CEDICT
ultrasound (sound with a frequency greater than the upper limit of human hearing)
Wiktionary
人耳所能聽到的聲波頻率在二十赫到兩萬赫之間,故稱頻率高於兩萬赫的聲波為「超聲波」。
重編國語辭典
頻率超過人耳可聽的最高頻(20000赫)的彈性波
維基詞典
My ultrasound is Tuesday.
Source: Tatoeba
I'd like you to have an ultrasound.