Like all technological devices, loudspeakers, headphones, MEMS microphones, sonar emitters and police sirens all need to be measured and tested, both during design and production. Furthermore, products that generate any noise at all (such as motors, airplanes, wind turbines, coffee makers or HVAC) are often measured for safety or environmental impact, or are continuously monitored, listening for signature acoustic signals that indicate correct performance – or failure.
