Octave Band Analysis with Ascent
QUESTION
Can Ascent be used to perform 1/3 octave analysis?
ANSWER
You can use band alarms to achieve 1/3 octave style analysis by creating power based band alarms at 1/3 octave intervals. Zipped example vbz export files containing suitable band alarms can be downloaded here for Hz or here for CPM.
Using the Band Alarms
Note: Although not strictly necessary we advise you to remove existing alarms from your selected location before applying the imported alarms.
Note: See the 'Storing Re-usable Components in the Library' section of the Ascent Software Reference Guide for more information about exporting and importing alarms as components (.vbz3 extension files).
- Open a schedule entry in Ascent and double-click the downloaded vbz3 library file (the file must be unzipped first). Confirm that you wish to import the file when asked. An example file containing 1/3 octave alarm intervals can be downloaded here for CPM or here for Hz.
The band alarms in the example file are set for velocity units and all thresholds are 1 mm/s rms. However, you will see what is effectively a third octave summary at the top of the spectrum plot.
Third octave analysis example one
The yellow highlighting indicates that the level in that band exceeded 1 mm/s rms. This threshold is arbitrary.
Example two
Changing the Band Alarms
Once you have plotted some data you can rescale and resize the band alarm display at the top of the chart by moving the mouse over a power band alarm and pressing and holding down the right mouse button.
- Drag up and down to change the size of the band alarm display area.
- Drag left and right to change the scale/range.
- Change the thresholds (alert, warning, danger) of a band by double-clicking a band to open the Alarm Band Editor. Reset the thresholds or add new ones by selecting a threshold and typing in new values.
- Change the font color of the band alarm text by selecting Options>Edit/Change Scheme. Scroll down the list to the Band Alarms folder and double-click Alarm Band Text within this folder to open the Font window. From here you can change the font, color, and size.
Note: More detailed instructions for editing alarms can be found in your Software Reference Guide.
Re-using the Band Alarms at Other Locations
Once the band alarms have been imported to one location you can store these alarms in the Ascent library for quick access. The library is used to store commonly used components so that they can be quickly retrieved and reused.
- To store the band alarms, right-click the alarm icon that was created in the navigator list after import and select Library>Add Selection to Library.
Full instructions on storing and retrieving items in the library can be found in your Software Reference Guide.
FAQ ID: 11791 Last Reviewed: 6 January 2011