Calibration method in measurements of acoustic characteristics of materials in a water filled impedance tube

A three-parameter calibration method are presented in measurements of acoustic characteristics of materials in a water filled impedance tube using transfer functions. Based on two-sensor transfer function method, three dimensionless calibration parameters are derived to calibrate the variance between the two hydrophones and the local perturbation of small structures in the tube, etc. These calibration parameters can be figured out by measuring the three transfer functions of three different but known reflection coefficients of the measurement plane in the water filled impedance tube. The acoustic characteristics of the water/air interface and a kind of underwater material are measured respectively in the water filled impedance tube. The measurement results are compared before and after using the calibration method.