Sound attenuation measurement system

摘要

A system determines the attenuation of sound in a media supporting acoustic pulse propogation. The system includes a pulse circuit generating a reference pulse, which is then transformed into an ultrasonic acoustic pressure signal by a transducer. The transducer projects the pressure signal against the media and receives acoustic pressure signals reflected therefrom in response to the projected signal. A delay circuit, coupled to the pulse circuit generates a delayed pulse with an adjustable delay relative to the reference pulse. The duration of the delayed pulse defines a reference frame to examine reflected acoustic pressure signals reflected from a depth in the media defined by the delay of the pulse. A frequency circuit counts the number of zero crossings in the reflected acoustic pressure signal during the interval defined by the duration of the delayed pulse and determines the mean frequency of those reflections at the depth defined by the delay. The attenuation is proportional to the slope of a line fit to an arbitrary number of mean frequencies plotted against the depths corresponding thereto.