Consumer advocates are calling for tougher limits on the noise of television advertisements after tests showed they are up to 50 per cent louder than the programmes they follow.
Testing commissioned by the Weekend Herald of 23 commercials showed primetime ads on TV3 were 50 per cent louder than programmes and TV One ads 20 per cent louder.
Harvey Norman and Placemakers ads and TV3 network ads such as for America's Top Model were among those singled out as especially loud.
The testing by the University of Auckland acoustic research centre showed the biggest difference to the human ear was the range between quiet and loud - ads had a much smaller sound range, giving the viewer fewer rests.
TV3 advertisements contrasted the most sharply, squashing the sound of ads into less than half the sound range of programmes.
The sound of TV One ads was squashed into about three-fifths the range of programmes.
The difference in range is deliberate, with advertising agencies using a technique called compression to make a "punchier sound".
While television networks test the maximum sound levels of ads and programmes to make sure they stay within peak limits, they do not test for compression as the acoustic research centre did for the Weekend Herald.
Unlike Australia and Britain, New Zealand does not have a regulatory body responsible for overseeing ad sound levels or a code that limits ads to the same noise levels as programmes.
Australian viewers can go to their advertising authority if their complaints are not dealt with adequately by the television network.
The UK will bring in a ban on "excessively noisy and strident" ads in July. To get around the problem of compressed sound, the UK code will test maximum loudness based on how the ad sounds to the human ear.
Green MP Sue Kedgley said the Weekend Herald testing showed New Zealand needed noise standards.
Consumer New Zealand chief executive Sue Chetwin agreed, saying: "People regularly complain about loud ads. Even though there are all these technical arguments about sound compression, the fact is [ads] are louder. "What people know is what they hear. They're not going to understand technical arguments about sound waves."
TV3 spokesman Roger Beaumont said it broadcast the ads as supplied, adding that loud and exciting shows would have loud and exciting ads.
TVNZ spokeswoman Megan Richards said the broadcaster had a policy of trying to match sound between ads and programmes - but said it was difficult to test sound compression with the network's current equipment.
Rick Osborne, chief executive of the Communication Agencies Association, the advertising industry's body, said UK-style guidelines were not warranted at this stage, and any future decision on their introduction should be left up to the Advertising Standards Authority.
TV ONE: TEN YEARS YOUNGER IN TEN DAYS
Volume - Ads played on average 20 per cent louder than the programme.
Range - Programme loudness ranged over a factor of 1:4.77.
Ad loudness ranged over a factor of 1:2.95.
TV3: CAMPBELL LIVE
Volume - Ads played on average 50 per cent louder than the programme.
Range - Programme loudness ranged over a factor of 1:4.42.
Ad loudness ranged over a factor of 1:1.72.
The range is the "loudness difference" between the background sound level and the maximum loudness of a track. The smaller the range, the louder a track will sound.