Bruel And Kjaer 4228

The Bruel & Kjaer Pistonphone Type 4228 is a small, battery-operated, high-precision sound source and it provides quick and accurate calibration of sound measuring equipment including sound level meters. With the included barometer, it satisfies IEC 942 (1988) Class 1L while, with an external barometer, it is capable of satisfying Class 0L of IEC 942 (1988). It also satisfies ANSI S1.40-1984. It can be used in the field over a wide range of temperature, humidity and pressure while still maintaining high accuracy. It is extremely useful for supplying a standard sound pressure level. Each pistonphone is individually calibrated and comes complete with adaptors, allowing calibration of 1", 1/2", 1/4" and 1/8" microphones.

Features:
124 dB SPL at 250 Hz
Satisfies IEC 942 (1988) Class 1L or Class 0L (with external barometer) and ANSI S1.40-1984
High frequency and level stability
Individually calibrated to within 0.12 dB (including effects of specified microphones)
1", 1/2", 1/4" and 1/8" microphones