Stomp stomp
Whirrr.
"Pleased to be of service"
"Shut up"
"Thank you"
Stomp stomp stomp stomp stomp.
Whirrr.
"Thank you for making a simple door very happy."
"Hope your diodes rot."
"Thank you. Have a nice day."
Stomp stomp stomp stomp.
Whirrr.
"It is my pleasure to open for you..."
"Zark off."
"...and my satisfaction to close again with the knowledge of a job well done."
"I said zark off."
"Thank you for listening to this message."
Stomp stomp stomp stomp.
"Whop."
Zaphod stopped stomping. He had been stomping around the Heart of Gold for days, and so far no door had said "whop" to him. He was fairly certain that no door had said "whop" to him now. It was not the sort of thing doors said.
Too concise.
Furthermore, there were not enough doors. It sounded as if a hundred thousand people had said "whop", which puzzled him because he was the only person on the ship.
It was dark. Most of the shop's nonessential systems were closed down. It was drifting idly in a remote area of the Galaxy, deep in the inky blackness of space. So which particular hundred thousand people would turn up at this point and say a totally unexpected "whop"?