This paper describes a digital processing technique for measuring the impulse response of a system. The method utilizes "complementary" codes as described by Golay in 1961 and has been employed by designers of radar, communications and other equipment. This paper discusses the implementation of the technique in a device that measures the impulse response of audio bandwidth systems. The paper begins by describing the general problem of impulse response measurement using digital methods. This leads to a "unit pulse" response sequence that completely characterizes a bandlimited, linear and time-invariant system. Next, Schroeder's (1979) method of probing the system with pseudo-random noise and correlating the result to obtain an estimate of this response is discussed. Our method is a variation on this scheme wherein the system is probed twice using sequences chosen from among the Golay codes. These codes have the remarkable property that their autocorrelation functions have complementary side-lobes. Finally, the response of a speaker/microphone pair is measured using the proposed method.

The signal environment of musical sound is a complex one with significant underlying structure. Past attempts at machine understanding of musical sound have been fraught with problems. We have been taking a new approach to the problem - using advanced signal processing algorithms as "sources of knowledge" in an Expert System developed to understand the sound. The emphasis in this paper is on the signal processing techniques. These include parametric modeling approaches to the segmentation of the sound, spectrum analysis, and harmonic set formation. We describe the problem specifics vis-à-vis signal processing and the techniques developed in progress to date to perform the analysis.