Bin the headphones: sound zones tailor your own audio

FINDING a way for all the passengers in a car to listen to their own audio without the need for headphones has been a goal of car manufacturers for decades.

Now scientists have positioned microphones, speakers and filters to create personalised sound zones (PSZS) in a car – pockets of space where sound from a set of speakers is audible.

Outside this small region, it cannot be heard. Scientists were already able to form a PSZ, but unable to move it to follow a person if they moved the seat forwards or backwards.

The French team created a new algorithm specifically to tackle this tissue, which manipulates the sound waves to create “bright” and “dark” zones throughout a cabin.

“This should eventually allow each passenger to listen to his or her own audio programme without disturbing others and without using headphones,” said study author Lucas Vindrola from the University of Le Mans.

“Loudspeakers are placed in the headrests, and specific filters for each transducer are calculated to reproduce an audio signal that retains good quality in the zone under consideration and is strongly attenuated in other zones.”

The researchers found that if a bright zone is created around the head of the driver, the person sitting in the passenger seat will hear it 30 decibels quieter.

This is roughly equivalent to the difference between having a normal conversation at home and whispering.

Dr Vindrola said that the key is having enough microphones placed around the car to detect how many people are in the car and where they are sitting.

“The price to pay is to have control microphones in the passenger compartment, so that the algorithm can work.

“The results remained interesting

‘This should allow his or her own programme without disturbing others and without using headphones’

even when the number of control microphones was reduced.”

But PSZ only works for a limited range of frequencies.

Sounds between 100 and 1,000 hertz (Hz), a range that corresponds from bass notes to intelligible human speech, work in the prototype technique, but nothing lower or higher in pitch. The experts hope to expand the range up to 10,000 Hz, the highest note on a piano. The findings are in