JPS62251799A - Propagation direction controller for sound wave - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a sound wave propagation direction control device, and more particularly to a sound wave propagation direction control device that refracts the propagation direction of a sound wave in a predetermined frequency ML band.

[Background technology] In recent years, traffic noise generated when vehicles pass along railway lines and roads has become a problem, and countermeasures such as installing soundproof walls have been taken, but since sound waves are diffracted, In addition, with the mechanization of office processing (OA), computers, word processors, and other devices are increasingly used in offices, and dot impact printers are often used as output devices. has been done. Dot impact printers like this make a lot of noise when they operate, so they have to be partitioned! ! ! Since it is not possible to prevent the diffraction of sound waves, the office environment due to noise has become a problem. Furthermore, sky ill! The sound of the device's fan blowing air and the sound of the motor! ! Since the air conditioner cannot block the air inlet and outlet and surround it with a wall, it is not possible to provide sound insulation. As described above, the conventionally provided sound insulation devices do not sufficiently consider the diffraction of sound waves, and in that sense, the sound insulation effect cannot be said to be sufficient.

On the other hand, a device is being considered that prevents the propagation of sound waves to unnecessary areas by refracting the traveling direction of the sound waves while transmitting the sound waves. That is, as shown in FIG. 14, by arranging a plurality of baffle plates 2 at a distance from each other in a direction orthogonal to the traveling direction of waves and the traveling direction of sound waves, a kind of It acts as a low-pass filter and refracts the sound waves by utilizing the difference between the phase velocity of the sound waves within the device and the phase velocity of the surrounding sound waves. In this device, the distance ah between the centers of the baffle plates 2 in a plane perpendicular to the direction of sound wave propagation is related to the passing sound wave. It is necessary to set the height to 34 cm, which causes the problem of increasing the overall size. Also,
The problem is that the occupied area of the buff full plate 2 increases and the aperture ratio decreases, and it cannot be applied to sound sources that require a large aperture ratio (such as when ventilation is required for air conditioning, etc.). There is.

[Object of the invention] The present invention has been made in view of the above points, and its main purpose is to refract sound waves in a specific direction so that the sound can be heard only in a specific location. Sound wave propagation direction control to avoid propagation of sound waves to unnecessary locations 5! Another object of the present invention is to provide a sound wave propagation direction control device that can have a relatively large aperture ratio.

[Disclosure of the Invention] (Structure) Sound wave propagation direction control according to the present invention! In the i11 position, a straight hollow tube made of a thin-walled viscoelastic material is used as a control element for controlling the phase velocity of a sound wave, and the plurality of control elements are arranged so that their axial directions are substantially parallel to each other. When placed 6
In this configuration, control elements having different phase velocities of passing sound waves in one direction in a plane orthogonal to the axial direction of the control I element are arranged so that the phase velocities of the passing sound waves increase sequentially. It is formed to have an aperture ratio and also refracts sound waves to prevent them from propagating to unnecessary locations.

(Basic Principle) First, the basic principle of the present invention will be explained. In the following explanation,
As shown in FIG. 8, a straight hollow cylindrical body is used as the control element 1, but the present invention is not limited to a cylindrical body, and may be a cylinder having another cross-sectional shape. When a sound wave passes through such a control line 1, the tube wall of the control element 1 vibrates as shown by the arrow in FIG. However, a unit length portion of a hollow body with both ends open can be considered as an equivalent electric circuit as shown in FIG. That is, the inertance of the gas in the tube La%, the acoustic capacitance of the gas in the tube Ca, the inertance of the tube wall Lm, the humpliance of the l wall Cm, and the conductance G of the tube wall.
The acoustic characteristics of a unit length of the control element 1 are determined by w. The mass per unit length of the cross-sectional area S and ff of the tube is lI+ (=2πrpwt: ρ- is the density of the tube wall)
, the inner diameter of the tube is r1, the wall thickness of the tube is W, and the Young's modulus of the wall is E,
? ? If the compliance of the wall conguctance is, the density of the gas inside the tube is ρ, the bulk elastic modulus of the gas inside the tube is K, and each frequency of the sound wave is ω (=:'rf: f is the frequency of the sound wave), each parameter is Each is expressed by the following formula.

La=ρ/S Ca=S/K Lw=m/4 y "r2 C spear=2πr"/Et Gw=K ω Therefore, the resonant frequency fr of the control element 1 is calculated by the following equation 2% In the equivalent electric circuit described above, By introducing equivalent conductance Geq and equivalent capacitance Ceq expressed by the following equations, the equivalent electric circuit of the PIIjS diagram can be further replaced with the equivalent electric circuit of FIG. 10.

Geq=Gw/((1u2Lwcw)2+ω2Gw2L
w2) If we find the phase constant β of the equivalent electric circuit in Figure 10, we have found the phase constant of the sound wave passing through the pipe, and can we define the phase velocity Vp from that phase constant β? Wear.

