Measuring an ultrasound echo.
Why does an echo take twice the travel time?
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Why does an echo take twice the travel time?
Why does an echo take twice the travel time?
Fit the probe, couplant and reflector and supply a fluid medium.
An ultrasound pulse travels from the probe to a reflector and then back. The receiver therefore measures a round trip, so the distance is half the sound speed multiplied by the delay. A boundary reflects sound when acoustic impedance changes. Removing the propagation medium stops the echo rather than making it instantaneous.
Normal-incidence pulse-echo in uniform lossless fluid. Sound speed is a chosen fluid property, not a diagnostic estimate. Z₂/Z₁ sets intensity reflection. Pulse duration 2 µs sets axial resolution. No tissue diagnosis, imaging or attenuation model; propagation is slowed by 40,000 for inspection, with a one-second pause before the next pulse.
Receive the echo from a 5 cm reflector within 3 µs of its predicted return.
Receive the reflected pulse in the correct time window.