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Amazon headphones could switch off to help you hear a police sirenReuters

Amazon is working on a pair of noise-cancelling headphones which turn off when someone says your name, or other times when you need to listen to the outside world.

Noise-cancelling headphones create silence in the wearer's ears by playing the opposite sound frequency to what's going on around you. They are particularly good at silencing the constant drones of planes and trains.

The headphones being developed by Amazon, referenced in a patent filing made public in July 2016, use this technology to block outside noise, but the company also recognises how sometimes the wearer needs to hear clearly. As such, these headphones employ a system which listens out for keywords, then switch off the noise-calling system.

Called 'suspended noise cancellation', the system can be taught to listen out for certain keywords or phrases.

For example, the wearer's name could be a keyword, or the phrase "excuse me" could be used to switch off the noise-cancelling when a fellow commuter needs to get past you on the train. Safety demonstrations on aeroplanes or an underground train announcement about delays could also be used to trigger the system.

More importantly, the headphones could help pedestrians hear emergency vehicle sirens and car horns more clearly, or help them listen out for the alert to say it's their turn to cross the road.

As with all patents, there is a major caveat here. Companies research new technologies all the time and file patents to protect their intellectual property, stopping other firms from stealing an idea. Noise-cancelling headphone likes those described by Amazon may never actually go on sale, but it's still interesting to see Amazon actively work on a type of product, headphones, which it doesn't yet sell.