3.10 Adding noise

This figure is a screenshot of the top half of the interactive interface.

On the left, the unfiltered data signal is shown as a noisy signal around 0 volts for 0.625 seconds, followed by a noisy signal around 1 volt for another 0.625 seconds. Below this are the ‘Audible signal with noise’ controls, which allow you to play the signal; a Zoom slider; and the ‘Noise level (V)’ slider, which goes from 0 to 1 and is set at approximately 0.1.

On the right, the probability histogram of the unfiltered signal is shown as two similar overlapping histograms: one centred around 0 and spanning approximately minus 0.8 to plus 0.8, and one centred around 1 and spanning approximately 0.2 to 1.8. Below this is the ‘Decision level (V)’ slider, which is set at the middle of its range; the detection statistics, which will be described shortly; and the ‘FIR filter width’ slider, which is set near the lower end of a scale from 2 to 200. The detection statistics are as follows.

• Data 1, Correct detections: 49.99 per cent.

• Data 0, Correct detections: 24.95 per cent.

• Data 1, False detections: 25.05 per cent.

• Data 0, False detections: 0.01 per cent.