Difference between revisions of "Sound Intensity Manual"

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Sound Intensity Manual (view source)

Revision as of 10:17, 29 June 2020

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==part2==
 
==Acquiring Sound Intensity & Sound Pressure==
Data acquisition is achieved with the '''Main Mode. '''The functions described hereafter can be accessed in two ways:
 
* The '''Control panel''' for the real time acquisition, placed in the left part of the screen
* The '''Acquisition menu''', functional to various real time measurements:
* Level calibration
* Phase calibration
* PRI Index
* Octave Band Real Time
* Narrow Band Real Time
 
[[Image:Acquiring_Sound_Intensity_part2_01.gif|framed|none]]
 
''Acquisition menu and control panel''
 
<br>So, data acquisition can be performed for two kinds of operations:
 
* System calibration
* Real time acquisition and analysis
The display mode and the commands are shared between the two applications.
 
===Calibration===
The calibration procedure can be divided into three parts:
 
* Pressure;
* Phase;
* Pressure residual intensity (PRI) index.
 
====Pressure Calibration====
The first and most common procedure is the one for pressure calibration.
 
The first step is to configure the calibrator type and the measurement chain from the Equipment Set Up menu. The procedure has to be adopted both for the microphones and the calibrator clicking the relevant fields and selecting the items from the database table. The transducer sensitivity will be updated according to the information stored for the equipment set-up.
 
Then the user has to fit the calibrator on one of the two microphones and activate it. Pressing the <font color="#0000FF">'''Start''' </font>button the program will activate the procedure. If the analyser has not been activated yet, the program will ask if the user wants to perform the operation at this time. Once the analyser has been initialised, the application will try to detect the signal and begins the automatic calibration procedure. If the <font color="#0000FF">'''Calibration detected''' </font>and the <font color="#0000FF">'''Level Matched '''</font>box lights up in red, pressing the <font color="#0000FF">'''Calibrate''' </font>button the software performs the stability check and the new sensitivity is suggested in a message box.
 
[[Image:Acquiring_Sound_Intensity_part2_02.png|framed|none]]
 
''Pressure calibration''
 
The user could accept the measurement results and this way transfer to the internal database the new value that will be used for the following measurement. It is convenient to verify the last accepted value starting again the acquisition, verifying that the <font color="#0000FF">'''Level Matched '''</font>box lights up in green. Fitting the calibrator on the other transducer it is possible to perform the calibration on the second channel.
 
The lower part of the window shows the corrected sensitivity history for each transducer. It is always possible, during the measurement, to recall the <font color="#0000FF">'''Instrument Set up''' </font>window clicking with the left mouse button on and change the instrument set-up varying the '''Range''', the '''Average Mode''' (linear or exponential) and the '''Average Time'''.
 
[[Image:Acquiring_Sound_Intensity_part2_03.png|framed|none]]
 
''Instrument set-up during calibration''
 
====Phase Correction====
This calibration type has to be performed using a white noise generator and a coupler to set the microphones in such a way as to put them in the same conditions with regards of the sound pressure waves. First of all fit the microphones in the calibrator coupler and plug in the cable connecting the analyzer to the generator. Then press the '''Start''' button in the "'''Built in white noise generator'''" section. The analyzer generator will then begin to reproduce a white noise at the level specified by the Built in white noise generator '''Gain'''.
 
[[Image:Acquiring_Sound_Intensity_part2_04.jpg|framed|none]]
 
''Phase calibration screen shot''
 
Press the '''Start''' '''White Noise Generator''' button to proceed with the calibration procedure. Then use the control panel to start the measure. Be sure pressure calibration has been performed before starting the procedure. Use linear averaging to obtain stable level. The time needed to perform the whole calibration process is about three minutes.
 
When the acquisition stops, it is possible to show the corrected intensity values by selecting the "'''Apply correction'''" tick in the instrument Set-Up window.
 
====PRI Index determination====
This procedure is very similar to the Phase correction process, but concerns with the setting up of the equipment and the data input for the pressure residual intensity index, related to the grade of accuracy the user wants to achieve.
 
In the case of real time procedure, fit the probe in the coupler of the calibrator, turn the pink noise generator on, set up the instrument in the '''Set up / Equipment '''menu (see next sections) and select the "'''Start"''' button in the Control Panel to start the acquisition. At this stage the software asks the user to select only one spacer with the full frequency span activated. This expedient has to be used only to perform this measurement the right way: a single spacer with a full frequency range in the actual environmental conditions is the status in which the calibration has to be done. After this step the user can set backward again the configuration of the spacers and their frequency ranges.
 
