A low‐cost digital system based on an 8‐bit Apple II microcomputer has been designed to provide on‐line control, data acquisition, and evaluation of sound absorption measurements in gases. The measurements are conducted in a resonant tube, in which an acoustical standing wave is excited, the excitation removed, and the sound absorption evaluated from the free decay envelope. The free decay is initiated from the computer keyboard after the standing wave is established, and the microphone response signal is the source of the analog signal for the A/D converter. The acquisition software is written inassemblylanguage and the evaluation software inbasic. This paper describes the acoustical measurement, hardware, software, and system performance and presents measurements of sound absorption in air as an example.