OptiNav BeamformX User Manual
Contents
1. The frame rate may be slower if the CPU cannot keep up with this rate A process for creating a movie is to first store some interesting data in the Spectrogram and pause Position the play point in the Spectrogram at the start of the interesting time interval at the interesting frequency Close the Recording stack if one is open and press Play Buffer When the end of the desired segment is reached press Pause Stp Rc and then Save mp4 Do not let the play point reach the end of the Spectrogram and wrap because this would be recorded in the final movie Spectrogram Window The Spectrogram window Fig 3 displays the spectrogram for the previous 30 seconds or so The vertical yellow line with the three black dots shows the current time and analysis frequency band Clicking in the window causes the acquisition and playback to pause if they are running sets the time and frequency to the point that was clicked and updates the Display It may be useful to click on hot spots in the spectrogram and then look at the Display to isolate the time frequency and spatial location of loud sound sources Small adjustments to the selected point can be made using the arrow keys Using the arrows keys repeatedly faster than the Display can update can cause the Spectrogram to get lost and move to a random point Bug 2 The width and duration of the Spectrogram are controlled by the setting in the Startup dialog when acquiring new data W2. since it is not currently possible to continue reading a Log file once reading has been paused Log data stores the array data to a binary file bin If a valid folder is entered in the Settings parameter Folder for binary Log data file then pressing Log data creates a file with an automatically generated name and begins logging data to the file unless BeamformxX is paused The automatic name is the date and time in a format like 20151108 014843 bin If a valid folder is not entered then a file dialog is opened to enable the user to create a file location and the file is opened A timer starts when the file is opened If the timer reaches Settings Maximum duration of binary Log data file then the Log stops and the file is closed The timer runs whether BeamformxX is paused or not A useful way to manage log files is to maintain a run log and have a window open to the output folder sorted by date When Log data is pressed and a new file is created the automatic name perhaps just the time part can be typed or copy and pasted into the run log along with description information The small scrollbar next to Mute is the audio output volume control Mute should usually be selected when an array is connected because feedback is likely otherwise The box with the units m is the focus distance z in meters This is similar to focusing an optical camera The z value represents the perpendicular di
3. R P Dougherty R C Ramachandran and G Raman Deconvolution of Sources in Aeroacoustic Images from Phased Microphone Arrays Using Linear Programming AIAA Paper 2013 2210 2013 Troubleshooting BeamformxX Conditions symptoms and corresponding suggestions are listed below Attempt to run Beamformx with no 64 bit Java installed in computer An error message pops up and Oracle s manual Java installation web page is opened http java com en download manual js Please install 64 bit Java Array connected and SIG software CcmAccess jar not installed G ema mm BeamformxX version 1 74 November 15 2015 SIG array connection software not installed OptiNav License Key 2535 Magnification of dialog windows 100 Data source File values below not used v U Frames per second suggest 9 8 max 98 jos 50 Buffer time seconds perhaps 30 Special function None Beamformx can still process previously saved binary data files Install SIG software to enable receiving data from to the array 22 Array disconnected and SIG software CcmAccess jar not installed opero voa BeamformX version 1 74 November 15 2015 SIG array connection software not installed No USB connection to array OptiNav License Key Zs Magnification of dialog windows 100 Data source File values below not used v Frames per second suggest 9 8 max 98 D Buffer time seconds perhaps 30 50 8 Special
4. function None BeamformX can still process previously saved binary data files Install SIG software and connect array to enable receiving data from to the array Software installed and array disconnected Loi Operating Mode e i Beamformx version 1 74 November 15 2015 No USB connection to array OptiNav License Key ZEZ Magnification of dialog windows 100 Data source File values below not used e Frames per second suggest 9 8 max 98 o s Buffer time seconds perhaps 30 50 BeamformX can still process previously saved binary data files Connect array to enable receiving data from to the array Check the USB cable 23 Software installed and array connected BeamformxX version 1 74 November 15 2015 OptiNav License Key Magnification of dialog windows Special function BeamformxX should be able to use the connected array or process previously recorded data depending the Data source choice Software installed array connected camera found attempt to use connected array failure receiving acoustic data from array i mme a Array exception CcmException from open CCM_ERR_DISCONNECTED g Try reinstalling SIG software If this does not resolve the problem contact your supplier for support 24
