Reliable metrology for infrasound sensors

The reliable assessment of infrasound has become increasingly important in the last years. Reliable measurements require calibration of the employed sensors with traceability to the SI. While there is measurement equipment capable of measuring infrasound available, there is no sufficient calibration below 10 Hz. Traceability for airborne sound is currently realized by primary calibration methods which are applicable down to 2 Hz, with limitations below 10 Hz. Against that background, a primary and a secondary calibration setup have been developed at PTB. Together they enable the traceable calibration of a variety of infrasound sensors such as microphones, sound level meters or microbarometers. Moreover in practice, procedures are necessary which ensure reliable results in a field environment even with external disturbances. A field study was conducted comparing the performance of measurement microphones and microbarometers at a wind park. Emphasis was placed on different means of protection against wind induced noise. Additionally, a laboratory study investigated the influence of small damages to a microphone diaphragm on the reliability of the microphone. In this contribution, the newly developed calibration setups for infrasound sensors and the insights from the field and laboratory studies are presented.