Active noise reduction headset technology helps reduce ambient noise. How does this technology work?

Noise cancellation

High School



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The student discovers the wave nature of sound waves and interference. He deduces how the noise canceling features work on modern headphones.

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Scan the QR code within the FizziQ app: 
to add this activity in FizziQ: in the "Activities" tab, press "+", then select "Scan a QR Code" 
Sample protocol for the student
1. Active noise canceling headphone technology reduces ambient noise. How does this technology work?
2. You need 3 smartphones on which the FizziQ application is installed. Two smartphones serve as a frequency generator and the third is used to measure sound.
3. In the Sound Library, select the 680 Hz sound which will produce a constant sound at that frequency. Adjusts the volume of the two laptops so that they produce sounds of approximately equal loudness.
4. Place the two portable transmitters at a distance of about two meters, and measure the amplitude of the signal by moving your third portable between the sound sources.
5. What do you see? Mark the places with the lowest sound amplitude and the places with the strongest sound frequency.
6. Bring your ear closer to these places, you can verify that the sound is indeed louder or quieter.
7. How do you explain this phenomenon? Can you predict the distance between the weakest amplitude points?
8. Can you deduce how the active noise reduction technology works?

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