Why do I find silence unbearable?

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1:09That's the doors closing. I'm on my own in an anechoic chamber. So this is a room designed to have absolutely no noise. And they've just turned the lights out. So, this is proper sensory deprivation.

1:34I'm Marnie Chesterton. You're listening to CrowdScience from the BBC World Service, which is about this.

1:45Silence. My quest this week is to find a little bit of peace and quiet. Ideally, absolute silence. And you'll be hearing more. or should that be hearing less from that anechoic chamber later on? But of course, the reason for any crowd science adventure is always the curiosity of a listener. So let's start there. I'm Ziqi. I'm from Shanxi, China. I'm now living in Singapore for more than two years now. My question is, why do we sometimes find silence so unbearable? so you find silence uncomfortable usually at home when I'm at home alone I tend to leave the tv on just to have a little bit of background noise and the reason why I raise this question is that I figure out not just me but my partner as well so our hypothesis is that actually maybe in the nature.

2:51Silence can be a sign of danger so that we try to avoid this. Okay I love that you and your partner have a hypothesis. Yeah. This is key crowd science science listeners. Yeah we are old listeners. And when you notice silence that you don't like is that only in your home or do you dislike silence in other places too? That's a very good question because for certain places like library, silence is actually preferred because like in that kind of social setting, silence is like a common rule that everybody needs to adhere to. But other than that, I don't think there are any other places that I find silence very enjoyable.

3:44I wonder because often when people talk about uncomfortable silence, they mean the silence that happens in a conversation when you're with someone else and you run out of things to say. But it sounds like your dislike of silence is about being alone, right? Yeah, I think so.

4:07So Zici doesn't like silence, particularly when she's at home alone. And she's even got a theory that silence is a sign of danger because it's so unusual in the natural world. But what do we actually mean by silence? Is it no noise at all? Or just relative quiet, a lack of talking or traffic? And is it something we can actually quantify? So you're here in our acoustics laboratories and we have measurement equipment which will go below the threshold of hearing. Trevor Cox is Professor of Acoustic Engineering at Salford University in the UK. He's been all over the world recording sound and silence.

4:51We're sitting in what's called a listening room, where Trevor and his team test the sounds of different devices. Behind us, the walls are lined with what look like massive bookshelves. They're made of MDF, and they're there to break up the reflections from sound waves. Sound is measured in decibels. For a young adult with normal hearing, the threshold of what we can hear is zero decibels, or dB for short. Annoyingly, that threshold gets higher as we age. You can record silence with our special microphones, but generally most equipment doesn't do it. We've got microphones in front of us to record this.

5:32They will never record that quiet, because why would they? Because they're here for recording voices for podcasts. but in our labs we have very special low noise mics because we work on really low noise systems. I can think of projects like we were measuring the noise from stoma bag rustling and that's about really quite quiet sounds but people can find quite disturbing. Stoma bags, also breast pumps. There's all sorts of unusual things that when you think about it need Trevor's team to take measurements because users don't want a sound out of them. But can you measure a silence too? It's actually impossible to measure.

6:08Guinness has a world record for the quietest place in the world. It's an anechoic chamber. That's the chamber I was in at the start of the programme, designed to deaden any sound. If I remember right, it's about minus 25 decibels A-weighted. We call that DBA. But the actual record is actually for how quiet can you measure. Silence only really happens truly when there's no sound waves and there's always motion of air molecules going on creating what's called thermal noise. Air molecules, when they're warm, they're moving around. They're bashing on your eardrum. They're bashing on the microphone.

6:42They're creating a little bit of noise. If you want to get rid of that, you need to go to absolute zero. That's zero degrees Kelvin, so minus 273 degrees Celsius, the temperature at which molecules stop moving. What's going on in our heads when we hear silence? Can you talk me through the sound that we can't hear entering our brains? If there's nothing coming in from outside, your brain will turn up the volume effectively to try and pick some things out. And then it might amplify just basically neurons firing spontaneously at random on your auditory nerve. And that's things like tinnitus. If you have sort of ringing in the ears, that's the kind of effects you're hearing there.

7:23So you don't always hear silence. you might hear the stuff but it's usually your internal body stuff if you're hearing anything okay that makes it sound like silence isn't good for us it makes it sound like we hear sound and when we don't hear sounds the hearing feedbacks go a bit wonky well potentially I mean I think though it's been fairly unusual to find pure silence there's normally something there. I mean we're in this room here which is a specialist test chamber. This isn't completely silent if you were to actually measure it but actually I think at the moment we're probably all thinking it's an incredibly silent room.

8:01There is a little sort of room tone going on in the background because it's not as quiet as say an anechoic chamber. But also when people are looking for silence they're often just looking for natural sound so they're not looking for complete absence. So it's impossible to find complete and total silence because you'll always be hearing something whether that's the noises of your own bodily functions or the molecules in the air. And total silence probably isn't what anyone wants. I'm off to find a socially acceptable silence instead. So I've come to Senate House Library at the University of London and I'm thinking about our listener Zichi and how she said that the type of silence that you get in a library is a silence that she'd feel was bearable.

