The WinZac system realizes the measurement of normal incident sound absorption coefficient using the impedance tube and Windows based PC. A high-quality audio interface is used for measurement. All analysis is software based, so there is no need for special hardware such as FFT analyzer.
WinZac implements the measurement based on ISO 10534-2, ASTM E-1050 and JIS 1405-2. By measuring the transfer function between two points in the impedance tube using the FFT technique (two-microphone method), we are able to greatly shorten the measurement time compared to the standing wave ratio method. Calibration is also made in accordance with the standard above mentioned. WinZac measures transfer function data for correcting microphone mismatch. The result makes it possible to correct sensitivity and phase difference of microphones throughout the entire frequency bandwidth.
All measurements and analysis can be carried out by the software in Windows based PC which has high-quality audio interface as the front-end. No special FFT analyzer for exclusive use is needed (*1). As a result, WinZac has a very compact system configuration as its strong point.
*1: Power Amp. and Microphone Amp. are required.
Not only the normal incident absorption coefficient, but also it supports the measurements of transfer function, reflection coefficient, and specific acoustic impedance ratio. Predicting the random incident sound absorption coefficient of a material is also possible.
Moreover, it is possible to predict the characteristic impedance of the porous material, the propagation coefficient, effective density and the bulk modulus from the two measured resutls of different backed cavities (two-cavity method).
Normal incident absorption coefficient
Random incident absorption coefficient
Characteristic impedance
The frequency band which can be measured in impedance tube depends on the shape of the cross section and diameter of the tube. With our impedance tube, the wide frequency band (about 200 - 5000 Hz) can be measured at once. In other words, we do not need to measure the several frequency bands using different sizes of impedance tubes. So the problem due to the different sample and measurement system is not happen. Of course, doubled time for measurement and preparing the two samples for two different tubes with different diameter can be eliminated.
We designed both the software and hardware for ease of use, and support the process of developing acoustical materials. Since the software is designed for the material database development, it is easy to make comparison between several measurements on the same sample, for checking the variation and repeatability. By averaging the measurement results of certain number of times, a stable measurement result can be obtained. Moreover, the functions such as graphical display, or changing the format between narrow band, 1/1 octave band and 1/3 octave band, are included in the standard software. As for the hardware, we have developed a transparent acrylic sample holder of the impedance tube. This enables us to check the set up condition of the sample while measurement, and decreases the mistakes due to incorrect setup of the sample.
1/3 octave band display
transparent sample holder
Besides our standard impedance tube, the software can be applied for various tubes having different cross section and diameter easily.
We will support the needs of our customers. Feel free to contact to us.
By replacing the standard sample holder with the transmission tube, we can measure the transmission loss of the sample under the normal incident condition. In addition, we can estimate the parameters such as the characteristic impedance or the propagation constant for the porous material.
By using the loose supporting sample holder (patent pending) that we developed, it can greatly decrease the effect caused by vibration of the sample.
Loose supporting sample holder (1)
Loose supporting sample holder (2)
| Measurement method | Transfer function method (ISO 10534-2, ASTM E-1050 and JIS 1405-2) |
|---|---|
| Impedance tube | Acoustic Tube
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| Parameters can be measured |
Measurement using the reflecting method:
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| Frequency range | 200 - 5000 Hz (for narrow band measurement*2, 25°C)
(*2 depending upon the shape and internal diameter of the tube) |
| Calibration | Correction coefficient calculation by microphone switching (ISO 10534-2, ASTM E-1050, JIS 1405) |
| PC | OS: Microsoft Windows 2000 / XP System requirements: Pentium III or faster CPU and 128MB or more RAM is recommended) |
| Audio Interface | Ask us for the recommendations |