5. 0 2 m from the microphone array which has an aperture of about 0 3 m The Rayleigh limit for this case corresponds to a frequency of 20 kHz Frequency study The battery tire inflation unit shown in Fig 5 It is investigated at several frequencies in Figs 10 13 From this viewpoint the sound appears to originate from the center of the unit at 537 Hz Fig 10 from the left rear corner at 3955 Hz Fig 11 from the fan in the right rear corner at 8837 Hz Fig 12 and from the fan some gaps in the case and a switch at 16 650 Hz Fig 13 17 Figure 10 Battery tire inflation unit at 537 Hz Figure 11 Battery tire inflation unit at 3955 Hz 18 8837 9 Hz 0 5 m RAFB Figure 12 Battery tire inflation unit at 8837 Hz 16650 4 Hz 0 5 m RAFB Figure 13 Battery tire inflation unit at 16650 Hz 19 Angle study In order to examine the noise emission of the battery tire inflation unit as a function of radiation angle the microphone array was placed on a rolling cart and slowly rolled around the automobile accessory while keeping the array facing the unit Results for 8935 Hz are shown in Fig 14 20 Figure 14 Angle study of the battery tire inflation unit at 8935 Hz References 1 R P Dougherty Functional Beamforming Berlin Beamforming Conference BeBeC 2011 2014 2 R P Dougherty Functional Beamforming for Aeroacoustic Source Distributions AIAA Paper 2014 3066 2014 3
6. 9 6935 5 45 80 75 70 18 5 327 5 0 540 0 848 3 000 2015 10 06T17 05 11 916 6 765 8935 5 45 62 75 51 17 7 325 6 0 540 0 788 3 000 2015 10 06T17 05 12 022 fi 6 868 8935 5 45 19 75 08 Lat 325 6 0 540 0 788 3 000 2015 10 06T17 05 12 125 6 969 6935 5 45 29 75 17 18 5 327 5 0 540 0 848 3 000 2015 10 06T17 05 12 226 7 178 8935 5 45 29 75 18 18 5 327 5 0 540 0 648 3 000 2015 10 06T17 05 12 435 _ 7 278 8935 5 45 71 75 60 18 5 327 5 0 540 0 848 3 000 2015 10 06T17 05 12 535 7 278 8935 5 45 99 75 88 17 7 325 6 0 540 0 788 3 000 2015 10 06T17 05 12 535 kl 4 m gt i Figure 7 Peak list Show date Controls whether a string indicating the absolute date and time of each frame appears at the bottom of the Display 13 Show time Controls whether the time since the start of the array session is shown in seconds in the lower left corner of the Display Show peak level Controls whether the highest level in the display or in the ROI if one is present is shown in the upper right corner of the Display Show integrated level Controls whether the integrated level in the display or in the ROI if one is present is shown in the upper right corner of the Display The integrated level is the log sum of the values of the pixels in the display or the ROI It can be used as a rough estimate of the total contribution of an extended noise source It is not normalized to account for peak spread The appropriate normalization for most frequencies is t
7. OptiNav BeamformX User Manual November 16 2015 Applies to Version 1 75 of BeamformX Contents OVEN VIGW EEE E E A E AN A EA E E E A E EEEE 3 Startup Dilo TEE 3 n dee RTE TEE 5 Spectrogram Window cccsessssccececeesessaesecececesseeaaesecececessesesaeeececsseeseeaeaeceseceseesauaeaeeeessusseseuaeaeeeesssesesenaeees H Spectrum WHA OW EE 9 DISPIAY WINDOW E 10 Settings ET 11 Decay ln ernieren eree e r ae eae e aeaaee ae eE e ae a Ra REEERE 11 Microphone for spectrum and sound L 4091 11 Camera Pan and Camera Tilt sscsceccsiscccied ais edd EE E 12 Camera RESOLUTION esitage a a E a E A E EE 12 Slow Motion Playback Factor sseni ienie aeee beanie NENE EEE EEE TEE REN 12 Dynamic range for Auto Scale rolls of below 4 kHz 12 Magnification of Display Spectrum Spectrogram cscccsssccssscecssececssecesseccssececsaecesseecsseeceaececaaeceeees 12 Color tal eege eege EE EE E E E IR 12 Beam orming Elte te VE 12 Folder for binary Log data file auto name using date and time ccecccssececseseceessaeeeessaeeeeseaaes 13 Maximum duration of binary Log data file c cc ccccccccssssseceeecessessaeeeeeeeceeseseseseeeessessesneaeeeesesseseegs 13 Active FOCUSING for le 13 Wig UA e 13 SHOW EE 13 SNOW lt EE 14 Show TE EE 14 Show e MIT 14 Use of integrated level to determine reflection Coefficient 14 Resolution Ee E 16 PREC LISI Tee o UE 17 AN BIG SCUGY EE 20 REFERENCES ii iin a eNEEENE AEN EEE EES EES ER Troublesho
8. dialog Decay Time The acoustic outputs the columns of the Spectrogram the Single mic spectrum and the Display have memory that decays exponentially with the Decay time Setting the Decay time to a short value such as 0 01 sec gives displays that change rapidly with transient events such as echoes of impulsive sounds Setting it to a long time such as 1 sec gives results that are steadier and produces better averaging for stationary sources A compromise choice of 0 2 or 0 3 sec can give good results for common situations such as slowly moving people or vehicles Microphone for spectrum and sound 1 40 The selected microphone is used the audio output the Spectrum and the sound for MPEG 4 output If an ROI is present on the Display then focused data for the center of the ROI is used for all of these instead of the selected microphone 11 Camera Pan and Camera Tilt These angles compensate for any small misalignment of the camera within the array For a new phased array or an array that has been disassembled so that the camera may have been moved Camera pan and Camera tilt should be adjusted with a compact acoustic test source until the beamforming spot aligns correctly with the optical video image of the source Camera resolution discussed below must be set before adjusting Camera pan and Camera tilt Increasing the Camera pan and Camera tilt causes the acoustic spot move to the left and downward respectively in the Display O
