The Science of Sound

Hello, this is the Infinite Monkey Cage and he is Brian Cox.

His favourite law is the second law of thermodynamics.

I would go so far as to say that it makes him hot, but clearly it doesn't, or at least not for very long.

And here's Robin Ins and his favourite law was Hooke's Law until he found out it only applies below the elastic limit.

Why?

Only below the elastic limit?

Yet again, Wikipedia with its information ruins my life.

Today we are looking at the physics of sound.

As we're discussing sound, we've come to the home of the BBC Philharmonic here in Salford.

Sadly, though,

we couldn't afford the whole BBC Philharmonic because I fritted the entire BBC science budget away on volcano-resistant shoes and Gore-Tex.

Only you hadn't used the helicopter to get here.

I was so looking forward to having a violinist.

So we had a whit round and we got just one.

So please welcome this week's special guest, violinist Julian Gregory.

For regular listeners who might not know we always have a regular violinist because they haven't had it, we do always have a regular violinist, but they normally get cut out from being rubbish.

Julian, this is a no-pressure situation.

Violin for us.

Jaunty, I like my science.

Jaunty.

That's enough, that's enough, don't overdo it.

In today's show, we'll be seeking scientific answers to questions such as: what is the most terrifying noise to human ears?

And what are the probable evolutionary reasons that we find these sounds disconcerting?

Sounds such as.

Yeah, it's going to be an amazing science show.

Why would we find the sound of a drill that we normally think of as going into our teeth and creating agony?

Why would we find that disconcerting?

We'll be giving you scientific reasons.

And why do certain sounds just make us miserable?

Yes, we're in Salford, so we are playing the Aren't Cockneys miserable, unlike you, lovely northerners, card.

So,

what is the science of sound?

Help us find out.

We're joined by a panel of experts and a comedian because we think comedy helps the average listener comprehend the complex nature of the natural world.

Yes, for instance, I only understood the ramifications of the relativistic nature of time when I went to see Ken Dodd.

3 a.m.

before the first interval, 3 a.m.

Joining us today is Trevor Cox, who is a professor in acoustic engineering.

His special interest is the perfect design of rooms for intelligible speech and music, which is why he's banned from Radio 1.

Professor Chris Plack holds the Ellis Leward-Jones Chair in Audiology at Manchester University, and he's published over 50 articles in peer-reviewed journals, including the effects of low- and high-frequency suppressors on psychophysical estimates of basillar membrane compression and gain, popular one.

And

I got a laugh.

Available in all good bookshops.

And

off-frequency growth of masking effects of masker duration in forward masking.

Further evidence for the influence of the peripheral non-linearity.

As if further evidence was required.

You're right there, Brian.

I think we've got enough, haven't we, on the peripheral non-linearity nowadays?

Finally, Tom Rigglesworth is a comedian and winner of So You Think Your Funny competition in Edinburgh.

He was also nominated for the Edinburgh Comedy Award and has also won a Sony.

But today he's returned to his old stomping ground, the Acoustics Department of Salford University.

That should be made clear that do not stomp in the acoustics department.

It may affect the results of some of the experiments.

And this is our panel.

Trevor, we're in this room which has been specifically designed for classical music, the home of the BBC Philharmonic.

Is the design of concert halls, would you say, a science?

Is it an art?

Is it architecture?

Is it some kind of mixture of the three?

It's probably a mixture, but I think in this room, there's more science in here than probably art, because this is

maybe I should rephrase it.

Even when the orchestra is in the design of the hall, there's probably more science than art because it's specifically designed for recording in.

So we're not trying to create a great architectural space for audiences normally.

So as you look around this room, you'll see perspex, bent shapes above us, reflectors.

They're specifically there to give reflections down to the orchestra so they can hear themselves.

We have all these strange, slatted things around the walls, which are all specifically angled to give reflections to help the orchestra hear each other.

So, there's a lot of design work gone into making this sound exactly right, and that is a science.

