I need some help with resonance.

C

Chris James

Freshman
Aug 27, 2015
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I have played a pure sine wave 1000hz test tone through multiple different speakers to multiple different microphones. When I analyze the recorded sound file, i now see a frequency at 1000hz 2000hz 3000hz 4000hz and so on until it dissipates. if i play a 2000hz tone i will see a 2000hz 4000hz 6000hz 8000hz etc. I am assuming that this is do to the general properties of any given speaker. I am trying to test the recording device. So how do I play a pure test tone without the use of a speaker ?

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Re: I need some help with resonance.

mackerr said:
You use a line level input to your measurement system rather than a speaker and a mic.

Mac
Click to expand...

Sorry Mac, I mean I am testing the Mic. We have three types of microphone. One is a grouping of Piezoelectric crystals, one is a standard microphone, the third is fiber optics. We are testing the accuracy of each.
 
Re: I need some help with resonance.

Then you need a known good measurement mic to compare them to. The tone with harmonics will be both the measurement signal and the reference signal.

Mac
 
Re: I need some help with resonance.

Chris James said:
I have played a pure sine wave 1000hz test tone through multiple different speakers to multiple different microphones. When I analyze the recorded sound file, i now see a frequency at 1000hz 2000hz 3000hz 4000hz and so on until it dissipates. if i play a 2000hz tone i will see a 2000hz 4000hz 6000hz 8000hz etc. I am assuming that this is do to the general properties of any given speaker. I am trying to test the recording device. So how do I play a pure test tone without the use of a speaker ?

View attachment 13179
Click to expand...
What you are seeing is harmonic distortion-not resonance. The louder you turn it up, the higher those harmonics will be. That is a function of ALL loudspeakers.
 
Re: I need some help with resonance.

Chris James said:
Sorry Mac, I mean I am testing the Mic. We have three types of microphone. One is a grouping of Piezoelectric crystals, one is a standard microphone, the third is fiber optics. We are testing the accuracy of each.
Click to expand...
As mentioned, you need to compare your microphones to a known low distortion test microphone. You also need speakers capable of inducing distortion in the microphone without distorting themselves, or after measuring the distortion of the speaker at a given level with a mic known to have little distortion at a given level, the difference in distortion would be your microphone's distortion.

Either your speaker, or the microphone and speaker together are generating about 5% distortion.
 

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Re: I need some help with resonance.

Chris James said:
Sorry Mac, I mean I am testing the Mic. We have three types of microphone. One is a grouping of Piezoelectric crystals, one is a standard microphone, the third is fiber optics. We are testing the accuracy of each.
Click to expand...

Chris, what are you trying to achieve, exactly? Compared to almost any microphone a loudspeaker is extremely high distortion. You need to get that variable accounted for before you can suggest you're learning anything about microphones.
 
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