A brief history of the standing wave tube

The standing wave tube is widely used to measure the absorption coefficient and surface normal impedance of materials, most often in accordance with ASTM standard E1050, in which a so-called two-microphone procedure is described. However, the standing wave tube method has a long and interesting history, having been used to measure acoustic absorption coefficients for more than 120 years, its first development being credited by several authors to Tuma in 1902. The initial pure tone procedures were entirely non-electronic and relied on sensitive flames or discs to quantify sound pressure. The first electronic implementation appeared in the 1920s and was based on using a “hot wire microphone” to measure the sound field. The pure tone procedure involving a traversing probe tube found its ultimate expression in work by Beranek (1947), Brüel and Kjaer (1955), and Champoux and Stinson (1991). The “modern” two-microphone, broadband procedure was introduced by Seybert and Ross in 1977 and has since been universally adopted as an efficient alternative to the pure tone procedure. The presentation will conclude with a description of the extension of the two-microphone procedure to four-microphone, transmission loss measurements, and recent multi-microphone procedures that extend the upper frequency limit of plane wave measurements.