For hydrophone spectrogram (PNG and PDF) data products only, when FFT spectral data is available (icListen HF hydrophones currently):
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Audio Data Preferred (FFT spectral data fills in gaps only)
In this default option, searches for spectrogram data products will return the best combination of spectrograms sourced from .wav or .hyd audio data files and sourced from FFT spectral data files. Hydrophones produce audio data and spectrograms are best generated from the audio data. However, in some circumstances, such as low bandwidth data connections to remote hydrophones or military diversion, audio data is not available and we only receive spectral FFT data files. Spectrograms produced from those files are combined FFT data files fill in the gaps where with normal audio data sourced spectrograms to present are not available. This presents the user with the most complete coverage of data.
Audio data only
This option will cause the search to only return spectrograms sourced from audio data. This is useful if you just want the high resolution spectrograms.
.fft Spectral Data only (maybe available regardless of data diversion mode)
This option will cause the search to only return spectrograms sourced from FFT spectral data files only. This is useful when audio data is present, but is limited in bandwidth due to military diversion. FFT sourced spectrograms have less resolution than audio sourced spectrograms but often have frequency ranges from 0 to well above 44 kHz (audio data is often limited to 44 kHz sampling).
File-name mode field
Spectrograms produced from .fft spectral data files are appended with a '-FFT', and are also noted as such within the plots themselves.