As if to prove that not all noise-cancelling headphones are created equal, Sony has applied its biggest brains to the job and come up with what it claims are the world's first headphones that cut out 99 per cent of external noise.

Not only that, but the signal processing is the first to be done digitally, rather than by using analogue audio. The ¥49,350 (£238) MDR-NC500D 'phones go on sale in Japan only on 21 April and have three pre-programmed modes to suit various settings.

Trains, planes and aircons

Mode 'A' is for easy listening in the hi-fi hell that is an aircraft cabin (seat console adapter included). 'B' covers trains, buses and cars, while 'C' targets the background hum of domestic or office air conditioners.

On the downside, the 195g NC500Ds can't be used as passive headphones, meaning the noise-cancelling function is always on and consuming power. Still, 16 hours from the supplied li-ion battery is very respectable, as is the 10 hours that can be squeezed from a pair of alkalines.