This sound effect can be found on Cartoon Trax Volume 1, which was made by The Hollywood Edge.
Sound Effect Description
Human Whistle - ( Beckoning - 2 Types, Wolf Whistle ).
Clean, Full Length and Unedited Link to the Sound Effect
- Sonic Adventure 2 (Only used for when Knuckles' whistles.)
- Sonic Adventure 2: Battle (Only used for when Knuckles' whistles.)