Low Noise (High Sensitivity) Measurements

Class 1 sound levels meters typically have a noise floor of 15 – 17 dB(A) so levels below around 25 dB(A) are affected by self-noise of the instrument. ANV Measurement Systems offer two ways of measuring low level noise. 

The Rion UC-35P is a 1” free-field microphone with a frequency range of 10 – 12,500 Hz. It is supplied with a 4 mA ICP pre-amplifier. It can be used with a (4 mA) Rion DA-21 data recorder under which circumstances the noise floor of the system is typically 2 dB(A). Reviewing the data from a Rion UC-35P and DA-21 requires post-processing, but this is the lowest noise/highest sensitivity system we can offer. It is suitable for measuring the noise levels in audiology booths or for accurately measuring low levels of groundborne noise for example.

The noise floor of the Norsonic Nor140 can be reduced to around 7.5 dB(A) by connecting a GRAS 40HL-N low noise microphone set whilst maintaining the full functionality of the sound level meter. The noise floor can potentially be reduced further by using Option 18 which compensates for the self noise of the instrument/microphone combination (a noise floor test must be conduected first in an exceptionally low noise situation). However this can’t be used with the instrument for octave/third octave band measurements. 

If you are not sure of the best equipment for your vibration survey call us. Our experts in sound and vibration are available during normal UK office hours.

ANV Measurement Systems UKAS Laboratory (0653), with its standard 5 day turnround, calibrates all major manufacturers’ sound and vibration instrumentation.