The curious sound of the void

There’s a river here, but not the kind of watery soundscape that you might have expected.

On an ordinary Tuesday, I awoke at 6:15am (to the immense surprise of my dog). I had a plan: to go down to the River Thames at Millennium Bridge to see what it sounded like in the early morning. It was late September and Olivia Colman just had won a Primetime Emmy for her performance in The Crown.

What would you expect to hear above the Thames at 7am? Not a lot of people, probably. Perhaps some boats and their engines, the splashing of water, seagulls, and some morning joggers. Perhaps a kind of marine-adjacent environment: a corridor of watery peace, where you can stand suspended between the City and the sky.

There were definitely people—many of them running, others holding early-morning conversations and phone calls. There was a train arriving at Blackfriars after 3 minutes, a plane overhead after 4 minutes, even a motorcycle in the distance around 7’15″.

But there weren’t a lot of, well, water-based sounds. A boat did pass underneath the bridge at 6’20”, but its sound was mostly engine—far from the quiet lap of the small rowing boat at the very opening of Dickens’ Our Mutual Friend, for example.

In these times of ours, though concerning the exact year there is no need to be precise, a boat of dirty and disreputable appearance, with two figures in it, floated on the Thames, between Southwark bridge which is of iron, and London Bridge which is of stone, as an autumn evening was closing in.

The figures in this boat were those of a strong man with ragged grizzled hair and a sun-browned face, and a dark girl of nineteen or twenty, sufficiently like him to be recognizable as his daughter. The girl rowed, pulling a pair of sculls very easily; the man, with the rudder-lines slack in his hands, and his hands loose in his waistband, kept an eager look out. He had no net, hook, or line, and he could not be a fisherman; his boat had no cushion for a sitter, no paint, no inscription, no appliance beyond a rusty boathook and a coil of rope, and he could not be a waterman; his boat was too crazy and too small to take in cargo for delivery, and he could not be a lighterman or river-carrier; there was no clue to what he looked for, but he looked for something, with a most intent and searching gaze. The tide, which had turned an hour before, was running down, and his eyes watched every little race and eddy in its broad sweep, as the boat made slight head-way against it, or drove stern foremost before it, according as he directed his daughter by a movement of his head.
Dickens, Our Mutual Friend, 1864-5

This Victorian river soundscape is virtually unrecognisable today, at least between Southwark Bridge and London Bridge. You can definitely hear the occasional seagull if you listen hard enough, but they have a hard time competing with the roar of early-morning traffic. It’s… Well, not quite a sonic void, but the natural soundscape is hard to distinguish, when it’s there at all.

Here’s a spectral frequency display of the whole recording, with the left channel above and the right channel below. The display is colourised by volume, from purple (quiet) to yellow (loud).

This looks like a noisy environment, particularly at lower frequencies, but that’s only true to an extent. Humans are excellent at picking out individual events from background noise, and there’s always a bit of low-frequency rumble in any field recording, which usually seems more noticeable in a frequency display than it sounds to our ears.

Nor is the Thames an actual wildlife void—far from it. Ever since being declared “biologically dead” in 1957, a massive effort from conservation professionals and volunteers has brought back seahorses, seals, saltmarshes, reeds and seagrass, lowered plastic pollution and other chemical contaminants, resurfaced tributaries and naturalised riverbanks, although 70% of the bank is still concrete according to the Thames Estuary Partnership.

Blackfriars Bridge: not a saltmarsh

But that conservation work has taken place mostly outisde of central London. Which makes sense: the Thames is 215 miles long, of which only 68 miles are tidal, and perhaps about 20 miles are in the inner two London metropolitan zones. Rewilding the banks of the Thames in central London would be outrageously difficult and expensive per unit of ecological benefit. And it’s not like cenral London is deprived for infrastructure, or even ecological restoration: the Thames Tideway Scheme, projected to open in 2025, will capture almost all of the raw sewage and rainwater that currently overflows into the estuary after heavy rains. Thames Water says they’re spending £4.9 billion on it.

Despite all of those caveats, though, this part of the Thames doesn’t sound like a river to me. I went back again, a couple of months later and at a more reasonable time of day, to stand on the same spot and hear what I could hear.

Even without birds or waves, it’s an enjoyable soundscape: active without being stressful, and with a wide scope, suspended right in the middle of the most built-up part of London. I guess you could call it the sonic equivalent of a great view. The bells on each side of the river, chiming out 11 o’clock a few seconds apart from each other, illustrate how you can hear things without being in them.

That building is uncannily tall, but at least it’s far away

Ecologically, though, this central section of the Thames sounds kind of barren to me. Not totally desolate; just a small sense that I was expecting to hear something that isn’t here, as if—to be blunt—a dry riverbed wouldn’t sound that different. It felt like a microcosm of a climate dystopia, where water features are there to be bridged, concrete-sided, and traversed on boats backed by American venture capitalists. Again, that says nothing of what’s happening under the water, which by all accounts is a lot compared to what it used to be. But at this point, suspended 10-15 metres above the central London Thames, it sounds more like a canal than a river. Maybe, with a renewed focus on natural flood defences and habitat growth, that will soon change. º