Adjust the microphone internal gain

Aim

To adjust the gain of the 250-kHz microphone. Do this only when adjusting the gain in UltraVox XT does not give the expected results.

nFor rough gain adjustments, adjust the microphone internal gain (see below).

nFor fine-tuning the output, Adjust the microphone gain in UltraVox XT.

nSee also Experimental setup and Microphone position

Procedure (250-kHz microphone)

1.Unscrew the microphone lid (connector side) and pull out the circuit board out of the aluminium cylinder.

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2.Place the microphone at the top of the cage, pointing down to the middle of the cage.

3.Connect the microphone to the PC.

4.Start UltraVox XT, and choose Setup > Experiment Settings.

5.Click Settings for that microphone, then click the Start monitoring button.

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6.In the software, set the Gain to a low value like 20. A low value is recommended because a high software gain increases noise more than the microphone’s internal gain.

7.‘Place the microphone over the subjects. Check the waveforms on the Amplitude plot and in the spectrogram.

The vocalizations should be visualized in the spectrogram. See Eliciting vocalizations for test purposes

8.Locate the trimmer on the board. This is a small box with a tiny screw on one side.

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9.Gently turn the trimmer screw: counterclockwise If the waveforms are out of scale; clockwise if the call waveforms are too narrow.

10.Test the microphone with the actual sound source. There should always be a gap between signal peaks and the minimum and maximum values of the plot.

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11.When finished, click the Stop monitoring button and then click OK.

12.Put the board back in place and close the microphone.

13.For fine tuning, adjust the Gain value in UltraVox XT.

Repeat the procedure for the other microphones.

Notes

nThe Dodotronic Ultramic 250 is not officially supported. However, short tests carried out with UltraVox XT 4 on Dell 3680 desktop with Windows 11 version 24H2 did not reveal significant issues.

nFor 384-kHz microphones, we recommend not to adjust the internal gain. The trimmer inside the microphone only allows changes in sensitivity significantly larger than microphone-to-microphone sensitivity variation.

nTo produce ultrasound, move a key chain in front of the microphone, at a fixed distance. However, with this method you do not calibrate the microphone to the real animal’s vocalizations. See Eliciting vocalizations for test purposes

nMultiple microphones need not to have exactly the same optimal gain. For each microphone, try to find the gain that results in a clear spectrogram of calls.