Sound Wave, Microphone and Electromagnetic Induction

In summary, Bobby said that the frequency of the sound wave is reflected in the frequency of the induced current and the amplitude of the sound wave is reflected in the amplitude of the induced emf.
  • #1
wlng81
6
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Dear all, I have encountered an issue in understanding how microphone works and I hope you guys can assist.

There are two scenarios involved.
In the first scenario, there is tuning fork and a microphone. The microphone contains a small disc attached to a magnet and a fixed coil. (Please refer to here: http://www.flickr.com/photos/11353862@N02/10851144236/)
It is mentioned when the tuning fork vibrates, an alternating induced emf is induced in the coil.

In the second scenario, the tuning fork is replaced a source that produces a sound of greater loudness but the same pitch.

The question is: How will the amplitude of the induced emf change?

I had thought the magnitude induced emf should remain the same since the pitch (hence frequency -> rate of change of magnetic flux) was the same. But I also came across some audio websites saying the amplitude induced emf would increase.
As a result, I am utterly confused now...:confused:
 
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  • #2
Remember that the acoustic waves that propagate from the source (tuning fork) to the detector (microphone) are pressure waves. When they strike that disc they push and pull the magnet, which induces the current in the coil.

When the tuning fork is replaced with a louder source, the acoustic pressure waves will be (louder) stronger and so will push and pull that mechanism in the microphone with a greater force than the tuning fork did. So, the alternating current in the coil will be the same frequency, and a greater amplitude.
 
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  • #3
Hi Bobby, can I say that the frequency of the sound wave is reflected in the frequency of the induced current and the amplitude of the sound wave is reflected in the amplitude of the induced emf?
 
  • #4
Yes and yes.
 
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  • #5
At least ideally. That's why some microphones are better (and more expensive) than others. :wink:
 
  • #6
jtbell said:
At least ideally. That's why some microphones are better (and more expensive) than others. :wink:

Out of curiosity, what are the factors that separate a good mic from a lousy one?
 

1. What is a sound wave?

A sound wave is a type of mechanical wave that is created by a vibrating object causing molecules in a medium (such as air, water, or solid) to vibrate and transmit energy. This energy is detected by our ears as sound.

2. How does a microphone work?

A microphone is a device that converts sound waves into electrical signals. It has a diaphragm that vibrates in response to sound waves and converts these vibrations into electrical signals through a process called electromechanical transduction.

3. What is electromagnetic induction?

Electromagnetic induction is the process of generating an electric current by moving a conductor (such as a wire) through a magnetic field or by changing the magnetic field around a stationary conductor. This phenomenon is the basis for the function of generators, transformers, and other electrical devices.

4. How do sound waves and electromagnetic induction relate?

Sound waves and electromagnetic induction are both forms of energy that can be transmitted through a medium. While sound waves are mechanical waves that require a medium to travel, electromagnetic waves do not require a medium and can travel through a vacuum.

5. What are some practical applications of electromagnetic induction?

Electromagnetic induction has many practical applications, including power generation in generators, data storage in hard drives, and wireless charging in devices such as smartphones and electric toothbrushes. It is also used in various industrial processes such as metal detection and welding.

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