How does mosquito repeller work and how does it produce sound without speakers?

Replies

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  Abhishek Rawal

  Transistors are used to amplify the signals.The output of Amplifier is given to buzzer & it produces ultrasonic soundwaves.
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  [Prototype]

  Human ears are only sensitive to the sound range of 20 hz to 20 Khz. Anything above or below is not audible to us. No speakers doesn't means no sound. Every frequency produces a sound. You're surrounded immense "noise" around you.
  
  I am not quite sure about the mosquito thing but its seems that those repellent produce a high frequency signal which might not be liked by the mosquito, however, being outside our audible range, we can't hear anything while it might be as irritating as someone scratching a board for mosquitoes. This is just a wild guess, I don't exactly know if this is the exact case.
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  lal

  Well, if your mosquito repller is making sound and you can hear it, then it is probably a fake. As prototype said above, those devices are meant to produce ultrasonic waves beyond the audible range of humans. Usually, piezo electric crsytals are made use of to produce ultrasonic waves. And these waves won't be detected by human ear.
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  aakash.kaasina

  Abhishek Rawal

  Transistors are used to amplify the signals.The output of Amplifier is given to buzzer & it produces ultrasonic soundwaves.

  what i heard is like they aren't that much useful....dont know if it is true or not