The current standard test methods for low frequency impedance of acoustic materials provided by ISO and American Society for Testing and Materials (ASTM) are not suitable for the newly discovered Resonance Sonic Material (RSM), which is of very high impedance. We have developed a reliable measurement technique that takes into account the multiple-reflection of the impedance sample/tube/speaker system. The complex transmittance (both amplitude and phase) of samples with very high impedance (low transmission) can be measured, even at wavelengths where the tube is resonant, or several times the tube length....[ Read more ]

The current standard test methods for low frequency impedance of acoustic materials provided by ISO and American Society for Testing and Materials (ASTM) are not suitable for the newly discovered Resonance Sonic Material (RSM), which is of very high impedance. We have developed a reliable measurement technique that takes into account the multiple-reflection of the impedance sample/tube/speaker system. The complex transmittance (both amplitude and phase) of samples with very high impedance (low transmission) can be measured, even at wavelengths where the tube is resonant, or several times the tube length.

Five kinds of RSM samples are measured from 110Hz to 1200Hz. Three transmission dips near 200Hz, 500 Hz and 1100 Hz with transmission phase changes ~180° are observed from these manufactured RSM, showing localized resonance effect. They are in agreement with the theory, showing effective low sound isolation capability of these RSM's. Possible sources of error area are discussed.