A commercial break on TV channel Five was too loud, the advertising watchdog has ruled.
The broadcaster said it accepts the findings
A complaint was received after a commercial break during the film Groundhog Day in March.
The channel was found guilty of breaching the Advertising Standards Authority's standards code and its output made to undergo noise tests.
Five has been asked to ensure advertisement noise levels are "consistent with adjacent programming".
Tests carried out on the authority's behalf by broadcasting watchdog Ofcom showed the channel was using a technique called audio compression, resulting in "almost constant loudness".
"The film contained several scenes of quiet dialogue, some of which immediately preceded advertising breaks.
"Advertisement soundtracks featuring highly compressed sound played during these breaks appeared particularly strident," said the authority in its report on the complaint.
A spokeswoman for Five said that the station accepted the ruling.
Broadcasters must ensure compressed advertisements have their peak volume reduced prior to broadcast.