Sound pulses, amplitude

Some of the problems often encountered during ultrasonic inspection of plane specimens are also found on cylindrical specimens. For example, problems associated with the directional characteristic of the ultrasonic transducer. Furthermore, the discontinuity influences the shape and propagation direction of a reflected pulse, causing wave mode transformation. In addition, the specimen influences the shape and amplitude of the reflected pulse by sound absorption. 

During the attenuation measurements. Transducer 1 was excited with a narrowband tone burst with center frequency 18 MHz, see Figure 1 for a schematic setup. The amplitude of the sound pressure was measured at Tranducer 2 by means of an amplitude peak detector. A reference amplitude, Are/, was measured outside the object as shown at the right hand side of Figure 1. The object was scanned in the j y-plane and for every position, (x, y), the attenuation, a x, y), was calculated as the quotient (in db) between the amplitude at Transducer 2, A[x, y), and Are/, i.e., a(x,y) = lOlogm Pulse echo measurements and preprocessing... 

Figure 6. Variation of microwave-induced sound pressure and brainstem potential amplitudes as a function of pulse width (21)...

In the second method wave pulses bounce back and forth with continually diminished amplitude. From the oscilloscope signals the sound parameters can be calculated. 

Such devices have been used for recordings of chest wall motions, apex motion, heart sounds and brachial and radial pulses [15]. This sensor has the advantages that it is non-contacting (skin is used as one side of the capacitor) and linear and has a wide frequency response. Sensor problems relate to the proper isolation of the patient from the high-amplitude AC excitation voltages, mechanical positioning of the probe and respiratory motion artifacts. 

The amplitude of the pressure pulses determines the loudness" of the sound, with large amplitude corresponding to loud sound. 

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