Aviation Electronics Technician 1 - Historic Naval Ships Association

If the sonar transducer is stationary in the waterand sends out a ping of 10 kHz, the particles all sendback a sound that has the same pitch. Now supposethat the transducer acquires forward motion and aping is sent out dead ahead. It is just as if thetransducer were the oncoming train, and the particleswere occupants of the car. Remember, that as thetrain came forward, the pitch of the whistle soundedhigher to the occupants of the car. In the same way,the particles “hear” a higher note and reflect thishigher note. Therefore, the sonar equipment willdetect a higher note than the one sent out. If thetransducer in this example is pointed dead astern, alower note than the one sent out will be heard.Figure 46-Doppler effect. A. One-second audio signal. B. One sine wave of the audio signal.4-7