JP2003083805A - Measuring technique of acoustic impedance and acoustic absorption coefficient - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technique for measuring accurately the acoustic impedance and the acoustic absorption coefficient of a sample such as a building material in the installed state on a cite. SOLUTION: In this measuring technique of the acoustic impedance and the acoustic absorption coefficient for measuring accurately the acoustic impedance and the acoustic absorption coefficient of the material installed on the cite, the acoustic impedance and the acoustic absorption coefficient of the material are measured by utilizing a usually existing noise without using a sound source speaker. In a room where the usually existing noise level is low and measurement is difficult as it is, a random noise is outputted, and measurement is performed by improving diffusion of the sound in the room.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to measurement of acoustic impedance and sound absorption coefficient of various samples such as building materials.

[0002]

2. Description of the Related Art Conventionally, as one of the methods for measuring the acoustic impedance and sound absorption coefficient of a material, a method using an acoustic tube and a precise installation condition between a sound source speaker, a microphone, and a sample are taken into consideration for measurement on site. The technique is being carried out. The conventional method for measuring the acoustic impedance of materials will be described below.

FIG. 3 is one of the techniques for measuring the acoustic impedance of a material using an acoustic tube. Place the sample on one side of the acoustic tube and the sound source speaker on the other side. Furthermore, a movable microphone (probe microphone) is installed in the center of the tube. The acoustic impedance of the material is determined by moving the microphone and measuring the pattern of the standing wave near the surface of the material, that is, the position where the first Pmin occurs.

FIG. 4 shows a method of measuring the acoustic impedance of a material using an acoustic tube, as in the above. The type of microphone and the installation method are different from the above method, and the acoustic impedance of the sample surface is obtained from the transfer function between two points measured by two fixed microphones.

FIG. 5 and FIG. 6 show a method for measuring the acoustic impedance of a material in the field. However, an appropriate positional relationship between a sound source, a sample, and a microphone and a kind of a sound source are obtained, and the acoustic impedance of the material is obtained according to the conditions. ing.

Further, the measuring method for obtaining the sound absorption coefficient of a material is
It is specified in JIS A1408 and ISO 354. There is a method of measuring the sound absorption coefficient in the reverberation room method. A sample is placed in a reverberation room with a reverberation time of T seconds, and the sound absorption coefficient of the sample is calculated from the change in reverberation time using Sabine's reverberation equation.

[0007]

The problems of the conventional acoustic impedance measuring method described above are 0003 above.
In the cases of the items [0004] and [0004], the measurement target is limited to a small sample, and the characteristics are different from those of the sample installed in the field with a large size.

Further, in the case of the item 0005, the setting and control of the characteristics of the sound source and the positional relationship between the sound source, the sample, and the microphone are greatly affected, and the setting and control thereof are complicated. Moreover, it is difficult to obtain the characteristics of the material at low frequencies in a general room by this method.

Although the sound absorption coefficient of the sample can be obtained by the method of paragraph 0006, the acoustic impedance cannot be obtained. Furthermore, a large-scale equipment such as a reverberation room and a sample of about 10 square meters is required, and it is difficult to realize a perfect diffuse sound field which is a setting condition of the reverberation room for measurement.

The present invention is intended to solve the above problems of the conventional measuring method, does not require a special device or precise installation conditions, and does not require the acoustic impedance and the material impedance at any place. The purpose is to measure sound absorption.

[0011]

In order to achieve the above-mentioned object, the present invention is characterized by measuring the acoustic impedance and the sound absorption coefficient without using a sound source speaker. By measuring in this way, the acoustic impedance and the sound absorption coefficient can be measured at any place as long as there is some noise.

Further, the means for solving the problem of the item 0008 is to improve the diffusivity in the room by using a plurality of random noise sources and to measure the acoustic impedance and the sound absorption coefficient.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described with reference to the drawings.

As shown in FIG.
A microphone is installed and the transfer function between the two points at this time is obtained. Furthermore, the same measurement can be performed at several sound receiving points, and they can be averaged by energy to obtain the acoustic impedance and sound absorption coefficient of this sample.

Next, when random noise is used for the sound source, the sound source is randomly placed as shown in FIG. 2 and the same measurement as above is performed. This measurement is carried out under several kinds of sound source arrangement conditions in which sound source positions are different, and measurement is performed at several sound receiving points in the same manner as described above, and by averaging them, the acoustic impedance and sound absorption coefficient of this sample can be obtained.

【The invention's effect】

As described above, the method for measuring the acoustic impedance and the sound absorption coefficient of the material of the present invention is the microphone and the FF.
It is possible to measure the acoustic impedance and sound absorption coefficient of a material installed in the field simply by using a simple device such as a T analyzer or a digital filter.

Even when random noise is used for the sound source, the acoustic impedance and the sound absorption coefficient of the material can be easily measured in the same manner as described above if the sound sources are randomly installed without giving precise installation conditions.

[Brief description of drawings]

FIG. 1 is an installation diagram of an embodiment of the present invention and a measurement method.

FIG. 2 is one of the embodiments of the present invention when random noise is used as a sound source

[Fig. 3] Example of conventional technology, one of acoustic tube methods, standing wave method (JIS A1405, ISO10534-1)

[FIG. 4] Example of conventional technology, one of acoustic tube method, and two-microphone method (ISO10534-2)

FIG. 5: Example of prior art, reflection method 1

FIG. 6 is a reflection method 2 according to an embodiment of the related art.

Claims (3)

[Claims] 1. A method of measuring acoustic impedance and sound absorption coefficient of a material installed in a site, which does not use a sound source speaker, but uses sound (noise) that is normally present. 2. The method for measuring acoustic impedance and sound absorption coefficient according to claim 1, when the noise level is low,
Method of measuring acoustic impedance and sound absorption coefficient by using multiple random noises 3. The method for measuring acoustic impedance and sound absorption coefficient according to claim 1, wherein a plurality of random noises according to claim 2 are installed even in a place such as a small room where sound diffusivity is poor. Method for Measuring Acoustic Impedance and Sound Absorption Coefficient by Improving Noise