Synchronous detection of ultrasonic pulse echoes with a lock‐in amplifier can be used to obtain improved signal‐to‐noise ratio in the measurement of ultrasonic attenuation. It is our purpose to present circuitry that can be used for the generation of the necessary timing, trigger, and reference signals. In addition, a high‐speed sample and hold circuit, used to convert low‐duty‐cycle pulse echoes into the square‐wave signals needed for operation of a lock‐in amplifier, is described. The apparatus described has been used for attenuation measurements over the 10–1400‐MHz range in both single‐ and double‐ended sonic sample‐transducer configurations.

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