Soccer hooligans could be silenced by a new sound system that neutralises chanting with a carefully timed echo.
Stadiums could use the technique to defuse abusive or racist chants, say the Dutch researchers behind it. The echoes trip up efforts to synchronise a chant, neutralising an unwelcome message without drowning out the overall roar of a crowd.
Sander van Wijngaarden, who researches human acoustics at the Netherlands Organisation for Applied Scientific Research in Delft, began working on the technique in 2004 after several Dutch soccer matches were blighted by abusive chanting.
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鈥淲e knew that people become confused if you feed their speech back with a delay,鈥� he told New 杏吧原创. 鈥淪o we wanted to try and apply it in a group context.鈥�
To chant in time a person must keep track of several different sound sources around them. 鈥淭his can be very complex because there are large numbers of people involved,鈥� van Wijngaarden explains.
Split-second delay
Along with colleagues he developed a prototype echo system and tested it on male volunteers. 鈥淭hey didn鈥檛 come from the stands of a football ground, but had an interest in football and were in the right age group,鈥� he says.
The volunteers were surrounded by loudspeakers that simulated the sound of a chanting crowd and were asked join in. However one speaker replayed the crowds chant with a short delay.
When the delay was greater than 200 milliseconds the volunteers found it too difficult to chant coherently. Increasing the delay, up to about 1 second, was even more effective. 鈥淚t was very confusing,鈥� van Wijngaarden says.
He believes the system could be effectively used in a real stadium, but admits that it would have drawbacks. 鈥淚t had to be quite loud,鈥� says he says. 鈥淲e鈥檇 hoped it could be quite soft, but the feedback echo has to be almost as loud as the chant.鈥�
Mind scrambler
Tests involving a crowd of 350 at a real stadium also suggest special hardware would be required. 鈥淵ou need more than the simple sound systems stadiums have,鈥� van Wijngaarden explains. For example, specialised microphones would need to be installed strategically around a crowd.
No soccer clubs have yet expressed an interest in the technology and van Wijngaarden says any real implementation would need to be closely monitored. 鈥淚f you frustrate an audience by making it impossible to chant, you need to be very careful how you channel their frustration,鈥� he says. 鈥淚f they stop chanting but start rioting out of frustration, then you鈥檙e worse off.鈥�
John Williams, a sociologist specialising in soccer culture at Leicester University, UK, believes some fans would only see the system as a challenge. 鈥淚 can see people taunting the censors with racist chanting just to experience the effect of having their mind scrambled,鈥� he says. 鈥淵ou have to look at taking on the problems elsewhere in society too.鈥�
Van Wijngaarden will present the results of his research at the 151st meeting of Acoustical Society of America in Rhode Island, US, in June 2006.
