Which device is most commonly used to measure sound pressure?

• A. Ultrasonic microphone
• B. Tachometer
• C. Geiger counter
• D. Sound-level meter

Answer: (D)

Measuring sound pressure relies on converting the fluctuating air pressure from a sound wave into an electrical signal and then showing it as a sound pressure level reading. The most common tool for this is a sound-level meter, which combines a microphone (to sense the pressure changes), a preamplifier, and processing electronics that output the level in decibels, often with weighting like A-weighting to reflect human hearing. This setup is standard in occupational hygiene because it gives a direct, portable, and calibrated readout of how loud the environment is.

The other devices described serve different purposes: an ultrasonic microphone is designed for frequencies above the audible range, a tachometer measures rotational speed, and a Geiger counter detects ionizing radiation.