Life in the city can be noisy. That’s not where I live, so I find my occasionally unavoidable forays into its bowels almost unbearable.

“How can you live like this?” I asked a friend as we sat on the patio of a coffee shop on a downtown street as an ambulance screamed by.

“What do you mean?” she answered, looking at me with puzzled eyes, her coffee on it’s way to her mouth undisturbed.

The noise had been so obviously intrusive and irritating, that words failed me for a moment. I raised my arm and pointed along the busy, cacophonous street.

“All the people, you mean?” She smiled innocently and shrugged. “It’s near lunch time, I guess,” she said, and picked up her coffee for another sip.

I rested my hands on the table to steady them before I made an attempt to lift my own cup. “Don’t you find it rather…” I paused as I searched for the proper word to describe my angst. “… turbulent?” It was probably not the best description, but I still felt agitated.

The smile wavered for a moment as she tried to decipher my question. Then she sighed –or at least seemed to sigh –I couldn’t hear her soft intake of air in the din that vibrated and careened around us as if we were sitting in the middle of a traffic jam at rush hour. “You’ve been away too long, my friend,” she said, shaking her head sadly.

I attempted to return her smile, but I think my lips were quivering too much for it to become the answer she expected. “Doesn’t all the noise bother you Janet?”

She blinked her eyes slowly in reply. It might have been seductive in another setting, but here it only seemed like a rebuke. “You learn to block it out. It’s an urban adaptation…” Her face softened at my obvious discomfort. “To tell you the truth, I don’t think I even hear it anymore unless it’s so loud it scares me…”

That seemed counterproductive to me, but I didn’t say so at the time. Warning signals are surely just that: alarms that are meant to alert those in the vicinity to potential risks. They’re supposed to provoke a reaction. In my case it probably heightened my awareness of the risks of signal fatigue. Of crying wolf too often. Perhaps it also sensitized me to research that recognized this and attempted novel technological solutions: http://www.bbc.com/future/story/20170714-the-brain-hacking-sound-thats-impossible-to-ignore

The alerting signal the article discussed ‘was inspired by neuroscience research on sounds that affect the emotion-processing centres of the brain.’ It was originally used in Malawi, Africa, ‘To alert Malawi locals to HIV tests and health checks from a mobile clinic […].’

The problem there, as here, was the brain’s tendency to adapt to frequently discordant and unpleasant ambient noise –blocking it from conscious awareness, in effect. It ‘was inspired by the neuroscience research of Luc Arnal at the University of Geneva. Arnal had investigated what neural connections are activated when humans hear a sound that is particularly difficult to ignore: screaming. Scans revealed that, when we hear the characteristically rough, distressing sound of a scream, the amygdala – which processes fear reactions – is activated in our brains. “What I found is that this roughness doesn’t go through the same neural pathways used by speech,” he says.

It means that screams don’t just get our attention, they immediately prompt us to react in some way. We’re stimulated to actually do something. […] Arnal had previously suggested that this insight could be used to design better alarms and sirens that don’t just make us freeze when we hear them, but actually invoke a more constructive reaction.’

An American artist, Jake Harper, had previously recorded  the music of a local band in Malawi and edited it into a form that ‘sounds like nothing you’d recognise from a street elsewhere in the world. Strangely unlike a conventional emergency services siren, instead it is a discordant mashup of musical fragments and intermittent white noise.’

‘Harper spent months experimenting with audio software to try and come up with a noise that sounded man-made enough to distinguish it from human or animal voices in the bush, but which was also not overly harsh or distressing. Getting the balance right – appealing to the emotion-processing parts of the brain without inducing fear or shock – was tough. The results were encouraging. Harper says that on average, a mobile clinic would test 40 people per day for HIV. “During the trial we had 160 people come to get tested,” he says.’

For Arnal, ‘that succeeds in meeting the three key goals here: produce a sound that grabs people’s attention; avoid distressing them; make sure it is distinguishable from non-manmade sounds in the environment.’

‘Our understanding of how audio influences human psychology has evolved greatly in recent years, according to Annett Schirmer at the Chinese University of Hong Kong. For example, studies have shown that people’s neural activity can be co-ordinated with the help of external rhythms. This is exactly the sort of effect you would expect from, say, factory or farm labourers working in time to a song – or the effect of cohesion observed in musicians performing together.

“Music stimulation entrains certain mental processes and aligns them between individuals […]” However, she warns there is also a dark side to using music to alter behaviour.

“Shops use music to make customers stay longer or increase the likelihood that they purchase things,” she notes.’

This is exciting stuff for sure. As Arnal observes, ‘In the future, sound that provokes responses deep in our brains could be more thoughtfully designed into the built environment.’ But we humans are an adaptive lot. We quickly learn to ignore sounds that might have been initially distressing when we first heard them. Apart from the morbid curiosity aroused by it, an ambulance wailing past soon loses its relevance if there is no one nearby who needs it. And if it becomes a too frequent and unwelcome guest, surely the doors to our ears would quickly become unwilling to allow it entrance. I’m not advocating for the Luddites, though, just for an appreciation of Darwin.

Or, perhaps, for the sentiment of Oliver Wendell Holmes as he observed in one of his poems: And silence, like a poultice, comes to heal the blows of sound.