The science of Christmas carolling

Christmas carolling is one of the traditions that really has stood the test of time. But why? It could be that singing and in particular choral singing, has some effects that other group activities don't... Jude Brereton teaches the science of singing at the University of York and began by telling Chris Smith how we sing.

Jude -  We can think about the voice in three main parts.  You need a power source, a sound source and then some sort of modifier, some resonator.  The power source for singers is the lungs and it's air from the lungs.  So, we need to think about our breathing.  We need to concentrate on breathing, breathing deeply, breathing regularly, and controlling that breath.  That's the fundamental to good singing.  The sound source is in the voice box or the larynx in the neck.  It's actually a pair of tiny vocal folds.  Some people call them the vocal chords.  They're about the size of your thumbnail and those vocal folds, they vibrate as you push air up through the trachea, the vocal folds vibrate and that's the fundamental...

Chris -  There's one on each side, isn't it?

Jude -  One on each side, absolutely.

Chris -  They meet in the middle and they can move apart and move together.

Jude -  They do and they do that very, very rapidly.  So, if one of our singers were to sing let's say, a middle C on the piano, that's around 260 hertz, that's 260 vibrations per second.

Chris -  So that would mean my vocal chords are opening and closing 260 times a second.

Jude -  Absolutely.

Chris -  And that is interrupting the flow of air coming out of my trachea, the windpipe.

Jude -  Absolutely.

Chris -  260 times a second.

Jude -  Yes.

Chris -  So, what does that then do to the sound as it comes up my throat then?

Jude -  That makes actually just a very simple buzzing sound.  So, I've got here an electrolarynx.  This is a device you would need to use if you had to have your larynx removed and it just makes a buzzing sound.

Chris -  Sounds rather rude.

Jude -  It does.

Chris -  It's literally the size of a stick of dynamite.

Jude -  It is.

Chris -  It's a little cylinder.

Jude -  It is and that buzzing sound, that rude buzzing sound, that's the sound we would hear if we were to get our singers and chop their heads off.  That's the sound we would hear just directly above the vocal folds.

Chris -  You've got the Templar Scholars here and they're wearing a fashion accessory I haven't seen for about 20 years.  They're all wired up.  I've never seen a choir wearing electrical apparatus resembling chokers.

Jude -  Yeah, I'm amazed.

Chris -  What is this?

Jude -  They've allowed me to put electrodes on their necks.

Chris -  That's so we can strangle them if they don't sing well.

Jude -  Yeah, we could probably do that.  So, the electrodes we got there, there is a current going from electrode to the other.  So, they've got a pair of electrodes - one on each side of the larynx.

Chris -  There's a little belt like a choker thing and it's got these two disks.  They're about 2 pence piece size sticking on the side of their neck.

Jude -  Absolutely and it's attached with Velcro at the back, so you can take them off if you begin to feel too uncomfortable.  But what it does allow us to do is to find out more about the actual vocal fold vibration itself.  So Chris, if we ask the choir to just sing one verse of a Christmas carol, we'll have a little listen later to just their vocal folds.

(choir singing...)

Chris -  Very much enjoyed the singing.  What did we capture electrically from their larynx?

Jude -  So electrically, we've just captured the raw signal of the vocal folds moving.  We should be able to listen to that now.

(electrolarynx sound...)

Chris -  Much better.  What's actually going on there?  What are we hearing?

Jude -  So, we're literally just hearing how the vocal folds vibrate.  So, that's the sound source that you put into the vocal tract and then you need the vocal tract to transform that sound into words and into different shapes of notes.

Chris -  That sound obviously isn't the sound that comes out of my mouth.  So, how do those puffs of air change as they come up and turn into A. a note and B. in my case now, speech?

Jude -  The note itself is regulated by the vibration of the vocal folds.  So we can tension and de-tension a vocal fold.  So, if they're under more tension, if they're thinner and longer then they'll make a higher note.

Chris -  Is that because they vibrate, they move up together in the part more quickly?

Jude -  Absolutely.  So, thinking about that middle C again, that was about 260 times per second.  If you were to sing an octave above that then that would be 520 times per second, and then another octave above you going 1,040 times per second.

