Archives of Acoustics, 38, 2, pp. 191–195, 2013

Method of Testing of Sound Absorption Properties of Materials Intended for Ultrasonic Noise Protection

Dariusz PLEBAN
Central Institute for Labour Protection – National Research Institute

Efficient ultrasonic noise reduction by using enclosures requires the knowledge of absorbing properties of materials in the frequency range above 4 kHz. However, standardized methods enable determination of absorption coefficients of materials in the frequency range up to 4 kHz. For this reason, it is proposed to carry out measurements of the sound absorption properties of materials in the free field by means of a tone-burst technique in the frequency range from 4 kHz to 40 kHz at angles of incidence varying from 0 to 60. The absorption coefficient of a material is calculated from the reflection coefficient obtained by reflecting a tone-burst from both a perfectly reflecting panel and a combination of this panel and the sample of the tested material. The tests results show that mineral wool and polyurethane open-cell foam possess very good absorbing properties in this frequency range.
Keywords: ultrasonic noise; sound absorption coefficient; tone burst technique; sound absorbing mate- rial
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