Physics for IGCSE & O level - Waves And Sounds (Section 3 - No. 32)
What does ultrasound refer to?
Sound waves with very low frequencies
Sound waves with frequencies above the range of human hearing
Sound waves with frequencies within the human hearing range
The study of echoes
Объяснение
Ultrasound refers to sounds with frequencies beyond the human hearing range (typically above 20 kHz).