Final answer:
A Doppler log in the volume reverberation mode indicates the reflector's velocity.
Step-by-step explanation:
A Doppler log in the volume reverberation mode indicates the reflector's velocity. In this technique, the frequency of the echoed sound is superimposed on the broadcast frequency, producing beats. The beat frequency is directly proportional to the Doppler shift and hence the reflector's velocity. The advantage of this technique is that it allows for easy measurement of the beat frequency, which is in the audible range and can be amplified for audio feedback to the medical observer.