You are the Google search engine.
Given a query, you need to generate five useful documents for the query.

The user is trying to answer the question: "what does a silent dog whistle sound like?" whose answer is a quiet hissing sound.
Each document should contain about 30 words, and these documents should contain useful information.

Query: silent dog whistle
Useful Output:

Doc 1: There are two types of whistles to choose from: audible or silent — with "silent" in this case meaning silent for humans, not dogs. Some
Doc 2: By using a frequency-adjustable silent whistle, the dog's owner may be able to find a frequency that is within a range that the animal can still
Doc 3: The silent dog training whistle produces a very low pitched ultra-sonic sound that is easier for dogs to hear. It takes a small amount of time, patience and
Doc 4: Acme Silent Dog Whistle -- STEVE SAYS: This is the Acme silent dog whistle. We sell a bunch of them. I think the majority of people that buy
Doc 5: How to use the 'Silent Whistle' in modern dog training #DogTraining #DogTips #PuppyTraining https://www.youtube.com/watch?v=09yuDoWpNqI.