In fact, this second theory is more literally true of the Belcerebon people of Kakrafoon Kappa.

7 seconds sound clip from The Hitchhiker's Guide to the Galaxy (1981) - Episode 6 sitcom.

You can hear this line at 00:07:40.469 in the Blu-ray version of the TV Series.

Quote context

[...]

- Or, 'So this is it, we 're going to die. '

- At first, Ford had formed a theory to account for this rather strange behaviour.

- 'If human beings don't keep exercising their lips, he thought, their mouths probably seize up. '

- After a while, he abandoned this theory in favour of a new one.

- 'If they don't keep exercising their lips, he thought, their brains start working.'

- In fact, this second theory is more literally true of the Belcerebon people of Kakrafoon Kappa.

- The Belcerebons used to cause great resentment and insecurity amongst neighboring races by being one of the most enlightened, accomplished, and, above all, quiet civilizations in the galaxy.

- As a punishment for this behaviour, which was held to be offensively self-righteous and provocative, a galactic tribunal inflicted on them that most cruel of all social diseases, telepathy.

- In order to prevent themselves broadcasting every slightest thought that crosses their minds to anyone within a five-mile radius, they have to talk loudly and continuously about the weather, their little aches and pains, the match this afternoon...

- And what a noisy place Kakrafoon has suddenly become.

[...]