The Practicality of Using Generic Acoustical Equipment in Impedance Tube Design

Abstract

The impedance tube method is commonly employed to measure the acoustical properties of materials, but commercial versions are prohibitively expensive for researchers lacking access to well-funded acoustical laboratories. A significant expense in traditional impedance tube setups is the pressure field microphones. This study explores the feasibility of using low-cost consumer-grade electret microphones, which are substantially cheaper than their pressure field counterparts. Our impedance tube design was validated and tested with high-cost pressure field microphones, contrasting it with electret microphones priced under one US dollar (USD). The findings reveal that the sound absorption coefficient can still be effectively and accurately measured using inexpensive microphones, subject to suitable signal conditioning and accurate microphone calibration. The trade-off is a slight loss of accuracy for the low-end frequency range of < 250 Hz.