Ms Chan bought a selection of toys and electric lanterns from shops near her Taikoo clinic. She found that they made noise to levels which could create negative effects.

In the long run, children could suffer irreversible partial deafness, she said, adding that children's hearing systems were particularly fragile.

The European Standard for handheld toys used by the Customs and Excise Department sets a noise level of 115 decibels, but Ms Chan said toys should not exceed 90.

'Kids like to put things right next to their ears. The levels should not go over 90 decibels and over 110 is just too much. If you look at industrial regulations, employers are made to start considering action such as providing headsets and isolating the source of noise at 85 decibels,' she said.

Education and awareness about the potential damage was scant in Hong Kong, she said. 'If the parents don't know, how will they keep an eye, or ear, on their babies and children?'

The Customs and Excise Department said that its sample of 10 battery-operated musical lanterns met the requirements of the peak emission sound pressure level prescribed in the European Standard for handheld toys that emit continuous sound.

Such toy lanterns are popular around the Mid-Autumn Festival, which begins today.

Lau Mei-yung, senior trade control officer of the customs department, advised parents to be cautious.

'Tips to guard against potential risks include not letting children put the lanterns close to their ears and sticking adhesive tape on to the speakers to reduce the volume,' she said.

Medical Association vice-president and paediatrician Wilson Fung Yee-leung agreed with Ms Chan that constant and continuous high levels of noise produced by toys in general could be damaging in the long run.

However, Dr Fung said that toy lanterns should not present too much concern because children were unlikely to hold them close to their ears.