Why do people play music in public through a phone?
For many, teenagers playing tinny music to each other on public transport on their mobile phones can be intensely irritating. Why do they do it?
With mobile phones in many a teenager's pocket, the rise of sodcasting - best described as playing music through a phone in public - has created a noisy problem for a lot of commuters.
"All you can hear is 'dush, dush, dush, dush'. It's irritating. So many times I end up with a headache," says Tracey King, who has signed up to the Shhh! Scheme set up by bus company Arriva Yorkshire to stop the noise on their services.
"As teenagers, they don't seem to have the capability to think about others. I have heard older women turning round and saying 'will you turn that down?' and sometimes they will… and other times I've heard them with abuse and swearing at other people."
As mayor of London, Ken Livingstone called for the "absolute prohibition on playing music from a mobile system" as far back as in 2006. Young people can now have their zip cards - which allow them free travel in the capital - revoked for "anti-social behaviour", which includes playing loud music.
The issue has even been discussed in the House of Lords. In 2006, the Piped Music and Showing of Television Programmes Bill was presented to Parliament, calling for "the wearing of headphones by persons listening to music in the public areas of hospitals and on public transport" to be made compulsory, although it never made it into law.
So why do people do it? Is it just an act of youthful rebellion?
"I don't think it is intrinsically anti-social, what I would say is that it is a fascinating human phenomenon of marking social territory," says Dr Harry Witchel, author of You Are What You Hear.
"With young people, usually loud music corresponds very strongly to owning the space.
"They are creating a social environment which is suitable for them and their social peers. But for those not in this group - a 50-year-old woman for example - instead of confidence, she'll feel weakness and maybe even impotence as there's nothing that she can do about it."
But hasn't this always been the case? Most people who remember the 80s can remember someone with a boom box perched on one shoulder, pumping out the latest songs to anyone within earshot. Some take this tradition back even further.
"I reckon I was an early sodcaster," says the poet and broadcaster Ian McMillan.
"It was way back in the distant 1970s. As a teenager I was a big fan of the kind of music that made my mother say 'Will you turn that rubbish off?', and my dad hiss 'I wouldn't mind if it had a proper tune.'
"The fact is that I wasn't allowed to listen to [my favourite artists] in the house so I had to listen to them outside using a tape player."
But Dr Witchel says something slightly different was happening back then.
"When people went around with their ghetto blasters, you could argue that it was for the pure pleasure of the music they loved," he says.
"There is no excuse for why you would want to listen to tinny music, except if you were establishing territory. It just sounds rubbish. It must sound rubbish to them."
A group of schoolchildren on the 277 bus in Hackney, East London, don't all think that what they are doing is wrong.
"I wouldn't agree [that it was anti-social]," says one.
"The people who think it's anti-social don't really listen to this type of music."
A second agrees that the bus would be dull without a little bit of music.
"Fair enough, it might be anti-social but the bus is always quiet," she says. "You need something to listen to, right? We give you [something] to listen to."
Some youth workers argue that what the youngsters are doing is largely innocent.
"I don't think they [the sodcasters] are being selfish at all," says Dmitry Fedotov, of the Youth Association.
"I think if young people see sound as preferable to no sound then, if anything, they're going to be thinking they're doing people a favour."
And something is changing within the music industry itself. With the increase of songs being played through phones, more attention is being spent on the parts of the music that can be heard loudest though phone speakers.
"I think we're starting to see evidence that musicians and producers are thinking about the technology by which their music is listened to," says music journalist Dan Hancox, who has written extensively on the subject of sodcasting.
"It's something that has been described as treble culture.
"It is the idea that in this particular technological era, things that are transmittable on low fidelity (low quality) speakers are being heard more and more in pop music, quite a bit of R&B and hip hop - things which traditionally had a large and important bass element to them."
So, if this phenomenon is here to stay, what can be done by those who want a little bit of peace and quiet on their journey?
"Legislation is not the answer, and nor is citizen power, as anyone who has ever approached a sodcaster to ask them to stop will know all too well," wrote Julian Treasure, chairman of the Sound Agency, on his blog.
"I believe the heart of the solution is in teaching listening skills in schools. If we teach our children how to listen properly to the world - and especially to each other - they will understand the consequences of their own sound and be far more responsible in making it."