Now, why is it we went off on a tour a while back and found that concert halls were not good for spoken word quite often?

A couple of concert halls we played, particularly if Dara Brian talks very quickly about poorly thought-out research into neutrinos in in Hollywood movies while swearing, going, ah, there's pesky neutrinos.

If he does that very fast, it appears.

In a New York accent.

Oh, those pesky neutrinos.

Of course, because he's doing the voice from the film, you idiot.

So when we found that some people in certain corners of the concert hall, for the spoken word, it was very difficult to pick up all of the swearing.

Most concert halls, which are used for classical music, are designed first to work for the orchestra.

So they design it to have this big reverberance.

But that's not very good for speech.

That actually gets in the way of intelligibility.

It makes the words run into each other.

So, most halls, most intelligent halls, have got designs in there.

They've got stuff, fluffy stuff they bring out, literally, sort of curtains and all sorts of stuff to try and dampen the space down for when they have electronic stuff or when they have speech.

But there are halls where that isn't done very well, and yeah, it's an unintelligible mush.

See, I like there was what one concert hall we played.

The seats had been specially made to absorb sound,

forgetting, of course, that hopefully there will be people sitting in the seats, not sitting on the sound absorber.

Oh, that's that's quite deliberate because because an orchestra will rehearse in an empty concert hall and they don't want the concert hall to be very different when they come and play the concert.

I mean, if you go and rehearse in a space with wooden chairs, like a church, it will sound completely different when the congregation come in and fill up all the pews.

So, they try and make the acoustic roughly the same, empty, occupied, half full, whatever it is, it's got to be roughly the same.

So, if you had an audience that looked like most of the people were quite bony,

should you then try and compensate by asking for some people who'd let themselves go a bit to come as well to try and absorb the sound.

There was a very good paper from Australia years ago which looked at the effects of clothing on absorption.

So they had the audience in various levels of undress down to swimming trunks to see what effect it had on the absorption.

And we're going to repeat that experiment this evening.

Tom, you did a degree in acoustics here at Salford.

So what does that entail?

I mean,

is it mathematics?

Is it a mixture of physics?

Is it a mixture of engineering?

Well, I'm going back back

12 or 13 years.

Yeah, there's been a lot of time and alcohol between

then and now.

And I must state as well that I did study under Professor Trevor Cox here, so anything I say which is wrong,

it's not strictly my fault.

But it's basically incredibly hard mathematics.

That's my memory of acoustics.

It's really, really hard maths.

And it's good because I think that's why music is appealing really to me.

Because artistically, of course, it's very creative, but it's sort of underpinned by this very solid groundwork of physics and hard maths.

And that's what I'm really fascinated by that, the sort of the joining of the two, which is why these rooms are really interesting.

Because I know it looks awful, but it sounds so alive.

And you can create great art in here, but it's all underpinned by this real bedrock of hard maths.

So, do you think that means people enjoy, you know, as a mathematician, you go, well, of course, I enjoy enjoy Beethoven a lot more because I understand it mathematically.

Whereas those people who can't do the sums,

you get musical snobby, though, don't you?

You get jazz, and jazz is even harder, like harmonically and mathematically, to unpick than X Factor, for example.

So, yes, I think musical snobs would argue that they understand it more, therefore enjoy it more.

The same way that people might like fine wine as opposed to Vimto.

I mean, Tom, we're going to come back actually to the mathematical underpinnings of music.

Let me ask Chris first.

We're talking about sound in this room, and I suppose to a physicist, sound is very simple to define.

It's just a pressure wave going through air.

But is there more to it, or is that it?

Would that be how would you define it?

Well,

I think there are two definitions, really.

You can either define it in a physical way, which is just pressure variations, doesn't need to be air, it can be any medium at all, or you can define it as sound is something that we hear.

And that goes to the essential question: you know, if a tree falls in the forest, for no one there to hear it.

That's philosophy.

Well, no, no, no.

It's a new definition.

