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WinZac 8 for Wide-frequency

Wide-frequency normal incident sound absorption coefficient measurement system Extension to eight microphones
makes more broadband absorption
coefficient measurement

  • ・Make frequency span wider
  • ・Make measurement highly accurate

WinZac 8 is a novel measurement system which allows you to measure sound absorption coefficient over wide frequency range with only one sample. Comparing with conventional impedance tube measurement systems, the upper limit of frequency span has been extended to double. This novel system is achieving wider frequency span, and higher accuracy and stability. In other words, WinZac 8 can greatly improve the measurement accuracy in the high frequency band, which was previously only possible with small tubes. WinZac 8 adopts "eight-microphone method", which has been developed by together with Industrial Technology Center of Okayama Prefecture, Japan. (Patent Pending)

Frequency image

Make frequency span wider

Wide-frequency normal incident sound absorption coefficient measurement systemWinZac 8 adopts the eight-microphone method which allows you to measure the extended frequency range with only one sample, as well as the conventional measurement at low to mid frequency complying with ISO 10534-2 and JIS A 1405-2. Taking advantage of WinZac 8, you can reduce the cost and workload to prepare plural samples significantly. Moreover, you can resolve the problems happened in conventional systems which used two different sizes of impedance tubes, especially for eliminating the data processing in overwrapped frequency range using two different sizes of samples.

In conventional method, to measure the wide frequency span, you needed to use two different size of impedance tubes and needed to prepare the two different sizes of samples as well.
However, when you measured sound absorption coefficient using two different sizes of impedance tubes and samples, you need

  • longer time to prepare samples,
  • more procedures to set samples, and
  • more spaces to keep samples in lab. And you met
  • acoustic characteristics of two samples may be different or fluctuating, and
  • measured absorption coefficient may be slightly different between two samples especially the sample having low air permeability.

These are unnecessary procedures and unwanted fluctuations which yields difficulties to process measured data. To use WinZac 8, you can resolve these issues, because WinZac 8 uses only one sample for measuring sound absorption coefficient with wide frequency span.

Make measurement highly accurate

WinZac 8 extends the upper frequency limit to double comparing with conventional system. It allows you to conduct more efficient sound absorption coefficient measurement to use the larger samples.

In conventional method, the internal diameter of impedance tube is required to be less than 0.58 times of the sound wavelength. Due to this limitation, you needed to use an impedance tube having small diameters if you wanted to measure the absorption coefficient at high frequency. For example, to measure the sound absorption coefficient at 5,000Hz, you needed to use the impedance tube with 40mm diameter or less.
However, if you use small tubes and sample, you needed to increase the number of samples and measurement for averaging to keep accuracy. The problems are,

  • variation in cutting the samples, and
  • harmful effect due to gap between sample and internal surface of tubes.

If you can use a larger sample, you can conduct more accurate and efficient measurement.

Measured example

Melamine foam (WinZac 8 100 diameter tube)

Melamine foam imageThe upper bound frequency of WinZac 8 100 diameter tube is extended to 5.8kHz, whereas the upper bound frequency of conventional impedance tube with same size is 1.8kHz.

In addition, the sound absorption coefficient between 2kHz and 5kHz is showing almost same characteristics as that of the conventional impedance tube 40 diameter tube. Moreover, at lower frequency bands, and WinZac 8 100 diameter tube is achieving more accurate results than conventional 40 diameter tube.

PET felt (WinZac 8 40 diameter tube)

PET felt imageThe upper bound of WinZac 8 40 diameter tube is extended to 10kHz, whereas the upper bound frequency of conventional impedance tube with same size is 4.8kHz.


100 diameter tube 40 diameter tube
Size of samples 100 mm 40 mm
Frequency span *1) 100 - 5.8 kHz 200 - 10 kHz
ISO / JIS method *2) 100 - 1.8 kHz 200 - 4.8 kHz
Eight microphone method 500- 5.8 kHz 1 k - 10 kHz
Measurement methods
  • 1. ISO 10534-2 and JIS 1405-2
  • 2. Eight-microphone method
Maximum number of microphones *3) 8
Measurable parameters
  • Sound absorption coefficient
  • Complex sound pressure reflection coefficient
  • Specific acoustic impedance
  • Characteristic impedance
  • Propagation constant
  • Effective density
  • Bulk modulus
  • Random incident sound absorption coefficient (estimation) Sound transmission loss
*1) Measurement frequency span is based on combining measurement complying with ISO 10534-2 / JIS 1405-2 and eight microphone method.
*2) ISO / JIS method means the method complying with ISO 10534-2 / JIS 1405-2.
*3) The number of microphones may be changed depending on the measurement method and desired acoustic characteristics.


1. A. Sanada, K. Iwata, H. Nakagawa, "Extension of the frequency range of normal-incidence sound absorption coefficient measurement in impedance tube using four or eight microphones", Acoust. Sci. & Tech. 39, 5, pp 335 - 342 (2018)
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