Acoustic parameter estimation for design of piezoelectric telephones by the nonlinear optimization method

Abstract

Until now, no formula has been derived for computing the acoustic parameters of the transmitting and receiving systems in the actual piezoelectric telephone handset of small size and light weight. The lack of such a formula was a significant hindrance to the design of the handset. In this paper, estimation of these parameters is made possible by the application of the nonlinear optimization technique. In this optimization problem, convergence is extremely slow since there is a magnitude difference of about 1010 among the parameters. Hence, for each parameter, a hypothetical maximum and minimum are assumed so that the problem is replaced with a hypothetical conditional optimization problem. By means of the change of variables, the variable ranges of all the parameters are aligned. At the same time, the problem is transformed back to the optimization problem without constraints so that the convergence is accelerated. Since the performance function is constructed in which all the measured characteristics of the transmitting and receiving sensitivities under different measurement conditions are used as esimating information, the resultant optimization problem is of a significant size. The simulation characteristics computed based on the obtained estimation values agreed well with the measured characteristics. This implies that the estimated value derived by the present method is useful in actual design of the handset.