| Popis: |
The mean‐square pressure distributions in the ultrasonic fields generated in water by quartz transducers of various shapes were presented on an oscilloscope screen and photographed. The beams, pulsed at an audiofrequency, were swept back and forth across a small pressure‐sensitive microphone placed at various distances from the source. The pulse envelopes were square‐law detected and amplified before presentation. All the transducers were of X‐cut quartz, excited near their resonance frequency of about 1 mc. Square pieces with circular and ring‐shaped electrodes, as well as circular and ring‐shaped pieces, were used; all were about 2 cm in diameter. Comparisons with theory were made for radial and axial mean‐square pressure distributions. From study of the axial distributions it was concluded that simple piston theory adequately describes these transducers, provided the baffles and electrodes satisfy certain geometrical conditions. It appears that 18.5° X‐cut crystals tend to vibrate over the whole expose... |
