Which device measures the acoustic output of a transducer?

• A. Receiver
• B. Hydrophone
• C. Display
• D. Hydrometer

Answer: (B)

Measuring the acoustic output of a transducer is about capturing the actual pressure waves it emits. A hydrophone is a tiny microphone designed to detect acoustic pressure in liquids or coupling media. When placed near the transducer, it converts those pressure fluctuations into an electrical signal that can be calibrated to quantify acoustic parameters such as peak pressure, time-averaged intensity, or output power. This direct measurement is essential for verifying safety and performance, since it tells you exactly what the transducer is producing.

The other devices aren’t used for this purpose: a receiver detects echoes from tissue rather than the emitted beam, a display shows image data rather than the emitted output, and a hydrometer measures liquid properties like density, not acoustic pressure.