Abstract:

Measurement of the sound absorption coefficient using an impedance tube is prone to errors due to various reasons. Conventionally minimising the errors requires additional hardware or proper calibration of many components used for measurement. This paper proposes a new error correction mechanism using a filtering technique. A low cost impedance tube was designed, developed and its performance was compared with a commercially available high cost tube. The errors which arose during the measurement of the sound absorption coefficient were minimised using different types of filters (low pass, band pass, LMS filtering). The purpose of the filter is to eliminate unwanted signals or noise which occur during the processing of analogue signals in the experiment. The system proposed was tested using various porous and non-porous functional textile materials and the results validated. A significant reduction in error was obtained at all frequency ranges with digital filters.