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Q. |
Sound waves of a frequency beyond the hearing range of the human ear are referred to as ultrasonic waves or vibrations, and the term embraces all vibrational waves of frequency greater than approximately: |
A. | 20 kHz |
B. | 2 MHz |
C. | 2 kHz |
D. | 200 kHz |
Answer» A. 20 kHz |
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