[[Image:Acquiring_Sound_Intensity_part2_05.jpg|framed|none]]
 
''Pressure - residual intensity index calibration''
 
The user should select a linear average of, at least, 60 – 120 seconds in order to obtain a meaningful PRI index. Pressing the "'''Accept'''" button, the data will be transferred to the internal database. The program will take these values into account during the sound power level determination. When the user accepts the measurement, the software proposes the following window:
 
[[Image:Acquiring_Sound_Intensity_part2_06.png|framed|none]]
 
''PRI confirmation area''
 
The application gives information about the status of the environmental conditions, just to make the user notified that the spectrum of the acquired data will be adjusted to normalize it to the standard condition and to the spectrum length required by the standard (25 mm). The spectrum will be saved, according to the check box selection, in the Analyzer Set-Up area and/or in the Analysis Set-Up Area. Please read chapters 5.1 and 5.2 to delve into application PRI management.
 
===Sound Pressure & Sound Intensity Acquisition===
Data acquisition is achieved with the '''Main Mode '''on (Cf. Section 2)
 
====Acquisition control panel====
Actions to operate the acquisition are achieved through the control panel interface.
 
Auto progress:
 
When it is pressed, the selection of the cells during the acquisition is done as defined in the sequencing path of the measured surfaces.
 
[[Image:Acquiring_Sound_Intensity_part2_07.png|framed|none]]
 
Octave band real time acquisition
 
====Real Time Octave====
The user can start the real time acquisition procedure by pressing the relevant button in the main interface window. This action will open the window shown.
 
Press the segment selection tool and choose a position on the measurement grid to import the data into it.
 
Press the Start button to begin the acquisition.
 
Press the Save button to store the data in the project structure.
 
[[Image:Acquiring_Sound_Intensity_part2_08.jpg|framed|none]]
 
''Octave band real time acquisition''
 
====Measurement Steps====
Before acquiring any data, the measurement surface is represented with a default colour. As soon as data is stored on a segment, a color is associated with it, showing immediately what segments have been measured and what segments have not.
 
[[Image:Acquiring_Sound_Intensity_part2_09.png|framed|none]]
 
====Measurement procedure====
1. Click on «&nbsp;'''Segment selection'''&nbsp;» for selecting a segment
 
2. Select a segment where the measurement will be carried out (the segment should become white).
 
3. Place the probe with the p-p axis perpendicular to the measurement surface as shown by the following figure.
 
4. Press '''Start''' (the selected segment should blink during the measurement). Please note that the analysis set-up should be done using a «&nbsp;linear average&nbsp;» so that the measurement stops automatically after a defined averaging time.
 
[[Image:Acquiring_Sound_Intensity_part2_10.png|framed|none]]
 
[[Image:Acquiring_Sound_Intensity_part2_11.png|framed|none]]
 
5. Press '''Accept''' to save the segment measurement
 
6. Press '''Reject''' if the measurement was not satisfying
 
7. If the measurement is satisfying go to next segment
 
8. If the measurement is not satisfying start the measurement again on the same segment
 
[[Image:Acquiring_Sound_Intensity_part2_12.png|framed|none]]
 
Shortcut keys as displayed on the above picture may be used in order to operate the software from the keyboard.
 
====Auto progress & Set-Up Shortcut====
By right click on the real time graph:
 
<nowiki>*</nowiki> You can activate the «&nbsp;Auto progress »&nbsp;function: If&nbsp;selected, pressing «&nbsp;accept&nbsp;» after a measurement will make the segment selection progress a step forward.
 
<nowiki>*</nowiki> You can also activate the «Instrument Set-Up» shortcut to change measurement parameters.
 
[[Image:Acquiring_Sound_Intensity_part2_13.gif|framed|none]]
 
''Auto progress and Instrument Set-Up shortcut''
 
====Remote control operation====
As often in Sound Intensity measurements, the system should be operated remotely from the PC. For this purpose, the GRAS and the Microtech Geffel remote control are configured to allow this. Two buttons operate in the same way as the '''Start/Stop''' and '''Accept/Reject''' as described above in the previous section and as represented by the following picture. In addition, 2 LEDS assists the operator. The first LED of the probe shows the measurement status: measurement running, waiting for accept/reject or stopped. The second LED shows if any overload has occurred: this information may help the operator in his decision to accept or reject the measurement.
 
