Chris - What is your voice and how does it work?
Kirsty - The voice is a bit like an instrument when we produce a vowel sound where we have the mouth and throat (the vocal tract) acting as a resonator. We have air coming from the lungs making the vocal chords vibrate very rapidly and the vocal tract will emphasise some frequencies a bit like the te body of a flute or clarinet.
Chris - You have a bit of a twang that says... down under. You sound a bit different to me, why is that?
Kirsty - Different language communities have agreed different targets for what the sounds of language should be and how they are going to realise them. Comparing a british and Austrailian accent the vowels sounds are different, eg the a sound in park is differnt. I produce it with my mouth and toung a bit higher and with a bit more nasalisation.
Chris - It is all learned isn't it?
Kirsty - Yes, it is agreed by the community and you learn your accent as a child.
Chris - I can begin to do an austrailian accent... G'day mate... but Rory Bremner does this brilliantly and sounds like tony blair etc. So when I try to sound like you what am I having to do? Is it like changing you accent?
Kirsty - Within a language community, it isn't really adopting an accent it is copying more individual habits, if you are trying to change your accent you are trying to change your linguistic targets to those of eg. Austrailians.
Chris - Kat has brought in some instruments. You are going tou use these to illustrate the difference between a man and a woman's voice.
Kirsty - We are going to show the difference between the resonances in a shorter female vocal tract and a male.
Kat - I have a B flat clarinet which sounds like this...
Kat - And a bass clarinet which sounds like this ... much deeper
Kat - So it is the same timbre of sound but the bigger one is much deeper.
Chris - so it this like the difference between a male and female voice?
Kat - It is in the sense that the female vocal tract is shorter than the male one, but the different vowel sounds involve changing the shape of the resonantor using the tongue and lips rather than changing its length.
Chris - Does this mean that really good singers have exactly the right head anatomy to sound really nicest resonances?
Kat It is to do with the head anantomy and also the control that such people have developed over the years.
Chris - How would you analyze a voice?
Kirsty - This is where a witness has heard a voice at a crime scene and thinks that they could recognise it again. So a bit like an identification line up.
Chris - Can we do this by computer, as the stress of a situation could distort someone's memory?
Kirsty - This type of evidence is only used in a very limited set of conditions, the witness would have had a resonable amount of exposure to the voice in question.
Chris - How can you use a computer to help an identification?
Kat - In forensic situations when you have a recording of a voice you can use a computer to do an analysis of a recording, this is normally a different situation as you rarely have a tape recorder running when you are attacked.
Kat - What are the most identifyable parts of the voice?
Kirsty This is a big problem for us, and actually we spend more time pointing out the problems with voice identifications than making them. There is no 100% reliable technique for identifying people from a recording of their voice. We just put together a whole series of indicators.