N. V. Tatsenko introduction to theoretical phonetics of english

Age. Everybody knows that younger people speak differently from older people. This seems to be true in every society, and many people believe that younger people do this
specially to annoy their parents and other people of the older generation, or to make it difficult for their parents to understand what they are saying to their friends. We can look at how younger people speak and guess at how the pronunciation of the language will develop in the future, but such predictions are of limited value: elderly professors can safely try to predict how pronunciation will change over the coming decades because they are not likely to be around to find themselves proved wrong.
The speech of young people tends to show more elisions than that of older people. This seems to be true in all cultures, and is usually described by older speakers as "sloppy" or "careless". A sentence like the following: 'What’s the point of going to school if there’s no social life?' might be pronounced in a careful way as (in phonemic transcription) [wots 9э point ov gooip to sku:l if 9oz noo soujl laif], but a young speaker talking to a friend might (in the area of England) say it in a way that might be transcribed phonetically as s poi? gseo? skou f s naeo sseoJ bif.
There is an aspect of intonation that has often been quoted in relation to age differences: this is the use of rising intonation in making statements, a style of speaking that is sometimes called "upspeak" or "uptalk". Here is a little invented example:
I was in Marks and Spencer's. In the food section. They had this chocolate cake. I just had to buy some.
A typical adult pronunciation would be likely to use a sequence of falling tones, like this:
I was in 'Marks and \Spencers | In the \food section | They had this \chocolate cake 11 just 'had to \buv some