8:56And because you're silent, but maybe you're not in solitude, and certainly I'm not here, I'm surrounded by students busily cramming away for exams.

9:11But when I get my ear in, actually it's not so silent. I can hear rustling of bombs on seats, I can hear the wind whistling, I can hear coughs and tapping of keyboards. So it doesn't feel like an absolute silence. It doesn't feel like an unnerving silence either. So maybe silence is about where you are, but also who you're with.

9:51We were interested in particular in how do we detect danger from the behaviour of others surrounding us. Meet Marta Moita. She's a neuroscientist at the Champalamo Foundation in Lisbon, Portugal. Her lab researches the mechanisms of defensive behaviour in the nervous system. So she's interested in how animals tell each other that there's a threat in their environment. and she devised an experiment with rats that may have the answer to Zichi's question. Remember, Zichi thought that maybe she doesn't like silence because it's unnatural and a sign of danger. So we thought, OK, we have to have one animal that is threatened or perceives the situation as a threatening situation and is therefore in distress.

10:45So there's a rat that we trained such that it will now respond to a certain circumstance or cue as this is a threat. And it will display defensive behaviours. And then you have the cage mate, which is the other rat that lives with it all the time. And it's just witnessing this animal that was threatened. Marta mentioned defensive behaviours. When animals, including humans, face a threat, their responses are to run or to fight or to freeze. Marta trained her first rat to fear a sound, a beep. So when she played the sound, the rat would freeze. So far, so logical. More of a mystery was the effect on a second rat, one without the training.

11:34What we found was the cage mate would also freeze. even though it had never been exposed to that sound as a threat before. And the interesting thing then is you do something to one rat, other rat copies it, what's the mechanism? Yes, so then we were thinking, okay, so what is the information that the observer is using to decide that this is a dangerous situation and therefore I'm going to freeze also? and so we first thought you know maybe it's vision it's for us as visual animals it's the most intuitive thing okay so we did the exact same experiment but now in the dark so we have a demonstrator rat that start freezing upon upon a sound and we have the observer that still froze even though the experiment was made in complete darkness so we felt okay so it's not that they're observing through vision the other rat.

12:37Then we thought, OK, it could be pheromones. Pheromones are chemical signals that animals use to communicate, and rats need to touch each other to smell them. So Marta separated the rats, but still, the observer rat froze whenever its rat friend did. How was this fear being passed on? By the time I go home and I'm really like puzzled and I start talking with my husband, who is an artist, about my frustration with this experiment. And he's like, well, but it's obvious. And like, I mean, what do you mean it's obvious? Like, it must be silence. And I was really puzzled. I didn't really even understand what he meant by it.

13:29And he was like, OK, I'm going to show you a documentary. Marta's husband had been watching a documentary for an artwork he was creating. It was about the Portuguese army's colonial campaign in Africa, in the jungle. They knew that the animals would fall silent when they entered the jungle, and silence is a giveaway. So the army recorded the sounds of normal jungle wildlife and played that from loudspeakers. They had created this kind of sonic camouflage. So I watched this and I'm like, oh wow, we just have to replicate the Portuguese military tactics in the lab and see if for rats, this is also what they're doing.

14:16Marta's group recorded the sound of the rats going about their normal rat business, rustling their bedding, and watched the response when that soundtrack was switched on and off. And, sure enough, Marta's husband was right. The absence of those little rustling noises was the cue for danger. Is it likely that other animals react to silence in the same way? I mean, could this be an explanation of Zichi's dislike of silence? I would say this is very likely. So one of the reasons why we study defensive responses is because most animals respond in similar ways to threats. And we believe that's because the number of solutions you have is limited.

15:06So then the principles that govern these reactions are going to be very similar across very, very distant animals. So, Marta's research shows that our listeners, Ichi, may be right. Silence can spell danger. When an animal freezes out of fear, the silence coming from it speaks volumes. Just like alarm calls, it's a form of communication, a way of telling others in your group to be on their guard. But that's rats, and rats aren't people. I've heard so many stories of people craving peace, ground down by unwanted noise. You know what I've not heard anyone say? This city could use more yelling, traffic noise and sirens.

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17:00You're listening to CrowdScience from the BBC World Service. I'm Marnie Chesterton. We're searching for silence and why our listeners Ichi finds it so intolerable. We've heard how it can be a cue for danger in animals, but not everyone feels the same way. We were and we are very interested in how people perceive silence and what the beneficial effects of silence are or could be. Eric Pfeiffer has been researching the positive effects of silence for more than 10 years. He's a professor of aesthetics and communication at the Catholic University of Applied Sciences in Freiburg, Germany. And he's done a series of studies with participants looking at their response to silence in different contexts.

