Q: There’s been a lot of discussion recently about the desirability of using audio recording in CCTV systems. What’s the current position on this?
A: Unfortunately, nothing has yet been definitely resolved. The issue is one of liberty versus law and order, and there is no easy answer. However, a draft Code of Practice from the Information Commissioner’s Office (ICO) warns that audio recording in CCTV systems is “highly intrusive and unlikely to be justified”. Note that this document is only a draft at the moment, and it refers specifically to recording conversations between members of the public, rather than to recording audio in sensitive situations where the public wouldn’t normally be present. It does, nevertheless, emphasise the need for caution, and to discuss fully the implications and desirability of audio recording with the client.
Q: In what sorts of applications can audio recording be used?
A: Usually it’s only applied in high sensitivity areas, such as near a cash office, but it can also have other applications. It could be used near disabled facilities, for example, to enable someone who has problems but is out of camera shot to call for help. Whatever the application, audio recording can only be used to cover small, well-defined areas, usually in conjunction with a fixed camera and a directional microphone. It’s not really practical to provide audio coverage for large open spaces, such as the general areas of a shopping mall.
Q: What about signage?
A: The current ICO Code of Practice doesn’t make specific mention of signs in relation to audio recording but, depending on the application, the installation of signage to indicate that audio is being recorded as well as images should at least be considered.
Q: Are there any specific technical issues relating to recording?
A: Microphones must be selected and sited with care if the recordings are not to be swamped by background noise – suppliers should be able to give guidance. It’s also worth noting that audio recordings are of limited evidential value unless they are lip-synchronised to the CCTV images. Lip synchronisation can, however, only be achieved with images recorded at rates of 12.5 frames per second and higher. This means that a CCTV installation with audio may need considerably more storage capacity than one without, where much lower frame rates may well be acceptable.
