enters the underwater acoustic wave transceiver 2. This is why underwater propagation and solid propagation could not be separated conventionally.

Subsequently, the principle of the vibration method for directly vibrating the hull will be described in more detail, and then the measurement principle in the present invention will be described. FIG. 3 is a diagram illustrating the principle of measuring the sound conversion efficiency by the conventional vibration method. Elastic material 10
Is applied with a hammer or the like to apply a force F to the elastic material 10. The force F is detected by a load cell attached to the hammer or an acceleration sensor (not shown) attached to the elastic material 10, and the elastic material 10 is detected. The sound pressure p of the sound radiated from the elastic material 10 by being hit is detected by the microphone.

The acoustic conversion efficiency η _rad is defined as _follows : η _rad = W _ac / W _vibr (3) where W _ac is acoustic power and W _vibr is excitation power. Here, _assuming that the sound power W _ac is r, the distance to the microphone for detecting the sound pressure p is r.

[0016]

(Equation 1)

Where ρ _o is the density of the acoustic medium and C _o is the velocity of a longitudinal wave propagating in the acoustic medium. On the other hand, the power W _vibr of the excitation force is <V ²
> Is the mean square value of the surface wave velocity of the material, and Zi is the mechanical impedance of the hull.

[0018]

(Equation 2)

(D. Ross, Mechan)
ics of UnderwaterNoise, Pe
rgamon Press, (1976), 135-1
40. Substituting these into equation (3) gives

[0020]

(Equation 3)

Is derived. Accordingly, the sound conversion efficiency η _rad is obtained by substituting the force F and the sound pressure p detected as described above into the equation (6). FIG. 4 is an explanatory diagram of the law of acoustic reversibility, and shows a state where vibration is generated on the surface of the material 10 due to the sound radiated from the sound source 20 near the material 10. In the figure, U is the intensity of the sound source, and V is the surface wave velocity generated on the material 10 by the incident sound.

These U and V have the following relationship based on the law of acoustic reversibility between F and P shown in FIG. 3 (for example, “T. ten Wolde, Reciprocit”).
y experiments on the tran
mission of sound in shop
s, Ph. D. thesis. Tech. Un. Del
ft. Pubi. Hooglond & Waltma
n, Delft, (1973) "," HF Stee
nhoek, T .; ten Wolde, "Therec
iprocal measurement of me
mechanical-acoustic trans
fer functions ", Acoustica,
Vol. 23, (1970), 301-305. "
"T.tenWolde, Onthe validit
y and application of reci
proccity in acoustic, mec
hano-acoustic and other
dynamic systems, Acoustic
ical, Vol. 28, (1973), 23-3
2. "," T. ten Wolde, JW Verh
eij, H .; F. Steenhoek, Recipro
city method for the measure
rement of mechano-acousti
cal transfer functions, Jo
urn. Sound & Vibr. , Vol. 42,
(1975), 49-55. "reference).

(P / F) _{U = 0} = (V / U) _{F = 0} (7) where U = 0 indicates that there is no sound source in the vicinity, and F = 0
Indicates that there is no excitation force on the material 10.
Here, the surface wave acceleration is α, the angular frequency at that time is ω,
The surface wave velocity V of the material 10 is calculated as V = V ₀ · exp (−jω
Assuming that t), α = −jωV, and therefore, Expression (7) becomes (p / F) _{U = 0} = − (α / jω · U) _{F = 0} (8) From this relationship, the acoustic radiation efficiency η _ac in the case of FIG. 4 is obtained as follows.

