N2 - 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. L1 - http://journals.pan.pl/Content/101517/PDF/06-paper.pdf L2 - http://journals.pan.pl/Content/101517 PY - 2013 IS - No 2 EP - 195 DO - 10.2478/aoa-2013-0022 KW - ultrasonic noise KW - sound absorption coefficient KW - tone burst technique KW - sound absorbing material A1 - Pleban, Dariusz PB - Polish Academy of Sciences, Institute of Fundamental Technological Research, Committee on Acoustics VL - vol. 38 DA - 2013 T1 - Method of Testing of Sound Absorption Properties of Materials Intended for Ultrasonic Noise Protection SP - 191 UR - http://journals.pan.pl/dlibra/publication/edition/101517 T2 - Archives of Acoustics