Low frequency in situ metrology of absorption and dispersion of sound absorbing porous materials based on high power ultrasonic non-linearly demodulated waves
- 作者：Bernard Castagné ; de ; Alexei Moussatov ; Denis Lafarge ; Mohamed Saeid
- 关键词：Acoustic in situ measurements ; Portable instrumentation ; Ultrasonic demodulation in air ; Non-linear high power ultrasonics ; Absorption coefficient ; Dispersion ; “ ; Equivalent fluid” ; model ; Porous materials ; Automotive felts ; Compressed sound ab
- 刊名：Applied Acoustics
- 出版年：2008
- 期刊代码：12_0003682x
- 类别：et
- 出版时间：July 2008
- 卷：69
- 期：7
- 页码：634-648
- 文件大小：957 K
摘要
The present work is related to acoustic in situ free-field measurements of sound absorption in porous materials, such as cellular plastic foams, glass–wool or recycled felt materials. The emphasis is given towards fine metrology of absorption in view of potential industrial applications. A powerful ultrasonic array working at 40 kHz is used. It enables to measure absorption acoustical data down to 100 Hz due to the exploitation of the non-linear ultrasonic demodulation phenomenon in air. Fine measurements of acoustic absorption are compared to numerical predictions based on the “equivalent-fluid” model (when the squeleton frame is motionless), and to some measurements performed on a Brüel and Kjaer impedance tube. Dispersion curves are also measured and compared to the numerical predictions for some automotive felt materials which are compressed at various ratios. Data obtained with a dedicated portable instrument are also discussed for the same type of materials and configurations.