Choice of base signals in speech signal analysis

Fourier series is generally considered to be one of the most basic mathematical tools of the communications engineers; when experimental support is sought for the theoretical conclusions obtained, it has the advantage of having readily available source equipment in the form of sine-wave generators. In many cases, however, due to the characteristics of the signals under study, the analysis into other base functions would result in a reduction of expression complexity and a better insight into the problem. This is demonstrated on a specific example, in which the damped-oscillatory voiced speech sounds are expressed by means of complex-exponential base functions. The method of measuring the pertinent coefficients is given; the nature of the analyzing equipment, which is also used for synthesis, is described briefly, and experimental results, including synthetically obtained approximations of the original signals, are presented. While speech signals are used to illustrate the method, the latter is applicable to other signals as well.