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Beware the Auto Gain Circuit!

PSI’s Dave Wood looks into why an annoying feature of most hand-held video and audio equipment – the Auto Gain Circuit – has ruined the results of many a paranormal investigation.

I’ve lost count of the number of times I’ve seen it. Be it on paranormal TV programs or be it on paranormal investigations, everyone seems to have ‘picked up’ unusual sounds from a dictaphone left alone in a room or from a video camera ‘locked off’ to record a scene.

Much excitement has resulted from the resulting anomalous noises, even described by some as ‘electronic voice phenomena’ (EVP). Tragically the over-active Auto Gain Circuit probably renders many of these ‘results’ as meaningless.

The Auto Gain Circuit was an invention of supposedly thoughtful developers. The role of the AGC is to keep a consistent level of sound: when a noise is too loud it ‘turns down’ the volume and when the environment is silent it turns the volume ‘right up’ in order to try to record something, anything!

The unfortunate by-product for paranormal investigators is that many of the sounds picked up during EVP sessions and video ‘lock offs’ are likely the result of noises which, whilst they sound close, could be from some distance away. Even the voice of an investigator on a different floor could be amplified, recorded and heralded as fantastic ‘evidence’.

Professional media recorders have, of course, found ways around these problems: most of us will have heard producers ‘counting in’ interviews, not just for timing, but also to ensure they don’t have a ‘noisy’ start to the interview.  

So what should paranormal investigators be doing to overcome this problem? Generating a constant low level of background sounds during video ‘lock offs’ may work, as might simply discounting auditory phenomena in ‘visual’ experiments. The established practice of using a white noise background during EVP sessions should also be helpful.

The Auto Gain Circuit is just one possibly confounding factor that renders much paranormal ‘evidence’ as useless. It’s worth remembering, also, that using recording equipment with moving parts (such as tape players or tape-based video recorders) also produce a lot of internal sounds which are picked up by the microphone.

The best tool in the paranormal investigator’s armoury, as ever, is rigour; studiously record the environment of any recording environment. Simply producing a piece of interesting ‘audio footage’ without due care to confounds and environment doesn’t impress the wider world – and it should not impress you either!