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Each method uses its own procedure for rating noise spectra based on the series of curves
associated with the method. The so-called "tangency method" plays a central role for
NC and related measures; the rating is effectively determined by the highest NC curve
"touched" by the spectrum. The frequency band that touches the highest curve (the most
dominant noise band) is indicated as part of the rating, e.g: NC-53(125Hz).
A full description of the rating procedures is beyond the purpose of this manual. Please
consult the corresponding standards for this information.
Carrying out a Noise Curves measurement is similar to an SPL or RTA measurement: set
the duration of the measurement and other parameters, and start the measurement.
Noise curves. In this example, the curves and rating for NC are displayed
During a measurement, the reference noise curves are shown as red lines. The actual meas-
ured spectrum is shown as a blue line. The cursor can be moved around to read the SPL at
any of the frequencies. The rating is shown, as well as the LAeq level.
Only one Noise Curves metric can be displayed at a time, but all metrics are calculated for
every measurement. If a measurement is saved, the saved file contains data for all noise
curve metrics. If you wish to evaluated more than one noise curve metric without measur-
ing more than once, this can be done as follows:
•
Select the first type of curves you wish to evaluate (e.g. NC)
•
Carry out the measurement.
•
Save the results
•
Now change to another type of curves (e.g. NCB)
•
Go to the measurement browser screen. NCB data will now be displayed
•
Repeat this procedure to inspect results for further metrics (RC, RCII, etc).
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