B&K 2250 Light, User Manual

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CHAPTER 13
Tone Assessment Option BZ-7231 – 1/3-octave Method
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• Middle frequency range: includes the 1/3-octave bands from 160 Hz to 400 Hz with a
level difference for a detected tone greater than 8 dB
• High frequency range: includes the 1/3-octave bands from 500 Hz to 10 kHz with a level
difference for a detected tone greater than 5 dB
With BZ-7231 software, frequency ranges and the limit for the level differences in low, middle
and high range can be set by the user.
Tone assessment is carried out for all the measured frequency bands (including those below
25 Hz and above 10 kHz). The level difference limit is extrapolated from the low and high
range to cover the complete measurement range.
If tones are detected outside the range from 25 Hz to 10 kHz the quality indicator (yellow
smiley) indicates “Tone out of ISO range detected”.
ISO 1996-2, Annex D does not specify the size of the adjustment. In the default setting of the
BZ-7231, Brüel & Kjær has chosen to set the value to 5 dB.
Calculating the Level Difference Between One Band and the Adjacent Bands
BZ-7231 software calculates the level difference between a 1/3-octave band and two adjacent
1/3-octave bands with lower levels. The difference is calculated between the band in the middle
and the highest of the adjacent bands.
13.3 Setting up the Analyzer
13.3.1 Selecting the Tone Assessment Option
Tap the Main Menu icon and select Setup from the list of options. Under the Tone
Assessment parameters (on the full list of options) tap the Tone Assessment option and set it to
On , see Fig.13.2.
Fig.13.2
Setting Tone Assessment
option on