MMario: And can you really claim a pattern of speech has changed if the result is not audible?

Yes, sure, you can and any other argument has not been taken serious in science since about the middle of the 19th century. A change doesn't have to be perceptible (I'm using the superordinate word for both 'audible' and 'visible' to show that apples and oranges have a clear and easy to spot tertium comparationis in this case) in order to be real.

I'm truly sorry, MMario, if I have erroneously mistaken this sentence for cheap science bashing. If you had written something like is it worth studying such tiny differences I wouldn't have reacted with that somewhat harsh one-liner.

The idea behind studying tiny differences in speech patterns is to make automatic voice recognition more reliable. You want to find out which changes belong to the same person (on a different day) and which changes indicate a different speaker. The disabled persons using automatic voice recognition to help them through their daily lifes are extremely thankful that the apparatus most times still recognises their voices even after a bad sleep or with a sore throat.

The Queen is nothing but a perfect subject for such studies for her speeches are preserved and all of them are delivered in a very standard low emotion voice.

Wolfgang