Transmission/Technical Information

Why do adverts sound louder than the programme?

There's a common complaint from the viewing public that commercials sound too loud when compared with programmes.Why is this? To gain impact, commercial advertisers tend to "compress" the sound levels which means they lift them all up to the higher end - and this is what creates the greater impact. However, when compared against programmes which have a wider dynamic range - a wider variation in sound levels - this can cause irritation, because the two types of sound treatment don't sit very well together. Channel 4 has recognised this as a problem for viewers, and we use perceived loudness meters which give us a measure of the way the brain perceives the actual loudness of the sound. This allows us to adjust the levels of commercials and other interstitial material in accordance with Ofcom guidelines, so that they no longer cause irritation when compared with the wide majority of programme types transmitted by Channel 4. We continue to strive for an even perceived loudness through all our programming junctions on all our services.

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