Any audio data that is characterised as signal and which may include relevant information must be demodulated.
Where the demodulation process leads to intelligible audio—for example, a voice or a possible gunshot— this audio can then be assessed for relevance per BP 13.
If the audio remains unintelligible or inaudible following demodulation, or if the signal clearly only contains static or silence, it may be deleted. However, the Collector should consider still preserving the signal in case it could be rendered intelligible by future technology.
The Collector should also consider the feasibility of storing and preserving the non-demodulated signal (the ‘raw’ signal) within, or linked to, the audio data file.
Legal Framework
See section 5.2 on the importance of evidence being intelligible in order to be considered relevant.