+ω2LaCeq))l/2 vp=ω/β As is clear from the above equation, the equivalent conductance G
Since eq and the equivalent capacitance Ceq have seven singularities at the resonant frequency, the phase velocity Vp changes greatly near the resonant frequency, as shown in FIG. In addition, since the phase velocity Vp is calculated for a unit length, it is clear that it is a function of the length of the control 11 summary 1. Furthermore, the phase constant β includes the density of the tube wall, Young's modulus, and inner diameter. Since it is folded in, it can be seen that it is a function of these. FIG. 12 shows the experimental results of the frequency characteristics of the phase velocity for this control element 1.

In this way, it can be seen that the phase velocity changes significantly at a specific frequency. Here, the measurement device includes a speaker 11 that transmits sound waves from one end of the control I element 1 into the *III element 1, and a speaker 11 that is inserted into the control 1W cable 1 and located at a place inside the control element 1, as shown in the tJS13 diagram. a probe microphone 12 that picks up sound from the probe microphone 12; a signal generation circuit 13 and an amplification circuit 14 that generate an electric signal to be output from the speaker 11; and a measurement amplification circuit 15 that amplifies the sound picked up by the probe microphone 12.

A phase meter 16 detects the phase of the sound output from the measurement amplifier circuit 15, and a phase meter 16 controls the frequency of the signal output from the signal generation circuit 13 and records the output of the phase meter 16 to determine the phase velocity within the control element 1. A calculation control unit that calculates r! 117
Tode! R is made. Here, the arithmetic control II device e17
is composed of a microcomputer, etc. Control element 1 has a Young's modulus of 7. OXl 0'[N/z”
l (measured by a complex modulus measuring device, i.e., a viscoelastic spectrometer), and the density is 1190 [Ag/i
A tube made of +31 silicone rubber was used, the inner diameter was set to 25ijI, and the thickness of the tube wall was set to 0.3mm.

By utilizing the above-mentioned characteristics, a difference occurs between the phase velocity within the control element 11 and the phase velocity outside the control element 1, so that the sound wave can be refracted by using this control element. In the following embodiments, a plurality of the above-mentioned cylindrical control elements 1 are used to control the propagation direction of sound waves.

(Example 1) Fig. 1 OtFt! As shown in FIG. 12, a plurality of control elements 1 are arranged with their axial directions parallel to each other, and one end surface of the control elements 1 into which sound waves are introduced is disposed on the same plane.

In a plane perpendicular to the direction of propagation of the sound wave, control elements 1 having the same length in the axial direction are arranged in a row in the horizontal direction, and control elements 1 having a longer length in the axial direction are arranged in a row in the vertical direction. be done. As mentioned above, the control element 1 delays the phase velocity inside the tube compared to the phase velocity outside the tube below the resonance frequency, so the longer the tube length, the greater the phase delay, as shown in Figure 2. , the wavefront W s i that was orthogonal to the axial direction of the control element 1 before being introduced into the control element 1 is
After passing through the control element 1, the wave surface Wso becomes inclined with respect to the axial direction of the control element 1, and the sound wave is refracted. Here, the control element 1 is formed in the same manner as that used in the experiment, and the distance between the outer circumferences 1117 of the control I elements 1 arranged one above the other is 5xzs, and the difference in length of the control elements 1 adjacent above and below is 5xzs.
0111, the phase velocity of the 500Hz sound wave in the tube is 100z/s, and the refraction angle is 40% downward.
It became a degree.

The number of control elements is selected depending on the area of the area to be sound-insulated, and the minimum unit may be one row in the horizontal direction, and if there are two or more rows in the vertical direction, the above effect can be achieved. can play.

(Example 2) In this example, sound waves are refracted in the same manner as in Example 1 by arranging control elements 1 having different tube wall densities or Young's moduli. That is, as shown in Figure @3, the length of the control element 1 in the axial direction is set to be the same length, and only the density or Young's modulus of the tube wall is changed. For example, when changing only the density while keeping Young's modulus constant,
The lower density is set to be larger in the longitudinal direction. Conversely, when the density is kept constant and only the Young's modulus is changed, the lower Young's modulus is set to be smaller in the longitudinal direction. Here, control elements 1 having the same density or Young's modulus are arranged in the lateral direction. The phase velocity within the m-control element 1 becomes smaller as the density of the 1g wall becomes larger, as shown in FIG. 4, and becomes smaller as the Young's modulus becomes smaller, as shown in FIG.

Therefore, in the above configuration, the wavefront Wso of the sound wave passing through the control element 1 is inclined downward with respect to the axial direction of the control element 1, as in the first embodiment. Here, the control element 1 used in the measurements shown in the rPjA diagram and FIG. 6X10'N/
In Wei 2 and Figure 5, the density of the tube wall material is 1110k.
g/x'. *The bulk elastic modulus of the gas inside the tube was measured as 1.31 x 10-''.

As described above, by changing the density and Young's modulus of the material of the tube wall of the control element 1 and also changing the length of the control I element 1 as in Example 1, it is possible to further refract sound waves. It is something.

