Cirrus Optimus+, Instrument Handbook

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Page 26
Sound Level Meters – User Manual
5.1.3 Leq view
Shows you the Leq, Peak, LAE (SEL) and C-A values with a choice of A, C or Z frequency
weightings.
The C-A data can be used with the HML method for selecting hearing protection.
If the time weighting is set to impulse, the C-A function is replaced by LAeq,I (also known as
LAIeq).
When the instrument is set to the German language, an additional ‘Taktmaximal’ page is also
available.
5.1.4 1:1 octave band view
This view shows the noise levels divided into octave frequency bands. This can be used to aid in
the selection of hearing protection and for noise control applications.
Some models also have the capability to show NR and NC curves and resultant values.
5.1.5 1:3 octave band view
This view shows the noise levels divided into 1:3 octave (called ‘third-octave’) frequency bands.
This view can be used for environmental noise measurements and for noise control applications.
The 1:3 octave band view also provides Leq,LF (20 - 200 Hz) and LAeq,LF (20 - 200 Hz).
5.1.6 Tone detection
This is a capability displayed within the 1:3 octave view on some instruments.
Instruments with tone detection use either the ISO 1996-2:2007 simplified method or an
improved method developed by Cirrus Research, which is based on the ISO standard, extended
to include tones between bands, tones in outer bands and Z-weightings. The ISO method only
applies to overall data when measuring or reviewing, whereas the Cirrus improved method also
applies to instantaneous live values.
When a tone is detected, the band is highlighted in blue on both the graphical and numerical
pages.
The tone detection method can be set to either the Cirrus improved method (default setting) or
the ISO 1996 method in NoiseTools.