Piezoelectric instruments

Some examples of everyday instruments that use piezoelectricity include

• Piezoelectric sensor is a device that uses the piezoelectric effect to measure pressure, acceleration, strain or force by converting them to an electrical charge.

• Geophones – convert a ground movement (displacement) and thus a mechanical vibration into voltage  - an electrical signal

• Cigarette lighter - One of the simplest and best-known uses, however, is the electric cigarette lighter: pressing the button causes a spring-loaded hammer to hit a piezoelectric crystal, producing a sufficiently high voltage electric current that flows across a small spark gap, thus heating and igniting the gas. The portable sparkers used to light gas grills or stoves work the same way, and many types of gas burners now have built-in piezo-based ignition systems. 

• A hydrophone (Greek "hydro" = "water" and "phone" = "sound") is a microphone designed to be used underwater for recording or listening to underwater sound. Most hydrophones are also based on a piezoelectric transducer that generates electricity when subjected to a pressure change. Such piezoelectric materials, or transducers can convert a sound signal into an electrical signal since sound is a pressure wave.  A hydrophone can "listen" to sound in air, but will be less sensitive due to its design as having a good acoustic impedance match to water, the denser fluid. In effect we have conversion of  acoustic energy [which is essentially mechanical whether in air or in water] to electrical energy

• A crystal microphone or piezo microphone uses the phenomenon of piezoelectricity to convert vibrations into an electrical signal. An example of this is potassium sodium tartrate, which is a piezoelectric crystal that works as a transducer, both as a microphone and as a slimline loudspeaker component.  Piezoelectric transducers are often used as contact microphones to amplify sound from acoustic musical instruments, to sense drum hits, for triggering electronic samples, and to record sound in challenging environments, such as underwater under high pressure. The saddle-mounted pickups on acoustic guitars are generally piezoelectric devices that contact the strings passing over the saddle. Again,  we have crystals being used to convert acoustic energy [which is essentially mechanical whether in air or in water] to electrical energy