Practice question · Multiple choice
Noise-cancelling headphones generate sound to make things quieter. Which principle are they exploiting, and what limits them?
Hints
- Ask what has to be true of the generated wave's phase for the sum to be zero.
- Why would a low-frequency hum be easier to cancel than a sudden clatter?
Show the answer
C. Destructive interference, whose limit is timing
Why
The wave is inverted and summed, which is superposition doing arithmetic, and it demands accurate phase, so a predictable 100 Hz hum is easy and a transient is over before the system can respond. The energy is redistributed rather than destroyed, exactly as the interference lesson requires.
Practise Oscillations and Waves
The app has 5 more questions on this lesson, and keeps your place in the course. Computer Science I is free to start.
More questions on Oscillations and Waves
- Complete the defining property of simple harmonic motion that makes pendulums good clocks.
- Select every statement that is TRUE of simple harmonic motion and waves.
- Two identical waves overlap. Sort each described situation by the kind of interference it produces.
- Two identical waves meeting exactly out of phase cancel, which means their energy has been destroyed.