If a tree falls in the forest, no one there to hear it, then according to the physical definition, yeah, there's a sound because you're still getting pressure variations.

But in terms of the psychological definition, then no, there wouldn't be a sound because there's no one there to hear it.

You've got to have a receiver to validate

the definition.

But I mean, the interesting thing is when you have sounds which aren't actually in the physical world, but you hear them.

And one example of that is, I don't know if anybody here has tinnitus, where you have sort of ringing in your ear.

If you listen to, and lots of people are nodding out there, I get it a bit.

If you've listened to a lot of loud music in your life,

you can often damage the ear a little bit, and that can create these sort of phantom sounds.

And there's no sort of physical pressure variations going on, but people still say they hear a sound.

I mean, I do find it very weird when you say the thing about when a tree falls, the sound does occur.

Just because we didn't experience doesn't, to me, there aren't two separate arguments.

But I was talking to you beforehand, come on here, where when I'm on a plane at high altitudes, I seem to be able to hear music very specifically as if it's actually in my ears.

And it's and this may well be a cry for help.

And I wonder if there is something which is changing my perceptions.

It's not with my ears popping or anything like that.

I can actually be sitting there with no headphones in or anything like that, and I can hear very clear music.

And it's kind of not just things, ideas that I'm picking out from the air around me, it's specific songs.

Now, is there a way that a brain changes the way it perceives sound or the way that it can itself create the imagination of sounds?

Yeah, I mean the brain is always trying to form order out of disorder.

So if you give it you know you're in a plane there's a lot of noise when you think about it, you know, I don't know what the sound level in a plane is, Trevor probably knows.

So 80 dB, 90 dB maybe.

So it's pretty high sound level.

And but it's basically just noise, it's just a formless shh kind of sound.

And because your brain's always trying to impose just like even at clouds, you see sort of faces in clouds and animals and things like that.

So perhaps your brain is doing a sort of good job of trying to extract some meaning from this sort of meaningless noise.

I mean, to me, that's an interesting thing.

When we are listening to music, when we listen to noises, how much do we as human beings still place our own personality, our own perception?

Maybe, maybe, Travis, you know, but how much in terms of our own perception changes what we might be hearing compared to what other people are hearing?

Well, there's the things which are culturally learnt, such as the scales that we listen to.

So if I go into Asia, their musical scales are quite different from the musical scales we get in Western countries.

And if I listen to Asian music and I'm not used to it, I think it sounds a bit odd.

But obviously, that's what Asian people listen to.

So, we can learn what we want to listen to.

You can decide to associate anything you like.

So, we tend to associate minor scales, minor keys, with sadness, but you could associate it with nice, jolly things if you wanted.

Can you really?

Julian, perhaps you could

give us a minor scale.

A minor scale sounds like this.

Now, that does

indeed, as everybody knows, sound sad.

That's a sad song in a minor scale or a minor key.

Is that learnt?

Have we learned that that progression, that harmonic progression, is sad, or is there something inherently sad about it?

I mean, lots of scientists have looked at this, but the present sort of kind of understanding is it's a learnt response.

You might be hearing to these sounds, even from in the womb, you can hear some music going on, and you start to associate these sounds with different events, and people will learn that that means sad.

So, well, so could you test it then there?

If you kidnapped two identical twins

and played one constantly major scales, happy, happy music book, but showed them images of train wrecks and haunted houses and graveyards and Sheffield United winning the cup and you know terrible events, and then had the twin with

a minor scale, of course, showing him Wednesday winning the cup, showing lovers reuniting at train stations, candy floss, happiness.

Would that completely reverse?

Or would you just get charged for kidnap?

I tried to get ethical approval for such an experiment, but unfortunately, the ethics committee wouldn't allow me to do it, so we'll never know.

I mean, the experiment's kind of been done, right?

Because in the Middle East,

minor scales sound associated with happy music, right?

Can you do it?

So that suggests that there's a tempo element to it.

Well, actually, Trevor, you might start by outlining what a scale is.