[[Image:Acquiring_Sound_Intensity_part2_14.png|framed|none]]
 
====Narrow band Analysis====
In several cases it is very important to perform narrow band analysis to better understand noise causes. In this occurrence, an FFT analysis can be performed directly using the real time performances of the OR 25 PC Pack.
 
First of all the user have to click on the '''Real Time FFT Analysis''' button, placed in the upper part of the '''Control Panel'''. Then a new window opens, and the analysis starts as soon as the user clicks on the '''Start''' button.
 
To stop the acquisition, click on the '''Stop''' button.
 
It<nowiki>'</nowiki>s noteworthy that data acquired with this procedure can<nowiki>'</nowiki>t be stored in the project and then are not taken into account during sound power determination according to the ISO Standard.
 
[[Image:Acquiring_Sound_Intensity_part2_15.png|framed|none]]
 
''Narrow band real time acquisition''
 
====Overview grid====
The overview grid has been designed to enhance a number of points. In particular, the main one is to make the important information very visible from a distance. The overview grid benefits to the acquisition as well as the analysis.
 
It let the user:
 
* Improve greatly the visibility of the measured values such as the sound pressure, the intensity level or the power level through the surface of the selected cell. It is given either for a defined frequency or for the overall level.
 
[[Image:Acquiring_Sound_Intensity_part2_16.png|framed|none]]
 
''Overview grid''
 
* It shows clearly the geographic position of the measured point in "Meters". It is particularly useful for positioning the altitude of the measurement points.
* It gives also clearly the coordinate position of the measured cell in the surface.
* Finally a large progress bar is designed in order to make the evolution and status of the linear averaging very visible.
 
[[Image:Acquiring_Sound_Intensity_part2_17.png|framed|none]]
 
''Overview grid during acquisition''
 
The overview grid is activated by clicking on the following icon as shown by the red arrow on the next figure
 
[[Image:Acquiring_Sound_Intensity_part2_18.png|framed|none]]
 
''Showing the overview grid''
 
==Results & Noise Distribution Analysis==
The Analysis set-up is achieved with the '''Main Mode '''on.
 
There are four ways to display the results:
 
* '''Color display;'''
* '''Multi frequency view''';
* '''Parallel Space''';
* '''Off line Octave Spectrum'''.
===Color Display of pressure and intensity fields===
The display tools described in this section are available when the corresponding option was purchased.
 
Using the mouse left button and specific keyboard keys (Ctrl and Alt) the 3D displays can be handled as:
 
* Translating the display origin: Drag with left mouse click. The '''Origin translation '''icon must be toggled on''' '''(Cf. section 2).
* Rotate the display: Ctrl key <nowiki>+</nowiki> Drag with left mouse click
* Zoom the display: Alt key <nowiki>+</nowiki> Drag with left mouse click
===Visualization set up===
====Display modes====
There are seven display modes available to represent pressure and intensity fields:
 
[[Image:Acquiring_Sound_Intensity_part2_19.gif|framed|none]]
 
''Display modes.''
 
1. Monochromatic: useful to depict the measurement surface with the active measurement segment on (blinking);
 
2. Discrete: can be used during acquisition to differentiate measured segments from not yet considered segments;
 
3. Smooth: the easiest way to portray a continuous distribution of pressure and intensity fields over the geometry of the device under test. A linear interpolation order for the smoothing of the contours can be selected in the range 1-10;
 
[[Image:Acquiring_Sound_Intensity_part2_20.png|framed|none]]
 
''Smooth contour plot of the intensity field.''
 
4. Contour: with this option the user can plot equal-pressure and equal-intensity lines over the measurement surface. It<nowiki>'</nowiki>s also possible to select the step difference for two consecutive curves to increase the number of lines within the representation.
 
[[Image:Acquiring_Sound_Intensity_part2_21.png|framed|none]]
 
''Contour representation of the intensity field.''
 
5. Section: useful to display a single line pertinent to a specific pressure or intensity level. For example, in the following figure is represented the contour plot for an intensity level of 67 dB re 1pW/m<sup>2</sup>.
 
[[Image:Acquiring_Sound_Intensity_part2_22.png|framed|none]]
 
''Section representation of the intensity field.''
 
6. ISO Index: this mode is useful to represent the measurement surfaces complying or not complying the Standard requirements according to the selected accuracy of the determination. Complying faces are light up with green, not complying are light up with red.
 
[[Image:Acquiring_Sound_Intensity_part2_23.png|framed|none]]
 
''ISO Index view.''
 
