Abstract
A new method for measuring impedance has been used for evaluating the normal surface impedance of three foams in free field. The results have been interpreted using the Biot theory, the two dilatational waves being taken into account. It has been pointed out from the theory that, for high flow resistance, the ratio of the acoustical velocities of the frame and the air is close to 1 at the surface of the foam. This ratio decreases with flow resistance but is never negligible for the studied foams. For foams with high flow resistance, the contributions of the two waves must be taken into account when calculating the impedance, and a description with only one wave would not be realistic. For foams with medium flow resistance, the one-wave approximation for calculating the surface impedance is a good approximation in the whole range of acoustical frequencies.
Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
