There is constant noise at a specific frequency

Problem

The spectrogram shows constant, narrow-band noise. In this example, at about 70 kHz:

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Constant noise could be due to an electronic device near the microphone, or to the microphone being defective.

note  Cables and electric/electronic devices produce ultrasound. Voltage changes may occur, resulting in a change in noise levels during recording, which is also difficult to deal with. Isolate all cables and devices as much as possible.

Solution

1.First, try to know what amplitude is the noise signal. Draw a rectangle around the horizontal line, without including any call.

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2.A call definition is defined. Look at the spectrogram that appears at the bottom-right corner. Hover the mouse over the horizontal line and get a feel of the amplitude of that signal.

Take note of the maximum values you see.

3.Select the call definition and click the Remove button.

4.Draw a rectangle around a call.

5.Select the new call definition and click the Edit button. Set the Min-Amplitude parameter to a value well above the values of the noise.

6.Click Detect the calls in this recording.