Chris -  Are you aware of your vocal chords bouncing backwards and forwards up to 500 times a second, Victoria?

Victoria -  It's amazing isn't it when you think about it.

Chris -  Tell us a bit about your singing experience and does this sort of just happen naturally to you or have you actually had to have training and actually being aware of what's going on in your neck as you're producing lots of beautiful sounds?

Victoria -  Well, if you imagine going into a primary school playground and seeing little kids running around, the sound that they are producing is enormously loud, enormously free sound which would challenge any operatic tenor in the best London circuits.  But somehow, over our lives, as we get more stressed and more worried, all of these things shutdown.  We try and make ourselves sound better and so sometimes, singing is just a case of getting back to what's natural.

Chris -  And relaxing a bit.  So, how do I make sounds into speech then?

Jude -  The third part of the voice I was talking about, after the sound source, which is at the vocal folds is a resonator, a modifier.  That's everything above the vocal folds - the throat, the back of mouth, the tongue, the lips, the teeth, and that modifies the sound into, for example, different vowels.  So, I have here Chris, it's a very strange looking object but it's actually three...

Chris -  It looks like something out of alien actually.

Jude -  It does a little, doesn't it?  It's actually a 3D printed vocal tract of a particular singer, singing a particular vowel.

Chris -  So in other words, you've taken a scan of the innards of somebody and extracted the bit that corresponds the windpipe, vocal folds - in other words, vocal chords, the back of the throat and out to the mouth because it does end in the mouth.

Jude -  Yup and we've even got lips on this model here.  So, absolutely right.  We did that, we had a singer in the MRI scanner and they sang a particular vowel.  Now, this vowel I brought for you today is an "aahh" vowel.  What I can do is I can attach this to the buzz of the electrolarynx we heard earlier.

Chris -  So, you're just going to put some vibrations into it.

Jude -  Absolutely.

Chris -  And we're then going to see...

Jude -  And this tube is going to resonate certain bits of the spectrum and dampen other bits and it should turn it into an "aahh" vowel.  So, here's the buzz again... just a normal buzz and here's the "aahh" vowel...

Chris -  If we could change the shape of that, and we do it with our tongue presumably...

Jude -  So, by moving our mouths around, moving our tongue and moving our lips around, we can make different vowel sounds.  We can obviously make different consonants as well.  So, I can demonstrate the different vowel sounds we can make.  Here's a very strange looking object but it's actually a duck call...  And again, that's just a buzzing noise and then attached to it is a bit of hose pipe and I should be able to make an "eeh" and then an "ahh"...

Chris -  So squeezing the tube and changing the shape.

Jude -  Squeezing the tube and changing the shape.  So, if I squeeze the end of tube, I should get an "eeh" vowel because that's what your mouth is doing when you make an "eeh" vowel.  It's squeezing the end of the tube.

Chris -  Yes because you bring your teeth together, tongue towards your teeth - "eeh"...

Jude -  Absolutely, towards the mouth.  And if I squeeze the back of the tube then we should get an "ahh" vowel because that's what your mouth does when you do an "ahh" vowel.  So, I've been practicing this.  I hope it works.

Chris -  I'm glad I've got a tongue, which makes life a lot easier than actually doing that.  So, if Tori has a high voice and sings in a much higher set of notes than I do and presumably you do, is that just because I'm a different shape in terms of my larynx in my mouth to her and you?

Jude -  So, female vocal folds are generally shorter than male vocal folds.  So, they make a higher sounding pitch.

Chris -  And Tori, the other benefits of singing of course, it isn't just about making the audience enjoy it, it's enjoyable for the people who do it as well.

Tori -  Absolutely.  When you're singing, as you said earlier, an awful lot of learning how to sing is getting in touch with your breath system and that might sound similar to some of you who've maybe had hypnotherapy or other stress and relaxation techniques in the past.  You are encouraged to get in touch with your breath.  So in fact, what singers are doing is finding a way to ground themselves, calm themselves down.  Singing can be enormously beneficial for you from a very physical point of view.