Sound sensors work by detecting differences in air pressure and transforming them into electrical signals. Sound sensors such as microphones usually have built-in amplifiers that increase the strength of the incoming signal.
Sound sensors work by mimicking the human body process that involves the ears and signal transmission to the brain. Microphones are sound sensors that convert a sound signal into a voltage or current proportional to the detected signal. They typically have a small diaphragm made of magnets surrounded by coiled metal wire. Sound waves cause the diaphragm to vibrate, which vibrates the magnets and induces a current in the coil. The most common microphones used for music are dynamic, ribbon or condenser microphones.
Although microphones are the most recognized sound sensor, electrostatic and piezoelectric sensors are also used to detect sound in applications such as industrial, medical, robotics, and identification and tracking. These sensors can detect sound pressure waves that are not within the audible range, which makes them suitable for a wide range of tasks. For instance, high-frequency ultrasonic sound sensors are used to weld plastics, whereas low-frequency ultrasound sensors are used to inspect less dense materials, such as wood, concrete and cement. Such sensors are not affected by reflectivity, translucence or color, as is the case with light sensors.