麻豆传媒

Sound quality at open-air concerts can be disappointing. Now a smartphone app promises to put an end to tinny vocals

THE roar of the crowd! The thumping bass! The鈥� tinny vocals? Open-air music festivals aren鈥檛 exactly renowned for their balanced sound quality, but that could soon change, thanks to an audio-enhancing app for cellphones.

and colleagues at the Technical University of Denmark, Kongens Lyngby, have developed a system that transforms your phone into a personal concert speaker, letting high-frequency sounds like vocals, which don鈥檛 travel well over long distances, come through more clearly.

A mixing device on stage sends certain frequencies to an FM radio antenna that broadcasts the signal to phones at the gig. A simple portable radio won鈥檛 work as a receiver because sound travels around a million times slower than radio waves. So the FM signal must be delayed once it reaches the phone in order to align with sound from the stage. The phone鈥檚 GPS sensor measures how far it is from the stage, and the software calculates the necessary time delay.

The result is an augmented listening experience in which every note can be heard clearly through headphones. 鈥淭he sound is basically so loud at a concert that you still get the sound from the speakers, you feel the bass in your body,鈥� explains Larsen. 鈥淵ou just get this extra layer of sound that is very high quality.鈥�

His team ran tests last June during two performances at the Nibe music festival in Denmark, recruiting 19 random concert-goers to try out the app on Nokia N900 smartphones. 鈥淭he overall reactions were very positive,鈥� he says, with several people calling the sound 鈥渃lean鈥� and saying that it was easier to hear the vocals and guitars.

The team are now working with Danish start-up to commercialise the technology.

There are a few limitations, however. The time it takes to process the sound means that listeners can鈥檛 get closer than 60 metres to the stage speakers or the concert sound will arrive before the FM signal is played through the headset. The team expect to reduce this to 20 metres by optimising their software 鈥� most fans aren鈥檛 normally closer to the stage than this.

Another problem is that the GPS sensor in the phone can鈥檛 provide perfect location data, so users need to fine-tune the time delay manually. The team is also testing whether this can be done automatically, using the phone鈥檚 microphone to match the FM signal with sound from the stage speakers.

Atau Tanaka, a researcher in interactive music systems at Newcastle University, UK, says a system like this has 鈥渆normous potential鈥�, but Larsen鈥檚 particular implementation might not work in practice. 鈥淢ost mobiles on the market don鈥檛 have an FM radio,鈥� says Tanaka. 鈥淭his kind of application would need to migrate over to streaming audio over Wi-Fi or 3G networks.鈥�

The system could also be used at other live events. 鈥淥utdoor theatre, sports events, anything where you would like to have some audio information,鈥� suggests Larsen. 鈥淭his definitely has some artistic applications as well,鈥� he adds. There is no reason to limit the app to simply relaying what鈥檚 on stage, so a dedicated sound artist could add additional audio effects.