抄録
A new method for measuring the delay time is proposed. If the observed signal is regarded as an output signal of the delay plus minimum phase system, its delay time can be estimated by use of the Hilbert transform relationship which holds between the log magnitude and phase of the transfer function of the minimum phase system. Discussions are mainly focused on the practical case where the observed signal is band limited. A procedure for extrapolating the frequency characteristics of the signal is presented to minimize the estimation error due to the bandwidth limitation. The method is applied to the measurement of the boundary location of acoustic materials whose reflection characteristics are minimum phase. The case of non-minimum phase system is also discussed and the boundary location of a turf-covered ground is estimated. Using this result, the acoustic impedance of the turf-covered ground is computed.
