Ultrasound is used by many animals that detect and some of them send out very high frequency sounds.
许多动物都用超声波来进行侦查，有些动物还能发出非常高频的声音。
2
Transducers are made from arrays of tiny piezoelectric structures that convert electrical signals into ultrasound waves by vibrating at an appropriate frequency.
换能器由阵列微压电结构组成，这种压电材料在合适频率下的振动能够将电信号转换成超声波。
3
While doctors offering the treatment are singing its praises over procedures that use radio frequency and ultrasound technologies, other are sounding a note of caution.