7. Segment Status: the segment status view type has three functions:
 
* Segment status visualization and activation/deactivation: The segments can be activated for the use in sound power determination (green) or deactivated (red) in the case the user doesn<nowiki>'</nowiki>t want to use them during the sound power determination. The software will compute the Sound Power accordingly to the performed choices.
 
[[Image:Acquiring_Sound_Intensity_part2_24.png|framed|none]]
 
''Segment Status''
 
* Segments in which data were imported: the user can see at a glance the segments where data were imported (green cells).
 
[[Image:Acquiring_Sound_Intensity_part2_25.png|framed|none]]
 
''Segments in which data were imported''
 
* Spacer used for the measured face: this mode allows the user to display the spacers used for a measurement surface. Red segments have not been measured yet with any spacer, green segments have been measured with all the spacers defined for the project, and yellow segments have been measured with some of the available spacers. Scrolling the frequencies, the user can see the spacers used in the various frequency ranges with a specific spacer.
 
[[Image:Acquiring_Sound_Intensity_part2_26.png|framed|none]]
 
''Spacers used for the measurement surface''
 
====Display settings====
There are several display configurations the user can activate by clicking on the display area with the right mouse button. Basically there are three types of set up:
 
* '''dB scale''': if the user clicks on the dB (A) – linear selector, the graphs will display the chosen weighting.
* '''Frequency selection''': use this command to choose among the frequency bands the one you want to display. It is also possible to show the overall (frequency sum) values for each segment.
* '''Pressure – intensity''' layer: the user can display the relevant data related to the chosen frequency on the contour maps by selecting the pressure or the intensity layer.
====Color Scales====
By clicking right on the color scale the user activates the pop-up menu he can employ to select the different available types of color scale:
 
* '''Hot (fire)'''
* '''Cold (water)'''
* '''Absolute'''
* '''Rainbow (editable)'''
* '''Black and white'''
* '''Mono red'''
* '''Mono green'''
* '''Mono blue'''
The '''Rainbow''' scale is editable. To edit this scale click with the left mouse button on the color you want to extend. By dragging the cursor you will be able to increase or decrease the range of this color on the scale.
 
When you have finished editing your new scale the display will be automatically updated with the new color scale settings.
 
===Multi Frequency===
The '''Multi frequency''' spectrum view has been developed to show simultaneously several frequency plots in one shot.
 
[[Image:Acquiring_Sound_Intensity_part2_27.jpg|framed|none]]
 
''Multi frequency view''
 
To activate this command click on the relevant button and select the frequencies you want to show. Then click on the '''Next''' button and select the area you want to see in the multi spectrum view window. Click at first the top right point of the selection window and then the bottom right one. The program will open a new window showing the surfaces for the selected frequencies.
 
----
 
===Parallel Space===
Using the '''Parallel space''' outlook it is possible to show the same surface from different points of view. Select the command by pressing the relevant button. This action will open the new parallel space window.
 
[[Image:Acquiring_Sound_Intensity_part2_28.jpg|framed|none]]
 
''Parallel space sight''
 
Rotate and zoom the object in the parallel space window until you reach the desired point of view.
 
When the represented object is in the required position press the right mouse button to show the pop up menu and fix a parallel space.
 
From now on the usual representation and parallel space will be linked during pan, zoom and rotation operations.
 
===Off-line octave spectrum===
The '''Cell selection''' cursor has been developed to activate functions for a single cell:
 
* Display data for:
* Pressure
* Intensity
* P-I Index
This second command must be used with the dynamic cell spectrum button in the left part of the main window.
 
In any case the user has to point the cursor to the cell he wants to highlight and the spectrum will be updated according to the data stored for that particular segment.
 
To fix a particular segment just click on it. The segment lightens and the user will be able to move the cursor around the screen without changing the spectrum shown in the window.
 
To switch from a kind of representation to another (for example from pressure to intensity graphs) click on the window title with the right mouse button.
 
[[Image:Acquiring_Sound_Intensity_part2_29.jpg|framed|none]]
 
''Off-line spectrum mode''
 
Clicking with the right mouse button, it<nowiki>'</nowiki>s possible to have options for the Offline spectrum. For example, the options are:
 
- Bipolar intensity;
 
- Y-axis: Autorange, fixed unzoom;
 
- Label: intensity, pressure;
 
- Export image file (as bmp or metafile);
 
- Export data (as txt file).
 
==part3==
==part3==
==Sound Power using ISO 9614 Part 1==
==Sound Power using ISO 9614 Part 1==
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