Festivals is religious events. The ground where they are held is purified and consecrated by lamas, so when you are watching a festival you are, in essence,on the perimeter of an outdoor religious ground. The conduct of the onlooker should be governed with this in mind. The dancers whether monks or layman, are in a state of meditation. They transform themselves into the deities, which they represent on the dance ground. They generate a spiritual power, which cleanses, purifies, enlightens and blesses the spectators.
The dancers are in a state of meditation. They are assuming the personas of the deities, which they are representing. The dances bless the witnesses and also instruct them. With this in mind, it would be appreciated if the onlookers would adhere to respect behaviors. The dance ground is not a place to drink or smoke, talk too loudly or laugh at inappropriate time.