| Quote: |
|
| Quote: |
|
I will do some experiments on acoustic noise canceling during my stay.
Now I am planning to cancel acoustic noise from PMC and see how the acoustic noise work and how we should place microphones.a
First, I measured the noise in microphones and its circuit.
-blue, green, red, solid lines; microphone signals
-blue, green, red, dashed lines; un-coherent noise in signals
-yellow, black, solid lines; circuit noise (signal input is open, not connected to the microphones)
We can see the acoustic signal above 1 Hz, and the circuit does not seem to limit its sensitivity. But I do not know why yellow and black is so different. I will check it tomorrow.
|
Hi, Ayaka. It would be good if you could give a little bit more detail about this plot:
- What exactly are the "signals"? Are you making a sound somehow? If so, what is producing the sound? What is it's spectrum?
- Are the blue/green/red traces from three different microphones?
- Coherence usually implies a comparison between two signals. Is something being compared in the dashed traces?
- Are the yellow and black traces from different amplifiers?
- What are the units of the Y axis?
|
Sorry for my poor explanation.
I measured this by the same way as you measured the instrumental noise of seismometers.
I put the three microphones at the same place so that the three can hear the same sound. I did not make any sounds, just put them in the lab.
The signals from microphones are all amplified by the circuit.
And I took the correlations of each signals and two others and got the noise (dashed lines) by subtracting the correlated signal from the original signal.
So,
-The signal is the acoustic sound in the lab, amplified by the circuit.
-Three lines are from three different microphones.
-Dashed lines are subtraction of coherent signal from the original.
-Yellow and black lines are from different amplifiers in the same circuit box. The circuit has 6 channels.
-I did not calibrate the signals I got by DTT since I do not know the calibration factor now. It is just the number I got from the real time system.
|