who is laughing in dark side of the moon
Peter Watts
The Dark Side of the Moon
The band's road manager Peter Watts (father of actress Naomi Watts) contributed the repeated laughter during "Brain Damage" and "Speak to Me". 
wiki:11631946
The Dark Side of the Moon [SEP] Voices
His second wife, Patricia "Puddie" Watts (now Patricia Gleason), was responsible for the line about the "geezer" who was "cruisin' for a bruisin used in the segue between "Money" and "Us and Them", and the words "I never said I was frightened of dying" heard halfway through "The Great Gig in the Sky".