With modern technological advancements there have in recent years been an exponential increase in audio and video evidence which can assist in investigations. CCTV and audio recording equipment can be found in businesses, bank machines, police and taxi dashboards, traffic lights and mobile phones. In many cases however, high quality video and audio recordings are not always available. This is where forensic audio analysis becomes important. We can clear up audio so it is easier to understand, so background noises are enhanced or reduced and we may also have to offer our opinion on what certain sounds or dialogue are. This relies on an understanding of phonetics and dialect and an experience of investigating sound analytically.
Noise can often be reverse engineered or 'cancelled out'. Intelligibility of speech can be enhanced by focussing equalisation or multi band compression on certain frequencies.
It may also be crucial to verify the integrity of an audio recording. This is where ENF, or Electric Network Frequency analysis comes in. All mains powered and portable recording devices are susceptible to ground hum. In the UK, power lines tend to oscillate a frequency around 50hz (60hz in the US). These slight fluctuations are unique and are recorded in a database by the national grid. We can use a band pass to isolate the 50hz hum area, plot these findings on a graph and then compare these findings to the national grid records for particular times - this can prove or disprove whether an audio recording was made at the time it was alleged to have been made. Whatever forensic audio tasks you may have, our experienced engineers will certainly be able to help.
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