APPLICATION OF PARAMETRIC AND NONPARAMETRIC TECHNIQUES TO ELECTROACOUSTIC TRANSFER-FUNCTION ANALYSIS

Electroacoustic devices or systems transfer functions are usually desc ribed by means of amplitude and phase Bode plots. They are obtained fr om usually large data series of excitation and response values. Acoust ic set-up requirements vary considerably, from normal room to anechoic conditions, from complex instrumentation to simple sweeping ensembles . Filter frequency analysis, cross-spectral estimation by means of the discrete Fourier transform, time-delay spectrometry and the cepstral analysis methods are non-parametric examples. Model based techniques c an be classified as identification techniques. They usually employ a l imited set of parameters and achieve high information compression rati os and non-redundancy, flexibility and adequacy to convert to other ty pes of models. In the present paper the most important established tec hniques for electroacoustic transfer function measurement are surveyed in their principles, possibilities, instrumentation and set-up requir ements. A comparison is made with an input-output rational model based parametric technique, developed in the F.E.U.P. Practical results are reported, showing the accuracy obtained through this technique when a pplied to the measurement of a real full-range loudspeaker system. Nev ertheless some difficult aspects still persist. In our point of view, a promising new way is ahead for measurement techniques in the electro acoustic field.