How does a whistle work? In order for the typical whistle to work you need air streams. In order to get the high pitched noise that you hear coming out of a whistle you need the air steams to interact or cross paths. This is done through the round part of the whistle, as you blow into the whistle the air travels through the loop and up again (as seen in pic below) this allows the air to cross paths with the new air coming in. At this point where the air stream crosses itself again becomes a high pressure point and the air that escapes is what makes the noise. Whistle pitch and frequency depends on the length of the whistle, the longer it is the lower the sound will be. There are other types of whistles that work in a similar concept but vary slightly. The image below is the standard whistle that I am talking about.