Angle-dependent in-situ measurements of reflection coefficients using a subtraction technique

The paper describes an improved PC-based method of measuring the complex reflection coefficient in situ for perpendicular and oblique sound incidence. From the impulse response measured in front of the surface, the direct sound is cancelled by subtraction with a previously obtained pseudo-free-field response. The frequency response of the reflection coefficient is determined by a fast Fourier transform after gating out parasitic reflections. Additionally, the signal separation is improved using digitally preemphasized pseudonoise signals.