Bruel and Kjaer
Pistonphone 4228 provides accurate and quick calibration for various sound measuring equipment, such as sound level meters. In addition to this, the manufacturer has included a barometer, which is compatible with the IEC 942 standards of Class 1L, as well as an external barometer, satisfying the Class 0L IEC 942.
Note that the ANSI S1.40-1984 standard is met by this item, which can be used in the field at various temperature, pressure and humidity conditions, without any compromise in terms of accuracy. The item is also extremely useful when it comes to supplying a standard sound pressure level.
Some other features are the 124dB SPL at a frequency of 250Hz, along with high-level stability. Note that the device is battery-operated and can be individually calibrated to within ±0.12dB.