Final answer:
The conversion of electrical energy into acoustic energy by a crystal is known as the piezoelectric effect. It is utilized in various applications, including ultrasound imaging, where the crystal can transmit and receive sound waves.
Step-by-step explanation:
The process of a crystal converting electrical energy into acoustic energy is known as the piezoelectric effect. This phenomenon is observed when a voltage is applied across a material with piezoelectric properties, causing it to expand or contract and thus create vibrations that generate sound waves.
The crystal acts as both a transmitter and receiver of sound in applications such as ultrasound imaging. In contrast, the reverse piezoelectric effect occurs when mechanical stress applied to the crystal results in the generation of an electrical voltage.