Channel Grouping
Whistle and Moan Detector
Channel Grouping and Bearing Calculations
The Whistle and Moan detector can operate on one or more channels of data. It can also measure time delays between the arrival of sounds on different channels and use these to calculate bearings, and in some instances ranges to detected sounds.
Which channels the Whistle and Moan detector detects on and which channels it uses for bearing and range calculations is controlled by the channel grouping section of the options dialog.
When a data source is selected, the dialog will show a series of check boxes, one for each channel. Select the channels you want to use for detection OR bearing calculation, then to the right of each channel check box, assign the channel to a group. The group numbers themselves are not important - they just need to be different for each group.
The Whistle and Moan detector will detect sounds only on the first channel in each group.
If a sound is detected, it will then use data from other channels in the same group to measure time delays between the arrival of the signal on the different channels. The Whistle and Moan detector will do this independently for each group.
Measuring Range
If more than one group is present, then if whistles which overlap in time and frequency are detected on more than one channel group, the Whistle and Moan detector will attempt to cross the bearings measured within each channel group in order to estimate a range to the sound.
The example above was set up to work with a hydrophone array which consisted of four hydrophones arranged in two pairs. The separation of each pair was 3m and the distance between pairs was 200m. Detection and bearing calculation was conducted independently from each pair, and the bearings from the two pairs then crossed to estimate ranges.