Measuring sound absorption below 100 Hz with a particle velocity-pressure sensor

Absorption is a difficult quantity to measure. The standards based on reverberation chamber measurements are limited to those above 100 Hz. Those based on commercially available impedance tubes are limited to 63 Hz and above. The Microflown impedance gun offers a newer approach to the measurement of absorption coefficients, but is limited to 300-8000 Hz in its commercial form. An extension to the commercial instrumentation to lower the operational range to 40 Hz is proposed. Measurements have been undertaken of dissipative type absorbers and panel absorbers to determine if this method can be used in the 40-100 Hz range. Results are reported and discussed along with the uncertainty in the measurement.

Shearer, D.J. and Dance, S. "Measuring absorption below 100Hz with particle velocity-pressure sensor", in Proceedings of Internoise, 2016.