So, physically, what is it?

Well, we can't play every single frequency that's available to us.

Because actually, I mean, on violin, obviously, you can play Glissando and just have every frequency playing.

But if everyone was playing any old frequency like as a group, it would just sound awful.

It would sound terribly distant and really horrible.

So, we have to know there's certain frequencies we have to hit, so the notes will go nicely together.

So, we know that if we have an orchestra playing and they're all trying to hit those frequencies, we've got a better chance of it sounding nice together as if everyone's playing any old frequency they want, where it just sounds terrible.

And why those particular notes?

What is it that we talked earlier about or mentioned that the mathematics of music?

So, what is it mathematically that defines the notes that we happen to have chosen in the West?

Well, it it goes back actually to Greek working out how notes are interrelated.

So, notes which go nicely together, together, I say a note and a fifth above.

Would you like to just play that for us, Julian?

Those notes just sound naturally good together, and actually, they're closely related mathematically.

One's one and a half times the other frequency.

So, that we know when you play a note on an instrument, you don't just get the frequency of that note, you get all these harmonics, which are more multiples of those frequencies, and they come out as well.

And how those different harmonics interact determine whether the notes sound nice together or sound nasty.

And so, our scales are largely constructed in Western music about how the different notes sound in pairs or in large groups in chords.

Tom, what always fascinates me is how I think it was Pythagoras that invented the idea that the fifth, as Julian played before,

and the fourth

are so closely linked that anyone that's learned a musical instrument will be aware of the one, four, five chord progress.

Exactly.

So

Pythagoras unwittingly wrote the entire status quo.

And that is why, that is why, I mean, I think Pythagoras did some excellent work with I love his A squared, B squared, C squared stuff, but it is why I won't have triangles in the house.

I think

But he was in he was a founder member of status quo, wasn't he?

Though is motorhead more Aristotelian, don't you think?

Now, Tre Trevor, I know m moving away from music, just talking about sounds in particular.

I know you ran a research project at Salford, which is a mass online experiment to find the the world's worst sound.

I think it was over a million people participated.

And I'd like to read out the top ten list first of all.

So the number one worst sound was vomiting, followed by microphone feedback, wailing babies, trains scraping on tracks, a squeaky seesaw, a poorly played violin,

A whoopee cushion, an argument in a soap opera, mainshum, and the Tasmanian devil.

Now, a Tasmanian devil,

perhaps there's some geographical response of the people.

But so let's take a few of those.

Maybe vomiting.

Why would that be the number one

most objectionable sound?

I'm just amazed you didn't go from ten down to one.

You had the chance to have the top of the pops music on and relive your youth then, and you missed out.

Well, we were, do you know, at one point we were going to have the sound effects for all these things, but thinking that possibly playing the top ten most hated sounds may well be a big turn-off.

Yeah,

I'm turning over to radio too.

But again, there must be some, I mean, from an evolutionary perspective, we must have some insight as to why sounds like that.

Let's take vomiting, for example.

What is it?

I mean, I know what it is, but

that's what I like about your science.

We have to start with the basics.

I mean, there's a well-researched phenomenon called the disgust reaction, which is meant to help us catch disease.

So we try and stay away from things that might have disease in them, like vomit, for example.

So we have a repellent reaction to bodily fluids and nasty stuff, and that's meant to protect us from disease.

So it would seem logical that the sound of someone being sick is going to be repellent because it's a sign of someone ill, maybe, who's carrying a disease that you need to get away from.

But I'm interested just in the audience, because I don't, Tom, I mean, what would you put as your, you know, out of that list there, vomiting, microphone, feedback, wailing babies, train train scraping on tracks?

Is there one there that you think?

Train scraping is awful.

Microphone feedback, I can't stand.

I mean, a lot of those overlap, really, don't they?

They're very high-pitched, scratchy sound.

So, so, what is it about high-frequency sounds?

They seem relatively unnatural in this case.