Equation (8) of the acoustic reversibility law and the sound source 20
(RD Ford, Introd) between the sound pressure p 'measured at a position r' away from the sound source and the sound source intensity U
action to Acoustics, Elsev
ier Publ. Co. Ltd. , (1970). Reference) jωU = (4πr '/ ρ o) p' ... (9), acoustic conversion efficiency η _rad is,

[0025]

(Equation 4)

Can be expressed as At this time, assuming that r = r ′ in order to simplify Expression (10), the acoustic conversion efficiency η _rad becomes

[0027]

(Equation 5)

The sound pressure p and the table measured on the surface of the material
Sound conversion efficiency η from surface acceleration α_rad Can be calculated by
Wear. FIG. 5 is a diagram illustrating the principle of measurement according to the present invention. Sound source underwater
Underwater sound pressure of the underwater sound source <p '^Two > Measure
You. Also, the vibration of the hull <α^Two >
The acoustic conversion efficiency η of the hull based on the acoustic reversibility law described above
_rad Ask for. Also, the signal level of the underwater acoustic wave receiver <v
^Two > Underwater sound pressure <p '^Two Signal for>
Level <v^Two > Sound conversion efficiency η_s (See Figure 2)
And thus the total sound conversion efficiency η
_t Is required. Specifically, Equation (11) is replaced with Equation (2).
Substitute,

[0029]

(Equation 6)

## EQU1 ## In this equation (12), the measured water
Medium sound pressure <p '^Two >, Vibration <α^Two >, Signal level <v^Two >
To the total sound conversion efficiency η
_t Can be requested. Such measurements are taken at each point on the hull.
, The sound conversion as shown in FIG.
Efficiency η_t Contour lines can be drawn. Sound conversion efficiency η
_t By taking measures against vibrations in large areas of
The noise of the receiver can be effectively reduced.

[0031]

Embodiments of the present invention will be described below. FIG.
Is a configuration diagram of an embodiment of a sound conversion efficiency measuring device of the present invention,
FIG. 7 is a schematic diagram showing a state where the sound conversion efficiency of the hull is measured using the sound conversion efficiency measuring device shown in FIG.

The underwater sound source 31 is provided in the sound conversion efficiency measuring device 30 shown in FIG.
Is driven by an oscillator 32 to emit sound waves into water. The acoustic conversion efficiency measuring device 30 includes an underwater sound source 31.
An underwater microphone 33 that picks up the sound pressure p ′ of the underwater sound wave radiated from the underwater sound source, and a plurality of vibration pickups 34,. As shown in FIG. 7, the plurality of vibration pickups 34,..., 34 are attached to the respective measurement points of the hull so as to pick up vibration at the measurement points. The sound pressure p ′ of the underwater sound wave picked up by the underwater microphone 33 is directly measured by the measuring device 3.
The vibration α of the hull detected by the vibration pickups 34,..., 34 is input to the measuring instrument 35 via the switch 36. In addition, the underwater acoustic wave transceiver 2 (FIG. 7)
2) is also input to the measuring device 35. The underwater sound source 31 and the underwater microphone 33 are sequentially arranged in the vicinity of each measurement point. At the same time, the switching unit 36 is sequentially switched so that the detection signal of the vibration pickup 34 at the measurement point is input to the measurement unit 35. Is measured. For instrument 35 in its respective measuring point, an acoustic conversion efficiency eta _t is determined based on the aforementioned equation (12).

The acoustic conversion efficiency η _t of each measurement point obtained by the measuring device 35 is input to the computer 37, and the computer 37 determines the contour line of the acoustic conversion efficiency η _t , and the contour line is displayed on the CRT display 38. You. Thus, it is possible to know the distribution of the acoustic conversion efficiency eta _t hull. FIG. 8 is a diagram showing a measuring head to which an underwater sound source and an underwater microphone are fixed.

An underwater sound source 31 and an underwater microphone 33 are fixed to the measuring head 40. The measuring head 40 is suspended by a rope 41, and the measuring head 40 is operated by operating the rope 41 on the deck. Is moved to each measurement point. In the measurement head 40, a constant contact surface 42 is always in contact with the hull at the time of measurement, and in this state, the distance between the underwater sound source 31 and the measurement point of the hull, the underwater sound source 31 and the underwater microphone 33, Are configured so that the distance between them is equal. As a result, r = r ′, which was assumed in obtaining the equation (11), is guaranteed, and (1)
Using the equation (11) instead of the equation (0), the sound conversion efficiency η _rad
Can be requested. However, even if the distance between the underwater sound source 31 and the measurement point of the hull and the distance between the underwater sound source 31 and the underwater microphone 33 are different, the distances are measured in advance based on the equation (10). The sound conversion efficiency can also be obtained by using

[0035]

As described above, according to the present invention,
With respect to the excitation force of each point of the measured object, the conversion efficiency η _{t of} only the influence of underwater propagation on the signal received by the underwater acoustic wave receiver can be obtained, thereby reducing the noise of the underwater acoustic wave receiver. Effective anti-vibration measures can be taken.

