@ARTICLE{Dobrucki_Andrzej_Sound-Absorbing_2010, author={Dobrucki, Andrzej and Żółtogórski, Bronisław and Pruchnicki, Piotr and Bolejko, Romuald}, volume={vol. 35}, number={No 2}, journal={Archives of Acoustics}, pages={157-164}, howpublished={online}, year={2010}, publisher={Polish Academy of Sciences, Institute of Fundamental Technological Research, Committee on Acoustics}, abstract={The physical phenomena occurring in sound-absorbing and insulating enclosures are subject of the present paper. These phenomena are: absorption in air and by the sound-absorbing material covering the walls and the coincidence effect. The absorption in the air can be neglected in small size enclosures for low ultrasonic frequencies (20-30 kHz). The coincidence plays a role in decrease of the sound insulation, however the main role play the leaks. The boards made of ceramic fibers have been chosen as the optimal sound-absorbing material. They are dense and have deeply porous structures. The enclosure for insulation of 20-kHz noise produced by a welding machine has been designed and manufactured, and reductions of 25 dB of peak and Leq levels have been achieved.}, type={Artykuły / Articles}, title={Sound-Absorbing and Insulating Enclosures for Ultrasonic Range}, URL={http://ochroma.man.poznan.pl/Content/107541/PDF-MASTER/71.pdf}, doi={10.2478/v10168-010-0014-4}, keywords={ultrasonic noise, sound absorbing and insulating enclosure, welder}, }