Headphones in, hoody up and head down: ask them to picture a typical teenager on the prowl on the mean streets of Dublin and most people will come up with a similar image. But why do so many teenagers seem soldered to their headphones, and could it have anything to do with something as fundamental as how the city is designed?

A new study, Reclaiming Public Space: Sound and Mobile Media Use by Teenagers, explores how young people use music and sound in public spaces in Dublin. Undertaken by researchers at Lancaster and Maynooth universities, it looks at how teenagers engage with the city centre, particularly Smithfield.

The study makes some sobering if familiar points about the area’s regeneration. In the 1990s an historic-area-rejuvenation project was established. It included “a range of public, state and business stakeholders, but only four local community representatives and no representation of local youths”. This is despite the fact that many teenagers use the space, walking through it to one of the four schools used in the study, or on their way to meet friends.

The square “has been designed to both explicitly and implicitly exclude certain activities and behaviour, particularly hanging out by teenagers”. This problem is not particular to Smithfield: most public spaces in Dublin are under threat from “marketisation, privatization, and austerity. Membership, rules, and gatekeepers increasingly regulate access to pitches in public parks. Billboards display rules that are policed by video cameras. The ubiquitous ‘no games allowed’ signs signal the need to move on rather than to hang out.”

Many of the teenagers who took part in the study consider public parks as spaces for small children and families; teenagers are “prohibited from gathering in some public city parks”, and many of those interviewed refer to being “moved on” by gardaí.

The dramatic change to Smithfield Square – officially called Smithfield Plaza, a name that refuses to stick – took place over 10 years and changed it from “a public space surrounded by wholesale food markets, derelict buildings, and low-rise public housing to a public space surrounded by semiprivate spaces of consumption and privately rented mid-rise apartments”.

It also fundamentally altered how the area sounds. The local soundscape became quieter, because of the loss of much street-level housing, traffic and the fish and fruit markets. This also reduced pedestrian traffic and “the prevalence of birds that had been attracted to a ready food supply”.

How teenagers interpret noise in the city is also different from how most adults interpret it. Focus groups went on walks through the city centre and Smithfield and were asked to record their reactions. The teenagers made little or no distinction between the natural sounds of the city – people, seagulls and buskers – and electronic and mechanical sounds: traffic and music from shops. Traffic sounds, for example, don’t particularly stand out for them but “surround the city in an appropriate soundscape”. Their impression was that a city is necessarily noisy and that noise gives the city meaning – “the louder it is, the busier and more productive”. They’d say it’s up to individuals to adapt to this.

By contrast, the redeveloped Smithfield Square, as most people who have walked through it will agree, is quiet – uncomfortably so, according to most of the young participants. This affected how they acted in the area: most of the teenagers kept to the edge of the space, away from the square’s eerily quiet centre.

“For the young participants, the quiet of Smithfield was not a city sound; it offered no information on how to behave in the space . . . A space without loud and continuous sounds is defined as not part of the city, or as having no meaning or purpose . . . Loud or ‘buzzy’ soundscapes create a larger space of protection in which the young participants feel safe, particularly if they are alone.”

A key part of the study is what the study’s authors, Linda O Keeffe and Aphra Kerr, call acoustic bubbles. Teenagers create these bubbles by listening to music on their headphones and creating an extra layer of sound over what’s already there. They may not have been involved with the design of the square, but they can now adjust how they experience it and, in a way, control it. Their reasons for trying to control it come back to that notion of safety.

According to the study’s authors, when teenagers hang out in large groups the noise they make acts like a safety net around the group. Faced with a big open space such as Smithfield, they compensate by heading for in-between spaces, such as doorways of public buildings, laneways and street corners: the relatively closed-off areas help to amplify their noise and make them feel safe. So the next time you see a gang of teenagers listening to music on a phone huddled in a doorway, they are doing nothing more sinister than trying to feel a bit more relaxed and safer in a place that feels built up against them.

The study also says that if teenagers can’t hang out in large groups, they tend to stick to their homes or bedrooms to socialise. At its most basic level, the study concludes, teenagers associate quiet or silence with danger, and try to combat this however they can.

That head-down-headphones-in stance suddenly seems a lot more vulnerable.