[Brief description of the drawings]

FIG. 1 is a diagram showing a relationship between excitation of a predetermined point of a hull and noise of an underwater acoustic wave receiver.

FIG. 2 is a diagram showing a model of an underwater propagation system.

FIG. 3 is a diagram illustrating the principle of measuring acoustic radiation efficiency by a conventional vibration method.

FIG. 4 is an explanatory diagram of an acoustic reversibility law.

FIG. 5 is a diagram illustrating a measurement principle of the present invention.

FIG. 6 is a configuration diagram of one embodiment of a sound conversion efficiency measuring device of the present invention.

FIG. 7 is a schematic diagram showing a state in which the acoustic conversion efficiency of the hull is measured using the acoustic conversion efficiency measuring device shown in FIG.

FIG. 8 is a diagram showing a measurement head to which an underwater sound source and an underwater microphone are fixed.

FIG. 9 is an external view of a hull.

FIG. 10 is a schematic diagram showing a flow of vibration propagating in a hull and sound propagating in water.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Hull 2 Underwater sound wave receiver 30 Sound conversion efficiency measuring device 31 Underwater sound source 32 Oscillator 33 Underwater microphone 34 Vibration pickup 35 Measuring device 36 Switching device 37 Computer 38 CRT display 40 Measurement head

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Mutsuo Takashima 781 Shin-Yoshida-cho, Kohoku-ku, Yokohama-shi, Kanagawa Prefecture Inside JR RC Special Machinery Co., Ltd. 72) Inventor Akira Shinohara 4-9-18 Nakagosho, Nagano City, Nagano Prefecture

Claims (5)

(57) [Claims] An underwater acoustic wave receiver is mounted, and at least a part of the excitation force applied to each point of an object to be measured placed in water,
The conversion efficiency into a signal received by the underwater acoustic wave receiver,
A sound conversion efficiency measuring method for measuring each point of the measured object, wherein a sound source is disposed in water, a sound pressure of a sound radiated from the sound source, a predetermined point of the measured object caused by the sound. And measuring the signal level of the signal caused by the vibration and the sound, and obtaining the conversion efficiency of the predetermined point based on the sound pressure, the vibration and the signal level. 2. A sound sensor for measuring the sound pressure,
The method according to claim 1, wherein vibration sensors for measuring the vibration are arranged at substantially equal distances from the sound source, and the sound pressure and the vibration are measured, respectively. 3. When the sound pressure is p ′, the acceleration of the vibration is α, the signal level is v, and the conversion efficiency is η _t , the conversion efficiency η _t is _expressed by the following equation: η _t = C · <α ² > · <v ² > / <p ′ ² > ^{2 wherein} C is a constant and <... Represents an average value of... 4. An apparatus for mounting an underwater acoustic wave receiver, wherein at least a part of the object under test is placed in water,
The conversion efficiency into a signal received by the underwater acoustic wave receiver,
A sound conversion efficiency measuring device that measures each point of the measured object, a sound source that emits sound into water, a vibration sensor that detects vibration of each point of the measured object, A sound sensor that detects a sound pressure; and a conversion efficiency calculation unit that obtains the conversion efficiency based on an output of the vibration sensor, an output of the sound sensor, and an output of the underwater sound wave receiver. Sound conversion efficiency measurement device. 5. A contact surface which is in contact with each point of the object to be measured, wherein when the corresponding contact surface is brought into contact with a predetermined point of the object to be measured, the predetermined point and the sound source are separated from each other. The sound according to claim 4, further comprising a measurement head to which the sound source and the sound sensor are fixed so that a distance between the sound source and the sound sensor is substantially equal to each other. Conversion efficiency measurement device.