Rock the house without waking the neighbours is the promise of a new audio beam speaker jointly developed by engineers in Singapore and China.
"The audio beam is a new concept of loudspeaker. It can focus a narrow beam of sound, just like a beam of light," Mr Zhang Ming, the project's head researcher, told reporters on today.
"Only the person within the beam area can hear the sound."
The speaker uses ultrasound, which is beyond the range of human hearing and used in medical applications such as pre-natal scans, as a carrier for audible sound.
The researchers hope to further develop the system to track a listener moving around a room.
"Because the power of the ultrasound transmitted is very low, we don't think (it) will harm people's health," Mr Zhang said.
The joint research by the Centre for Signal Processing at Singapore's Nanyang Technological University and the Institute of Acoustics at the Chinese Academy of Sciences in Beijing developed a prototype after just four months of work.
The audio beam speakers may do away with multiple speakers in stereo systems as they produce a wide band of frequencies usually handled by separate woofers and tweeters.
But the sound quality of the prototype is not yet up to the standard of conventional speakers, Mr Zhang said.
Researchers are planning to improve the technology, patent it and have a final product ready in two to three years. The idea is to have a single speaker produce multiple beams of sound.