Fox 40 Classic Safety Whistle 9902-1400 The Fox 40 Official Classic is the world's number one professional referee whistle . It's used by 90% of referees worldwide. It's also a great tool for all coaches and is also very useful for teachers. It's perfect for referees and coaches of all levels. It's reliable in any situation where it needs to be heard above ambient noise, roaring engines, and wind. Properties: Sound pressure level: 115 dB. Two chambers facing each other. No moving parts. Whistle color: neon green