NorReview: BS 4142 Tonal & ISO 1996-2 Impact Measurements

The Nor1026 NorReview Software is for post processing and reporting of your Nor139, Nor140, Nor145 and Nor150 measurements.

This articles covers tonal assessments according to BS 4142

Requirements

NorReview software must be installed, with version 6 and later with the BS 4142 and ISO 1996-2 standards and software calculation modules.

Nor140 or Nor145 instrument with at least 25 millisecond logging or better, along with 1/3 octave logging enabled and audio recording. See our tutorials on the right for meter setting configuration.

The BS 4142 & ISO 1996-2 is a paid for option and is not standard in the software.

BS 4142 2014 – Methods for rating and assessing industrial and commercial sound

Revisions in the 2014 version place far bigger penalties on the sound source under investigation for tonal, impulsive and other noise characteristics. The penalties are cumulative and can be added together to give a total penalty of 18dB compared to 5dB in the previous standard.

To assist in applying the penalties Norsonic have introduced a package of options for their meters and PC software, to give the data and answers you need.

Tonal penalty

BS 4142 2014 Annex D specifies the standard ISO 1996-2 as the method for calculating tonality in a noise source based on FFT. The standard contains an algorithm to identify tones and rate them for tonality accordingly.

To perform the calculation you should record high quality audio of the noise source under investigation. This is achieved by pressing the record button on your Norsonic 140 or 150 analyser or using a level trigger for unattended measurements.

Open this measurement file in Nor-Review. To run the tonal calculation go to calculations/ ISO 1996-2 from the menu bar. You should then click on the audio recording on the Lt graph that you want to run the calculation on. It is recommended to listen to your audio recording to be sure it is the source you are investigating. You can add markers when you have listened to the recordings to identify the relevant parts of your recording.

You can then select a highlighted area, the whole audio recording or the area you have labelled with a marker for the calculation.

Nor-Review will then run the ISO 1996-2 calculation and produce an Excel report. The Excel report will have a FFT display and a table where it lists the detected tones. The tones are reported with their Frequency Hz and Kt correction between 0 and 6dB.

Impulsive Sounds

BS 4142 2014 gives a calculation procedure in Annex E which specifies how impulsive sources should be measured and the impulsive character rated.

The measurement requires that you log the sound pressure level every 10 to 25ms. You should ensure that your Norsonic 140 or 150 is set to store the sound pressure level SPL every 25ms.

This measurement file should be opened in Nor-Review. The go to Calculations/British Standards/ Prominence of Impulsive Sounds.

This software will anaylsis the measurement for implusive characters by calculation and produce an excel report with an Adj Ki dB correction, including adding markers for each impulsive event calculated.

An Excel Report is then automatically produced, with the greatest level difference event highlighted