n [U] sound withan ultrasonic frequency; ultrasonic waves 超声（波）
*[attrib作定语] an ultrasound scan, eg to detect abnormality in a foetus 超声波扫描检查（如可用以检查胎儿是否畸形）.
sound that is too high for humans to hear
[U and C]
a medical process using this type of sound, that produces an image of something inside your body
investigation of the liver by ultrasound
An ultrasound scan revealed that the baby was a boy.