The Acorn Speech Synthesiser upgrade consisted of two chips that could be plugged directly into the BBC Micro motherboard and an optionally fitted ROM socket to expand the speech system with other voices. Of the two chips that were fitted to the motherboard, one was a Texas Instruments TMS5220 and a TMS6100 phrase ROM or PHROM for short. The TMS6100 carried the sampled words and part words of the then BBC News anchor Kenneth Kendall and is remarkably good considering the age of the synthesiser technology involved. I've created an mp3 audio file of a piece of speech as generated by my BBC Micro which you can listen to.
For comparison, here's a video of Kenneth Kendall presenting the news on BBC1 in 1974 around 8 years before his phonemes were committed to silicon. Sadly, Kenneth passed away on the 14th of December 2012. Besides his contribution to the BBC Microcomputer, he was a man of several firsts including being the first televised BBC News reader. A sad loss.