Figure 1: The “Tools -> Add-ins” menu is used to turn on HD Acoustic Camera.
A new workbook is added called “HD Acoustic Camera” (Figure 2) at the bottom of the Simcenter Testlab software interface.
Figure 2: Time history is shown in the upper left with its corresponding frequency spectrum shown in the upper right. If desired, the time and frequency can also be selected simultaneously from the colormap display in the lower left. The hologram of the sound field is shown over the camera image in the lower right.
The workbook can be used to analyze data acquired with either a condenser microphone array or from the Simcenter Sound Camera. After the workbook opens, select an array recording using the "Open" button located in the upper right corner. Select the *.bdd file associated with the recording.
The “HD Acoustic Camera” workbook contains four main parts:
Time: The upper left display shows the entire time recording of the microphone selected from the pulldown list immediately below it.
Frequency: The upper right display shows a Fourier Transform of the selected time duration.
Colormap: In the lower left display a time frequency colormap of the time signal is shown.
Hologram: The lower right will display a hologram superimposed over a photo of the test object for the selected time and frequency after the “Compute and Save” button is pressed.
It is helpful to change the time increment for analyzing data from the default one second to a finer number. For example, an increment of 0.1 seconds (Figure 3).
Figure 3: Set the time increment to a smaller value than the default one second.
Now the desired time duration can be selected by dragging a cursor from left to right in the upper left display as shown in Figure 4.
Figure 4: In the upper left display, select the time duration of interest.
In the upper left, select a time duration of interest. The Fourier transform of the selected time is shown in the upper right.
In the upper right frequency display, select a frequency to analyze. In Figure 5, the tone associated with a person whistling is selected.
Figure 5: Select the frequency range of interest from the spectrum displayed in the upper right.
After selecting the frequency range, click on the “Compute and Save” button located in the middle right. The hologram will be updated. In this case, the hologram shows the location of the person who is whistling.
It is also possible to select both the time and frequency for the hologram simultaneously in the colormap display on the lower left (Figure 6).
Figure 6: Draw a square in the lower left colormap to select the time and frequency range of interest simultaneously.
In Figure 6, the vertical stripes in the colormap are created by a person counting. There is one vertical stripe for each count. By selecting the appropriate time and frequency range, and pressing the “Compute and Save” button, the person counting is shown in the hologram.
The back-propagated sound can be listened to and viewed. In the upper left, select the time duration for listening as shown in Figure 7. Note that the audio playback will always reflect the full frequency range of the original recording, even if a limited frequency range is selected in the displays.
Figure 7: Click on the hologram to hear the sound originating from that location.
Use the slider bar in the lower right to increase the volume to hear the sound of the original recording.
Then click in the photo/hologram in the lower right. The sound changes to recreate the back propagated sound at the location selected. Clicking in the photo acts like a sound stethoscope! It is the sound played from the selected location.
The colormap also updates to show the character of the sound from the location selected. Notice that in Figures 7 and 8, that the talking (vertical stripes) or whistle (horizontal stripes) are prominent depending on where the hologram is clicked.
Figure 8: Click on the hologram (lower right) and the colormap updates (lower left).
A green cross appears on the selected location when clicking in the hologram. To listen to the original recording again, turn on the “Raw Data” checkbox below the hologram.
Questions? Email Scott Macdonald (firstname.lastname@example.org) or contact Siemens Support Center.
Interested in Acoustics? Check out the On-Demand Acoustic Seminars.