A description is given of the time domain cepstral transformations (TDCT) method, which uses a time domain approach to calculate the cepstral signal representation. It offers explicit formulas to map a general mixed phase time sequence from original time into the cepstral domain and vice versa. The TDCT method avoids or minimizes the restrictions of the Fourier transform method. Explicit and unique time domain cepstral transformations are derived. No specific preconditioning window is required to obtain accurate complex cepstra. The results obtained demonstrate that homomorphic deconvolution by the TDCT method is a promising general approach.>

A multipath propagation system excited by a repetitive signal is described. The complete medium transfer function is considered as a parallel combination of paths having transfer functions with the same magnitude and shape but different linear phase functions. The total transfer function strongly depends on the phase assumptions and on the scaling of the component paths. Different echo (delay) structure is produced at the output for different path transfer functions. Simulation of this system with repetitive excitation shows that a slight change in the fundamental excitation frequency can cause large changes in the system output. The advantages and disadvantages of homomorphic deconvolution of multipath repetitive signals are discussed, and results of deconvolving real data (vehicle exhaust sounds) are presented.>

Subjective tests were performed to evaluate components of an FM-SCPC communications system including a syllabic compandor, a VOX circuit, and a shallow emphasis network. The subjective improvements in the signal-to-noise ratio were determined for these components separately and in combination. Tests of the syllabic compandor were conducted at four talker levels and at two values ofC/kTfor the SCPC equipment. Further listening tests were conducted to evaluate the advantage produced by (a) the VOX alone, (b) the VOX operating with the compandor, and (c) the VOX, compandor and a shallow emphasis network. Group distributions of compandor advantages are presented for use in designing SCPC systems.