High resolution acoustic impulse response in air with spectral extrapolation by linear prediction

We present an experimental evaluation of high-resolution acoustic impulse responses of structured objects in air obtained by a new signal processing technique. Typical acoustic transducers in air have a high Q of 20 and a narrow passband of 40 kHz around the resonance frequency of 200 kHz. First we have simply deconvolved the echo signal of an object with the transfer function of the measuring system using a standard reflector. After an adequate extraction of the spectrum of the passband, we have extrapolated it over to a wide-band spectrum from 0 Hz to 3 MHz by a factor of 75 by a linear prediction using an AR model and Levinson's recursive formula with no such a sensitivity to the prediction order as in the power spectral estimation. Resolution of the reconstructed impulse responses of structured objects in air is a sampling spacing /spl Delta/x=0.024 mm which corresponds to a sampling frequency of 6 MHz, and the range accuracy is within 5 /spl Delta/x.