How does sound intensity affect the current produced by a mic?

In summary, the conversation discusses measuring sound using a diaphragm microphone and how the sound intensity changes at different distances from the speaker. The microphone works by converting sound waves into electrical signals through the movement of a coil in a magnetic field. The sound intensity decreases as distance from the speaker increases due to the spreading out of sound energy. The output from the microphone is proportional to the incident sound level. The greater the amplitude of motion of the coil, the larger the induced current. This applies to all designs of microphones.
  • #1
Daniel2244
125
5
I measure sound (dB) from a speaker at 0cm and 100cm using a diaphragm microphone.
0cm-100dB, 100cm-30dB
diaphragm microphone cinsists of a diaphram, coil and a permanent magnet. the coil is attached to the diaphragm, when a sound wave hits the diaphragm it causes to move back and forth which also causes the coil to move back and forth. This coild moved along a pernmanent maget which produced a magnetic flied, as the coil cuts the magnetic field a current is induced which travels to an amplifier.

So at 0cm the sound intensisty (100dB) is larger than the sound in tensity at 100cm (30dB) away from the speaker becuase the sound waves have less distance to travel therefore losing less energy? Additionally, becuase the sound is larger it causes the diaphragm to fluctuate faster, moving the coil through the magnetic field more which inducing a larger current than it would at 100cm away? (Not sure if my thinking is correct :/)
 
Physics news on Phys.org
  • #2
Daniel2244 said:
So at 0cm the sound intensisty (100dB) is larger than the sound in tensity at 100cm (30dB) away from the speaker becuase the sound waves have less distance to travel therefore losing less energy?
Air is not a particularly lossy medium to sound waves - as can be experienced when you hear someone whispering down a speaking tube in a Science Park. The sound energy is not absorbed significantly by the air. The main reason for the sound level to drop with distance is that the sound spreads out over an ever increasing area and, hence, the sound energy flux that is intercepted by a microphone gets smaller. Over large distances in open space (3D space) the sound energy flux follows the inverse square law in the same way that light, radio waves and gravity does. The ISL falls down when you get close to the source. A loudspeaker is not a point source and you need to be a few wavelengths away, at least, for the ISL to be followed closely. Your experiment is very 'near field' and you cannot predict easily the sound levels so close to the speaker.
The output from the microphone is pretty well proportional to the level of the incident sound.
 
Last edited:
  • Like
Likes berkeman and Daniel2244
  • #3
sophiecentaur said:
Air is not a particularly lossy medium to sound waves - as can be experienced when you hear someone whispering down a speaking tube in a Science Park. The sound energy is not absorbed significantly but the air. The main reason for the sound level to drop with distance is that the sound spreads out over an ever increasing area and, hence, the sound energy flux that is intercepted by a microphone gets smaller. Over large distances in open space (3D space) the sound energy flux follows the inverse square law in the same way that light, radio waves and gravity does. The ISL falls down when you get close to the source. A loudspeaker is not a point source and you need to be a few wavelengths away, at least, for the ISL to be followed closely. Your experiment is very 'near field' and you cannot predict easily the sound levels so close to the speaker.
The output from the microphone is pretty well proportional to the level of the incident sound.
Thanks, now I understand why the sound intesisty dropped. However, do you know if a high sound intensisty increases the movement of the coil through the magnetic field producing a larger current?
 
  • #4
Daniel2244 said:
Thanks, now I understand why the sound intesisty dropped. However, do you know if a high sound intensisty increases the movement of the coil through the magnetic field producing a larger current?
I already said that the output of the microphone is proportional to the incident level. The greater the amplitude of motion (and hence the average speed) of a coil through a magnetic field, the greater will be the induced emf, which will cause more current to flow through the amplifier input stage.
There are many different designs of microphone but they all (if they are any good!) follow this rule. A half decent microphone needs to have a linear response and not limit its output at high sound levels.
 
  • Like
Likes Daniel2244

1. How does the distance from the sound source affect the current produced by a mic?

The sound intensity decreases as the distance from the sound source increases. As a result, the current produced by the mic will also decrease. This is because the sound waves have less energy and therefore, less impact on the mic's diaphragm.

2. Does the type of material surrounding the sound source affect the current produced by a mic?

Yes, the type of material surrounding the sound source can affect the current produced by a mic. Materials that absorb sound, such as foam or fabric, can reduce the sound intensity and therefore, decrease the current produced by the mic. On the other hand, hard and reflective materials can increase the sound intensity and the current produced by the mic.

3. How does the frequency of the sound wave affect the current produced by a mic?

The frequency of the sound wave does not directly affect the current produced by a mic. However, the frequency can impact the sound intensity, which in turn can affect the current produced by the mic. High frequency sounds have a greater impact on the mic's diaphragm and therefore, can produce a higher current compared to low frequency sounds.

4. Can the sensitivity of the mic affect the current produced?

Yes, the sensitivity of the mic can affect the current produced. A mic with higher sensitivity will produce a stronger current for the same sound intensity compared to a mic with lower sensitivity. This is because the diaphragm of a more sensitive mic is more responsive to sound waves and can generate a larger current.

5. Does the direction of the sound wave affect the current produced by a mic?

Yes, the direction of the sound wave can affect the current produced by a mic. When the sound wave is perpendicular to the diaphragm of the mic, it will produce the strongest current. However, when the sound wave is coming from an angle, the current produced will be weaker. This is because the diaphragm is not directly in the path of the sound wave and therefore, receives less energy.

Similar threads

Replies
4
Views
3K
Replies
8
Views
10K
  • Electrical Engineering
Replies
5
Views
3K
Replies
64
Views
5K
Replies
5
Views
5K
Replies
1
Views
10K
Back
Top