Question: A carotid Doppler machine uses what change in frequency or wavelength of a wave for an observer who is moving relative to the wave source?
Sentence (from "Carotid Doppler machine"): A carotid Doppler machine is a device which can be used to measure blood flow velocities within the cervical carotid arteries, as well as the vertebral arteries and sometimes the subclavian arteries by means of non-invasive ultrasonic scanning in which the Doppler effect is utilized.
Relevant evidence: Yes