Ultrasound

Sound above the 20 kHz ceiling of human hearing, where bats hunt and medicine sees inside the body.

Core Principles & Analysis

• Bats echolocate with calls reaching beyond 100 kHz; dogs and dolphins hear far above us.
• Medical imaging fires megahertz pulses from piezoelectric crystals and times the echoes.
• Doppler ultrasound reads blood flow from the frequency shift of moving cells.