North West England,
The word 'sound' has two uses and meanings in English slang. The first is as an adjective, to describe a person as cool and/or easy to get on with. The second is as an affirmation, like 'alright' or 'yes, of course'.
"Have you met Josh?" "Yeah, he's well sound."
"Is it okay if we get there at about 8pm?" "Yeah, sound, no worries."