ABSTRACT
The piezoelectrical transducers (PAC-A3) were sensitive in view of acceleration and had a frequency range of 20-100 kHz (resonance frequency 30 kHz). This frequency was very low compared to usual AE-trials, but it was necessary because of the high attenuation of the sound waves in concrete. Fig. 2 shows some frequency spectra of simulated AE-events produced by ultrasonic transducers. Mainly frequencies above 50 kHz are damped after distances between source and receiver of more than 1 m.
