The hidden speaker was positioned between two wooden rods -- one swabbed with a female's scent and the other 'unscented' -- so that the sounds and the scents came from the same location.
In general, the lemurs paid more attention to the sounds and smells in the matched trials in which the call they heard and the scent they smelled came from the same female, than in the mismatched trials when they heard one female and smelled another.