Sonomicrometry is a technique of measuring the distance between piezoelectric crystals based on the speed of acoustic signals through the medium they are embedded in. Typically, the crystals will be coated with an epoxy 'lens' and placed into the material facing each other. An electrical signal sent to either crystal will be transformed into sound, which passes through the medium, eventually reaching the other crystal, which converts the sound into electricity, detected by a receiver. From the time taken for sound to move between the crystals and the speed of sound in the medium, the distance between the crystals can be calculated. Sonomicrometry is a technique of measuring the distance between piezoelectric crystals based on the speed of acoustic signals through the medium they are embedded in. Typically, the crystals will be coated with an epoxy 'lens' and placed into the material facing each other. An electrical signal sent to either crystal will be transformed into sound, which passes through the medium, eventually reaching the other crystal, which converts the sound into electricity, detected by a receiver. From the time taken for sound to move between the crystals and the speed of sound in the medium, the distance between the crystals can be calculated. Sonomicrometry was originally applied in the study of cardiac function in research animals by Dean Franklin in 1956, and was quickly adopted by biologists working in biomechanics as well as other physiological organ systems and structures (gastro-intestinal, uro-genital and musculo-skeletal). Medical device companies also use sonomicrometry to assess the physical performance, durability and longevity of devices during R&D phase of development. Sonomicrometry is currently the most prevalent method for determining muscle length changes during animal locomotion, feeding, and other biomechanical functions.