The Matched Acoustic Generator

The design of a swept-frequency, acoustic generator for quickly measuring the insertion power gain and bandwidth of flueric components is described and illustrated. The generator is used to produce and measure the signal incident on flueric components without being affected by reflections from them. The components are connected to the generator by transmission lines. The output of the flueric component is measured in a line of the same diameter as the input line and long enough to attenuate reflections from the far end of the line to negligible levels. The generator produces a 17.7 × 10⁻³ kilopascal (2.6 × 10⁻³ psi) acoustic signal in a 1/8 in. (0.32 cm) line over the frequency range of 200 to 5000 Hz. The maximum error in the measurement of the incident pressure signal is approximately 5 percent. More precise construction of the generator could reduce the measurement error, but the accuracy is sufficient for many engineering purposes. The swept-frequency responses and carrier-pulse responses of several flueric amplifiers are illustrated and in particular the frequency response of certain proportional amplifiers has been shown to extend to 4000 Hz.