17:50It's always the silence as the core part of the study, but the framework is different in that the setting is outdoors or indoors or that it's alone or as part of a group. And what did your research reveal about the participants' experience of silence? Throughout all our silence studies, the participants judged or felt significantly more relaxed after the silence than prior to the silence. There was less arousal, emotional arousal. They hardly felt boredom during the silence. And what was very impressive was that it had a huge effect on the rumination, the negative form of circulation about past or future things in our lives.

18:42Rumination is dwelling on thoughts, usually negative ones. You might imagine that if you asked a group of participants, even a healthy group that chose to take part, like this lot, to sit in silence for six and a half minutes, they'd have more time to repeat bad scenarios in their heads, that there would be more rumination. But no, says Eric. Instead of this, they felt they were much more present in the here and now, in the current moment. How much do you think your results might have been influenced by the fact that your study group were people that chose to take part? And they may actually enjoy studying in silence.

19:25Absolutely. But I still do believe that some weren't that sure. But they said, well, I've got problems and I always feel like whenever I'm in silence, I'm confronted with my thoughts and I don't really like that. But the possibility to receive silence, to receive a silent condition framed by a professional and together in a group that might have helped them, at least our qualitative data showed this, that it helped them to be part of a group and all of them experienced this kind of silent condition. And whenever the silence happened in nature, the positive outcomes received another boost. Eric told me that in the German language, there is no plural of silence.

20:12He loves that in English you can have silent says, opening up this idea that there are different kinds of silence. Context is important, as his research shows. Are you indoors or outside? Alone or in a group? It all affects the quality of your silence. Professor Trevor Cox said that what we're looking for isn't silence, but nature. So I thought I'd try and sample some silence outside.

20:43It shouldn't be that difficult to find silence in London. I mean, it's a big city, but it does have a lot of big parks. And there's one just around the corner from the BBC. and I've come to it, Regent's Park, to see what silence feels like.

21:05Only it's not silence because I can hear the guy in the distance with some sort of leaf blower. I can hear water tinkling in the background. There's the occasional car noise.

21:24magpie it's quite a busy soundscape and yet it does feel quite tranquil here but I think that might be nothing to do with the soundscape I think even though I can hear the leaf blower I can hear the water I can hear traffic in the background there's nothing immediate in front of me apart from greenery and some beautiful trees. And maybe that's why I'm finding this a tranquil environment.

22:06So, being able to enjoy silence, or relative silence, let's say, might be about what you're seeing around you, not just about what you're hearing. Where you are seems to make a difference in how you feel about silence. Remember, our listeners Ichi felt uncomfortable when she was at home alone with silence. Is her fear of silence actually a fear of being alone? We know that humans and many, many animals, again, this is a phenomenon that is very widespread. is this notion of safety when you're surrounded by others. Marta Moita, the neuroscientist you heard earlier who made the discovery about rats and silence.

22:53There's very good reasons for this. So one is very simple. Actually, I think the simplest one is the most difficult to demonstrate. But it's basically, if you are in a group and there's an attacker, then just from the fact that there's multiple targets around you, It decreases the chances that you're the one being targeted. So on one level, this is just a numbers game. You're safer because your odds of being attacked come down. So now imagine if you're alone, you're going to be in a higher alert state because you feel like you're less safe. And then silence yourself, I think, could be a telling signal that you are alone.

23:42So probably the reason why some people like to have the TV or the radio on, you know it's still a TV that is not going to defend you, but you feel safer because you're surrounded.

24:00There's safety in numbers, as the saying goes, and that may be key to Zichi's dislike. there are some very good reasons for being afraid of silence. Talking of which, I wanted to finally experience some.

24:19Trevor, we are in an extraordinary room and I'm not sure I can do it justice with the explanation. Can you describe the walls and the ceiling to me? So basically what you can see is everywhere you look are wedges of foam. They're quite deep and they're on the ceiling, they're on the walls. Actually on the floor as well there's a net there so in case someone drops their foam it doesn't disappear. So actually every surface in this room is covered in foam absorbance. Trevor Cox, the professor of acoustic engineering you heard earlier in the show, has taken me into the University of Salford's anechoic chamber, a room without sound.

25:00The idea here is when I make a sound, you just hear me direct, but you hear no wall reflections, no ceiling or floor reflections. So from an acoustic point of view, there is no room. What's it used for? Well, it's when we want to get rid of the room. So if I was to, say, measure something like a loudspeaker, you want to see how loud that loudspeaker is making sound in lots of different directions. You rotate it round. If you do that in a normal room, you get all the room reflections. We want to measure just the source, just the loudspeaker on its own. So we bring it in here where there's going to be no room effect.

25:35Have we got time for me to just sit here in a bit of silence? Do you want me to go and turn the lights off?