I mean, most of them are modern, microphone home, trains, etc.

I don't think we really entirely know why they're very unpleasant, but one of the suggestions which goes back to the early 80s work on this is that actually these sounds are a bit like the sound of someone screaming.

So, you take fingernails down the blackboard, it's got a certain kind of frequency and a certain roughness to it that you also get if you let rip with a very big scream.

So, maybe there's a connection between the sound and distress cries, and that might be what we're reacting to on a very simple level.

But I don't think anyone's actually really done any experiments to show this is true or not.

See, I think that I don't know what other people think, but I disagree with the, you know, I'm sure I'll ask you to disagree with that question.

No, I do disagree with it.

No, no, no, no, no, I don't know.

It certainly doesn't have to be for support.

But I

did that every time I keep looking at this list,

and vomiting.

I understand vomiting, right?

Fair enough, but squeaky seesaw, right?

Vomiting, oh no, someone's sick and they're full of disease.

Squeaky seesaw, oh no, happy children.

It's really to me, I mean,

there's some of these which are whoopee cushion.

I don't see, in fact, Trevor, am I right in saying you were once in the Guinness Book of Records for did you possess the largest whoopee cushion?

I did at one point have the world record for the world's largest whoopee cushion indeed.

And was this part of the research?

No, I think the big whoopie cushion came after this one.

That was a a stage prop for a stage show because actually a whoopee cushion, the output of it, behaves very much like, say, when you're blowing a trumpet or when you're at the read of a saxophone or something like that.

So it was used as a prop to explain how musical instruments work.

But it actually, unfortunately, I lost the record to a friend who broke it, and the record currently is, I think, three meters in diameter.

Is that all?

And it was here that Tom saw his dream begin.

I could train every day for five years.

I'm not going to beat you saying bolt, but I could make a whoopee cushion 3.1 meters in diameter.

The physics, unfortunately, defeats you because what happens is you get bigger and bigger, it goes lower and lower in frequency, so it gets less and less impressive, and it's still got to make the sound.

So there is a physic limit to how big the world's largest whoopie cushion could ever get.

Dang!

Isn't it awful when a rude parp is defeated by the laws of physics?

Yeah,

one of the other areas, just going to kind of a broader pop culture area as well, is the way that sound is used.

Sound design in popular culture, for instance, in films, where very rarely now, you know, the amount of orchestration you hear in the average film is where we are constantly being manipulated to have emotions beyond just what we're seeing visually, beyond the voices, what we're hearing.

That we're constantly, I watched Crime Watch the other day, and there was a sad scene where something sad happened, and you knew it was sad because someone had died, but they still went, We better put some sad music on as well, because then they really know it's meant to be sad, not one of those funny someone's died moments.

But this is, you know, sorry, Tom, yes, can I tell you a story about when I was nine years of age?

It depends.

On my ninth birthday, right, this is completely true.

My granddad died, right, which was both disappointing as it was selfish.

I thought you were going to.

Yeah, yeah, yeah, you can.

Shall I say that again over the top of the?

Okay.

If you can just fake a comical reaction

when I was nine years of age, my grandfather passed away on my ninth birthday, which was as disappointing as it was selfish.

Anyway, we went to the funeral, right?

And I'm from a very emotionally repressed family.

I mean, it's just Yorkshire, so we're all a bit backward emotionally.

But we went to the church, and I was only nine years, I was nine years of age.

And in the funeral,

I wasn't used to seeing the output of emotion from all the grieving relatives.

It completely did me in.

It completely flawed me emotionally.

I was on the ropes.

I was seeing everybody sobbing and weeping and hugging, and I'd never seen anything like it.

So I was just in pieces, pieces, right?

And then one note happened in the hymn.

That note made me cry so hard, it almost turned me inside out.

I can't describe the rush of emotions just went whoa like that out of me.

I had to be sent home from a funeral.

I've probably been the first person ever to be thrown out of a funeral.

I was sent home for a funeral.