(Example 3) In this example, control g! with different inner diameters is used. By using the cable 1, the phase velocity within the control 1 element 1 is controlled.

In other words, the larger the inner diameter of control %-11, the smaller the phase velocity, so as shown in Fig. 16, the control elements 1 having the same inner diameter are arranged in the horizontal direction, and the lower one has the larger inner diameter in the vertical direction. If the control element 1 is arranged, the wavefront Wso of the sound wave that has passed through the control element 1 will be refracted downward.

When the phase velocity is actually measured by changing the inner diameter of the control element 1, the results shown in FIG. 7 are obtained. Here, the thickness of the tube wall is 0.0016z, and the Young's modulus is 4°6 × 106
[N/z21, the density was 1110 kg7m3, and the bulk elastic modulus of the gas in the tube was 1.31 x 10-10. As can be seen from this measurement result, 1
Below around kHz, the larger the inner diameter of the tube, the smaller the phase velocity becomes (at 800 Hz, the radius is 7
am, 8 IN, 9 +u+, and 10311, the phase velocity is 2951/8% 27 ON/S, respectively.
, 260 f/s, and 230 a/s), therefore, it is refracted downward by about 40 degrees at around 800 Hz.

It goes without saying that if this embodiment is combined with the configurations of embodiments 1 and 2, the refraction effect can be further increased.

In each of the above embodiments, the phase velocity is controlled for frequencies below the resonant frequency where the phase velocity changes rapidly, so if the resonant frequency is set to a high frequency, the refractable frequency band can be expanded. Can be done. In addition, even in the region above the resonance frequency, in the high frequency region, there is a region where the phase velocity becomes small depending on the Young's modulus and density of the tube wall, or the inner diameter of the tube, so it is not used in this region. If so, it would be possible to refract a single sound wave even in areas other than the low frequency range.

[Effect of the Invention 1] As described above, the present invention controls the phase velocity of a sound wave in a hollow tube formed thinly from a material having viscoelasticity!
! A plurality of control elements are arranged so that their axial directions are substantially parallel to each other, and a control element in which the phase velocity of the passing sound wave differs in one direction in a plane perpendicular to the axial direction of the control element is arranged. Since they are arranged so that the phase velocity increases sequentially, the direction in which the sound waves travel can be refracted.
As a result, it has the advantage of preventing sound waves from propagating in unnecessary directions and allowing sound waves to propagate only in necessary directions. Furthermore, since the control element is made of a viscoelastic material and is formed into a thin straight tube shape, it has the advantage of good air permeability.

[Brief explanation of drawings]

Figure 1 is a schematic configuration diagram of the first embodiment of the present invention, Figure 2 is a side view of the same as above, Figure 3 is a schematic diagram of the second embodiment of the present invention, and Figures 4 and tpJ5 are the same as above. FIG. 7 is an explanatory diagram of the same operation as above; FIG. 8 is a perspective view showing control elements used in the present invention; FIG. 9 and FIG. The figure is an equivalent electric circuit diagram of 11 elements, Figures 11 and 12 are explanatory diagrams of the same operation as above, Figure 13 is a configuration diagram showing the measuring device of the control element used in the same, and Figure 14 is the direction of propagation of the subordinate rice. a perspective view showing a control device;
FIG. 15 is an explanatory diagram of the same operation as above. 1 is a control element. Agent Patent Attorney Ishi 1) 艮 7th 1st figure 5O 41 years old BAN [mzsl 9th figure. 10-a 11th Flash/1l IGHLHzJ Figure 13 Figure 5 Notification Danmin CHt1 Procedural Amendment (Voluntary) July 4, 1985

Claims (5)

[Claims] (1) A straight hollow tube made of a thin-walled viscoelastic material is used as a control element for controlling the phase velocity of a sound wave,
A plurality of control elements are arranged so that their axial directions are substantially parallel to each other, and control elements whose phase velocities of passing sound waves differ in one direction in a plane orthogonal to the axial direction of the control elements are sequentially arranged so that the phase velocities become larger. What is claimed is: 1. A sound wave propagation direction control device characterized in that the sound wave propagation direction control device is arranged so that (2) Propagation of sound waves according to claim 1, characterized in that the axial length of each control element is sequentially increased in one direction within a plane perpendicular to the axial direction of the control element. Directional control device. (3) Propagation of sound waves according to claim 1 or 2, characterized in that the inner diameter of each control element is sequentially increased in one direction within a plane orthogonal to the axial direction of the control element. Directional control device. (4) Claims 1 and 2, characterized in that the density of the material forming each control element is gradually increased in one direction within a plane perpendicular to the axial direction of the control element.
Alternatively, the sound wave propagation direction control device according to item 3. (5) Claims 1 and 2, characterized in that the Young's modulus of the material forming each control element is successively reduced in one direction within a plane orthogonal to the axial direction of the control element;
The sound wave propagation direction control device according to item 3 or 4.