How much can ‘enhancing’ improve the clarity of indistinct forensic audio?

Indistinct forensic audio is commonly ‘enhanced’ to assist the jury in making out its content.

The reasoning is: though ‘enhancing’ rarely if ever makes unintelligible audio intelligible, it might make it a little clearer, and if it doesn’t, well, there’s no harm done. But that’s not quite right, as a recent article in The Conversation shows via a dramatic demonstration.

Here’s the example used in the article

That audio is important evidence in a murder case. To see how enhancing can make it clearer – go and read the article! Then come back here for some further reading. Questions? Don’t hesitate to contact me.

‘Enhancing’ forensic audio: false beliefs and their effect in criminal trials

Indistinct covert recordings admitted as evidence in criminal trials are routinely ‘enhanced’ to assist a jury in making out their contents. But just what is ‘enhancing’, and how effective is it? This paper uses two short experiments to demonstrate that a subjective impression that ‘enhancing’ has made the audio ‘clearer’ does not necessarily indicate there has been an objective improvement in intelligibility. It then outlines, in a non-technical manner, the capabilities and limitations of various ‘enhancing’ techniques, and discusses implications in relation to current legal practices around the admission and use of ‘enhanced’ audio in Australian criminal trials. Finally, it recommends that ‘enhanced’ versions of forensic recordings should only be admitted on the basis of objective evidence of the extent to which they have genuinely improved the intelligibility of the specific audio being used, noting that such evidence is easy to obtain and provide. Link for those WITH access to a university library. Link for those WITHOUT access to a university library.

‘Enhancing’ forensic audio: what if all that really gets enhanced is the credibility of a misleading transcript?

Many jurisdictions around the world allow an ‘enhanced’ version of indistinct audio to be admitted, along with a transcript, to assist the trier of fact in understanding the content of forensic record- ings. Typically, ultimate evaluation of the effect of the ‘enhancing’ relies simply on the jury or other listeners’ impression as to whether the audio sounds ‘clearer’ than the original. A recent article reported results of two experiments showing that listeners’ subjective impressions give a surprisingly unreliable indication of the objective effects of ‘enhancing’. The current article reports a new experiment that adds weight and detail to previous demon- strations that enhancing can make audio ‘sound clearer’ without making it more reliably intelligible. It further demonstrates how ‘enhancing’ can interact with priming to make phrases suggested by a transcript seem more plausible than they do in the original, even when the suggestion is unreliable and misleading. It is recommended that courts should insist on far better regulation of the use of ‘enhanced’ audio. Link for those WITH access to a university library. Link for those WITOUT access to a university library.

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