What is the direct mechanism by which the transducer emits ultrasound?

What is the direct mechanism by which the transducer emits ultrasound?

• A. The crystal vibrating due to alternating current causing compression and expansion
• B. The crystal vibrating due to direct current
• C. The crystal rotates
• D. The crystal converts heat into sound

Answer: (A)

Ultrasound transducers emit sound through the piezoelectric effect. When an alternating electrical signal is applied to the piezoelectric crystal, it rapidly changes shape, compressing and expanding in sync with the current. This rhythmic vibration at ultrasonic frequencies creates the pressure waves that travel into the tissue. Using direct current would hold the crystal in a static state, so no continuous vibration or sound would be produced. Rotating the crystal isn’t how these transducers generate ultrasound, and converting heat into sound isn’t the mechanism at play here. The key idea is that the alternating voltage drives the crystal to vibrate, producing the ultrasound.

Ultrasound transducers emit sound through the piezoelectric effect. When an alternating electrical signal is applied to the piezoelectric crystal, it rapidly changes shape, compressing and expanding in sync with the current. This rhythmic vibration at ultrasonic frequencies creates the pressure waves that travel into the tissue. Using direct current would hold the crystal in a static state, so no continuous vibration or sound would be produced. Rotating the crystal isn’t how these transducers generate ultrasound, and converting heat into sound isn’t the mechanism at play here. The key idea is that the alternating voltage drives the crystal to vibrate, producing the ultrasound.