And then a few years later, we inherited the piano.

My granddad didn't need it anymore because he was dead.

So, messing about on the piano, I picked out this note, and it's called the devil's note or something.

Can you do it, Julian?

Just that one bit for that?

That distance there is a tritone, it's three notes apart.

And it does have a very special effect, it's really useful in music for giving an effect.

I mean, it's interesting that we're talking about how different cultures perceive music and the way it works.

I think that for everyone has got to be spooky.

So, I don't know if it's anything which is indigenous in the culture.

I believe, as a musician, there are effects that you can make that you can give to people just simply by what you play, and that will work for anybody.

And I can frighten anybody with that.

So, we were just talking about in films, for instance, where something we're chatting about before, where you have, when you, you know, Hitchcock knew with with bernard herman you know the incredible moments there where why can we just play i suppose the most obvious one is is to go for for psycho there where

so that is i presume it's that again that's the nails on the blackboard that's that kind of that it's putting us really on edge if as if seeing someone in drag stabbing a young woman to death isn't enough

I think there is that sort of fingernails down the blackboard quality, but there's also the fact that it's repetitive and you don't know when it's going to stop.

And that's something which can add to horribleness.

Is if you do it over and over again, and you can't escape it.

So, we know if you haven't got control of a sound, your reaction to it's much stronger.

And then, something like the Jules one, which again is probably one of the most famous ones.

I don't know if you can.

Can you do that on the Violings?

I know it's more.

I've been looking at Jules, and it's really clever because he uses several different techniques to get you to feel threatened.

One of them is to start with one note.

This should be on the cellos and basses who are over there,

or at least

they normally are when there's a full budget.

Couldn't afford them anyway.

This is the pattern,

which you all know.

Immediately, that sounds threatening.

He adds another one.

So you know something's approaching.

Actually, this is not going away.

Something more is going to be.

And then the next one is four notes.

And then it speeds up.

So it's obviously getting not only closer but more aggressive.

So now you really get a sense of something approaching.

That's psychological.

What I like though is that with the violin rather than the cello there, it does make for a jauntier shark.

It does.

It's a shark that's going to come out and then go, damn at a kid.

We'll very quickly just go through the audience questions.

We asked our audience, if you could take one sound to a desert island of silence, what would it be and why?

We have taken out the 500 answers that were Brian Cox's voice saying everything's nice.

But yes, we did note them, don't worry.

Here's one from Ian Fitter: John Infinite Monkey Cage's track, four minutes and 33 seconds of silence, which four minutes and 33 seconds is basically four minutes and 33 seconds of silence, just for the irony.

I like anyone who's going to go to a desert island and go, I think irony will still be effective here.

We've got here the sound of rain to remind me of Manchester.

The voice of Brian Blessed saying, Dive!

In

that's in Flash Gordon, because I need cheering up.

That's Richard Frost.

Can you imagine that on a desert island?

Every foreigner, dive!

Oh, Brian!

The clucking of a gilded chicken.

Now you wait for this one.

Because silence is goldhen.

Pete Jackson, you know who you are.

That brings us pretty much the end.

Thank you for those answers.

There we are.

Next week, it is the ultimate showdown.

It is chemistry versus physics.

Not really any point to that show.

But nonetheless, we've invited a couple of test chief twiddlers and magnesium strips trumpets onto the show for amusement purposes, you understand.

Yeah, so thank you to our guests Tom Rigglesworth, Trevor Cox, and Chris Plack.

And we thought we'd end the show with a song.

We've been talking about the fact that songs in many ways almost feel adhesive to the brain and that you just really get stuck in your brain.

So, Brian has gone over to the Steinway that was flown up here

from one of his houses.

And

I have to say, this wasn't my choice, this song.

I'd like to apologise for the fact you're all going to go home with it, and it probably won't leave you for days.

Here's Brian and Julian with what I think is going to be a number 27 Christmas hit,

ABBA.

Thank you, and good night.

That's a nice page.