Sound ideas

From stereos that place your favourite artists in your living room to entertainment systems that turn your home into the Sydney Opera House, today’s audio technology is unrecognisable from the scratchy old gramophones of yesteryear.

However, with no one but the most diehard audiophiles now able to discern the tiny improvements in sound quality offered by the latest hi-fi systems, it seems conventional loudspeaker technology has developed about as far as it can.

With this in mind, researchers around the world are turning the science of sound on its head and developing a range of approaches to transmitting and amplifying sound that are attracting the interest of everyone from advertisers to military strategists.

In a striking development, Californian firm American Technology Corporation (ATC) has created a system that enables focused beams of high-quality sound to be precisely targeted at individuals in a crowd.

While labs such as Sony and Bell dabbled with directed audio technology in the 1960s Woody Norris, ATC’s founder and chairman, believes he has now refined the technology to the point where it is sufficiently cheap and of high enough quality to be used in a variety of exciting new applications.

Norris’ so-called HyperSonic Sound (HSS) represents a departure from traditional technology. While regular loudspeakers propagate sound using a cone that pumps back and forth and bumps against the air, HSS uses an ultrasound emitter.

Moving between 50,000 and 70,000 times a second, this emitter generates a tightly focused beam of sound audible only to those standing directly in its path. ‘Sound is made at every point along the column,’ said Norris. ‘Its directionality is unbelievable — the beam only spreads to about two degrees. You can hear it if I aim it towards you, but if I tip it slightly up in the air you will hear nothing whatsoever. I can target an individual or one or two people in a group very easily.’

As well as this directionality, one of the big attractions of the technology is its range. ‘With an ordinary loudspeaker, every time you double the distance you lose more than half the power,’ explained Norris. ‘With HSS, because the sound is being regenerated all the way along the column, it goes about 20 times further than a regular speaker before there’s any drop-off.’

He said this makes the system ideal for public address systems at large events: ‘Imagine it being used in a rock concert — people in the front and back rows would get the same level without inflicting pain on the poor guy in the front.’

Now, however, the most promising market for HSS is its use alongside digital signage in shops, where it can be used to emit sounds that can only be heard by customers standing directly in front of the relevant display.

Norris claimed the market is being driven by significant changes in the way products are advertised: ‘There’s a trend away from advertisers spending their dollars on television because there are so many channels that when a commercial comes on, a lot of people will surf. There’s a move to bring commercials closer to the audience and a resistance to making stores sound like a penny arcade.’

Norris, who numbers Wal-Mart, McDonald’s and Gap among his customers, estimates he has about 50,000 of his HSS units in operation.

In the UK, the technology has been in use at Heathrow Airport’s baggage check-in desks since late last year, where it beams information to people queuing, while sparing staff the irritation of listening to announcements all day.

Andy Phillips, an audio and acoustic engineer with Audio Nation, the Somerset-based UK distributor of HSS, said he is investigating a number of other possible UK applications, including the installation of HSS systems alongside monitors in betting shops.