PRÜFTECHNIK VIBXPERT II, Руководство по эксплуатации

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4-15
VIBXPER
T II 05.2012
Sound spectrum: third-octave and octave level diagram
VIBXPERT makes the sound spectrum available for the display and
evaluation of acoustic signals. The signal picked up by the micro-
phone is broken down in the frequency domain into bands with a
constant relative band width (octave bands or third-octave bands). To
quantify the volume, VIBXPERT specifies the sound pressure level of
each band as well as the overall sound level. Depending on the overall
level, four evaluation filters (A, B, C, D) can be set to take into account
the human perception of volume. Since the sound pressure level is a
logarithmic quantity, a reference value is needed to calculate it. This
value must be entered as well.
The sound spectrum can only be selected for amplitude spectra
with the vibration acceleration, vibration velocity and vibration
displacement quantities, as well as for user-defined quantities.
Envelope spectra, order spectra and order-based spectra cannot be
converted into sound spectra.
Displaying the sound spectrum
To display an amplitude spectrum as a sound spectrum, proceed as
follows:
• Open the Display Setup for the underlying amplitude spectrum:
In the Multimode selection screen:
- Mark the measurement quantity for the amplitude spectrum.
- Press the MENU button and click on ‘Display Setup/Measurement’.
In the measurement screen:
- Press the MENU button and click on ‘Display Setup’.
• Select ‘Third-octave bar’ or ‘Octave bar’ for the graph type.
• Set the ‘reference value’ needed to calculate the sound pressure
level (for example, for airborne sound p
0
= 20 µPa = 2 x 10
-5
Pa).
Left:
Open Display Setup (Multimode)
Right:
Sound spectrum settings
Graph type, reference value, amplitude
scale
Results

Note