It can mean extended range (hearing is often higher and/or lower frequencies), or it can just mean that sense is more 'available' for use. On a normal human, scent is much less commonly available for a Perception test than for a werewolf.
QUOTE (Running Wild)
ENHANCED SENSES
Many enhanced senses provide additional senses that the creature did not have before. These senses are treated as natural, unaugmented senses when determining modifiers for Perception Tests. When a critter has enhanced senses for a sense that it would normally possess, such as Enhanced Hearing for a hell hound, it receives a +2 dice pool modifier to Perception Tests. An enhanced sense may also provide the critter with new uses for skills. Enhanced Scent, for example, allows a trained critter to track a person or prey by scent alone.