This report is a documentation of the calibration procedure, and the present state of calibration of the low frequency sound level meter “Lavfrekvens lydmåler” (LFLM). The LFLM system is a sound level meter developed to measure calibrated LpA,LF values at remote positions (houses) by the occupants. The LFLM is calibrated in a special developed LF calibrator. Then it is sent to the remote user. Sound recordings are made and the LFLM is then connected to wired Ethernet and the recordings are automatically uploaded to an AAU server. The recordings are then analyzed with Matlab programs to deliver a results sheet of the measurement. The calculations of LpA,LF are based on 1/3 octave band analysis of the recorded sound. The calculations of LpA,LF are documented. The 1/3 octave filter bank is measured, and shown to be within the strict IEC 1260:1995 Class 0 limits, and the A-weighting function is concluded to comply with DS/EN 61672-1:2014 class 1. The calibration of LFLM is done at the 1/3 octave center frequencies between 10 and 160 Hz, and it is shown to be within +0.34 ; -0.32 dB of the nominal 94 dB value. This is based on an adjustment of the LF calibrator from June 2014 so any drift of the LF calibrator since then is included in the result.
|Number of pages||110|
|Publication status||Published - 16 Feb 2016|