The Bruel & Kjaer Pistonphone Type 4220 is a high-quality sound level meter made by the renowned brand Brüel & Kjær in Denmark. This model is designed for precise measurements and inspections in various industrial and business settings.  Users can trust that the readings are accurate and reliable for professional use. The Pistonphone Type 4220 is a dependable tool for testing and verifying sound levels in a wide range of applications