A LTHOUGH PICTURE quality has improved greatly with the development of flat-screen televisions (see article), sound has taken a dive. The problem is that TVs with slimmed-down screens have insufficient room for decent speakers to be fitted to them, either at the back or in the frame. Such televisions are therefore usually connected to an external sound system, such as a sound bar or a home-cinema system, to improve their audio quality.

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The loudspeakers of early televisions were as big as the screen, but engineers have got good at making speakers smaller and squeezing them into tighter spaces. A conventional speaker produces sound waves using an electromagnet to vibrate a cone-shaped diaphragm, but there are other ways to generate sound, including employing an actuator to vibrate a flexible panel. That raises the question, why not vibrate the TV screen itself? And this is exactly what a couple of television-makers are now doing.

Sony, of Japan, was the first to announce it had developed such a system, which it calls Acoustic Surface. It is now fitting this to some of its upmarket televisions. Acoustic Surface employs a pair of rear-mounted actuators to vibrate a screen made with organic light-emitting diodes (OLEDs). Unlike screens that employ regular inorganic LEDs as a backlight, OLEDs emit their light directly. This means OLED screens have few layers—and that, in turn, means they are easier to make flexible and are thus able to vibrate more easily.

This vibration is invisible to the viewer and, Sony says, does not affect picture quality. One beneficial consequence is that a programme’s soundtrack is broadcast directly at the viewer instead of from the side, as is the case with separate speakers. It is also possible to create stereo effects by moving the sound’s point of origin across the screen.

The other version of vibrating-screen technology now on offer is Cinematic Sound, from LG, a South Korean firm. This includes, as one of the screen’s layers, a 600-micron-thick film that works as an “exciter” to vibrate the display. It is all very snazzy. Sceptical audiophiles and Luddites will be pleased to note, though, that both sorts of sound screens can still be connected to separate audio systems, if the owner so desires.

This article appeared in the Science & technology section of the print edition under the headline "In your face"

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