🔍 Key Concepts

• Piezo-electric effect and how mechanical stress or sound vibrations can create a voltage in certain crystals • Difference between electrostatic effects and electromagnetic induction • How resistance in a material changes (or does not change) directly in response to sound pressure waves

💭 Think About

• When sound waves hit a material, what kind of physical change actually happens inside that material—mechanical stress, charge separation, or simple heating? • Which of the listed effects is commonly used in sonar transducers and microphones to convert sound energy into electrical signals? • Do all three listed effects directly and efficiently convert acoustic energy into an EMF, or are some of them indirect or not really used for sound-to-electric conversion?

✅ Before You Answer

• Be clear on which effect is specifically defined as producing an EMF when mechanical pressure or vibration is applied • Ask yourself if electrostatic or resistance change alone usually describe sound-to-voltage conversion in standard acoustic transducers • Confirm which principle is explicitly associated in textbooks with sonar transducers and echo sounders used in marine applications