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Mini-Quiz: Noise Cancellation

by Ron Kurtus (revised 18 March 2012)

Take this Mini-Quiz to check your understanding of the lesson material.

1. How is it possible that adding two sound waves results in no sound?

It really results in sound so loud that you can't hear it

It is similar to an optical illusion

It is the addition of positive and negative pressure, which then equals zero

2. Why is it so difficult to cancel out the spoken word?

It depends on what language the person is speaking

There are extremely many frequencies in such sounds

Some people refuse to shut up

3. How is vibrating a wall similar to noise cancellation with a headset?

The sound is cancelled at the source of the sound into the room

It only works if you put your ear to the wall

It reflects the noise back into the other apartment

If you got all three correct, you are on your way to becoming a Champion in Physics. If you had problems, you had better look over the material again.

Look at achieving the impossible

Resources and references

Ron Kurtus' Credentials


There are different areas for information on active noise reduction.


DARPA DSO: Defense Sciences Office sponsors research and development in the application of smart materials to active noise control problems. Defense Advanced Research Projects Agency

Noise Control and Noise Cancellation- From DARPA MTO, which sponsors research and development in the application of active noise control to air-coupled sensors and related applications


Siemens develops noise cancellation system for cars - Article from

Products and companies

NVH Technologies - A supplier of active noise cancellation and active vibration cancellation solutions

Noise Reduction Headsets from Bose

Top-rated Noise Reduction Headphones - These headsets available through range from $25 to $200

Silentium - Company provides products and solutions for the reduction of acoustic noise generated in electrical products


Physics Resources


Noise Reduction in Speech Applications by Gillian M. Davis, CRC Press (2002) $101.30 - Comprehensive introduction to modern techniques for removing or reducing background noise from a range of speech-related applications

Top-rated books on Active Noise Cancellation

Questions and comments

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