Patent ID: 7975548

Claim:
An electroacoustic apparatus adapted to operate in a gas filled space and from a first side of an object to be measured for making a non-contact ultrasound thickness measurement of the object to be measured or for making a non-contact ultrasound characterisation of a medium located on a second side of the object to be measured, the apparatus comprising an electroacoustic transducer means, a transceiver means coupled with the electroacoustic transducer means and adapted to excite the electroacoustic transducer means to output an acoustic signal towards the object to be measured and receive an acoustic response signal therefrom, and a signal processor adapted to process the response signal and to determine on basis of the acoustic response signal a thickness characteristic of the object to be measured, wherein the electroacoustic transducer means has a transducer-to-gas acoustic interface, the transceiver is adapted to operate the electroacoustic transducer means so as to emit into a gas filled gap between the electroacoustic transducer means and the object to be measured an acoustic broad band pulse towards the object and to receive the an acoustic resonance response signal in the acoustic response signal at a level that allows an acquisition of the resonance response signal above a predetermined signal to noise level, and the signal processor is adapted to determine the thickness characteristic of the object to be measured or to make a characterisation of a medium located on a second side of the object to be measured using a fast Fourier transformation (FFT) of the acquired resonance response signal above the predetermined signal to noise level.