9. ent spots from becoming too large If Auto Scale is not selected then the ends of the color scale are mapped to the Min and Max levels Success in this mode usually requires OptiNav BF to be selected Clicked value dB is an output that shows the level of a pixel on the Display that is clicked upon Settings brings up the Settings dialog Pause causes the display to stop updating and data to stop being added to the Spectrogram and the binary Log file and the Recording stack if either of both of these are in use The button is then disabled If Beamformx is reading a binary Log file when Pause is pressed then in addition to the other Pause functions the Log file is closed In the case that an array is connected Pause causes the Resume button to be enabled Play buffer causes the display to begin being updated from the data in the Spectrogram buffer starting from the time of the spot selected in the Spectrogram and tuned to the frequency selected in the Spectrogram If the Spectrogram is full and the play point reaches the end then Play continues wrapped to the start If the Spectrogram is not full and the play point reached the end of the data then Play stops Resume causes the data to continue being added from a connected array and data to resume being saved in the Log file and or the Recording stack Resume is not applicable when the Data source is File
10. hen playing recorded data the Spectrogram settings are determined by the Startup dialog when the recording was made The color scale of the Spectrogram Window runs from the Bottom Level the Top Level which are set using scrollbars in the Control dialog The color Look Up Table is chosen in the Settings Dialog ES pea k q gt ecl Soe 526x532 pixels RGB 1 1MB Figure 3 Spectrogram window The vertical yellow line with the three black dots represent the beamforming frequency band 1 12 octave in this case and time Spectrum Window BE KAL Te 29941 41x138 66 pixels 480x306 8 bit 143K 10000 15000 20000 Figure 4 Spectrum window The Spectrum window Fig 4 usually displays the narrowband spectrum from the individual microphone chosen in Settings Microphone for spectrum and sound 1 40 If a Region Of Interest ROI is present on the Display then the Spectrum shows the result of steering a subset of the array microphones to the point represented by the center of the ROI Outer microphones of the array are used to improve the resolution The buttons on the bottom of the Single mic spectrum cause the currently displayed spectrum to be Listed Saved in a text file or Copied to the system clipboard respectively Clicking in the spectrum window causes the analysis frequency to be set to the frequency that was clicked This is equivalent to adjusting frequency from the Control dialog If acquisition playback i
11. hone array need not be connected and the dialog elements below the choice are not used The Choose camera box specifies which optical camera is to be used for the reference video For a laptop computer the correct choice is usually 2 because the computer s internal camera is number one and the camera that is built into the microphone array is number two When using a desktop computer with the array the correct choice may be 1 If the optical image that appears in the Display seems to be originating from the wrong camera then you should exit BeamformX by closing the Display or the Control window and restart with different camera choice The Frames per second entry determines how rapidly the Display is updated and the time represented by each column of pixels in the Spectrogram Only certain fame rates are supported BeamformX will choose the allowable frame rate that is closest to the entry that is input in the box The maximum frame rate is 98 actually 50 000 512 97 65 fps Choosing a lower frame rate will increase the buffer time that can be stored in the Spectrogram because the maximum width of the Spectrogram is limited The recommend rate of 9 8 fps is convenient and usually sufficient The optical camera speed is limited to 30 fps choosing a higher rate may cause some the images from the camera to be used more than once The computer CPU speed limits the real time processed frame rate to 7 16 fps Using a faster computer and ch
12. ing it produces the conventional algorithm Frequency Domain Beamforming FDBF The conventional algorithm shows actual acoustic sources along with many spurious artifacts RAFB suppresses the artifacts and also runs about twice as fast For the most part the option of not checking OptiNav BF is only provided to show how bad FDBF is by comparison The exception is that FDBF can be more stable in showing marginal sources This mode should only be used if it is clear which spots are real The Freq scrollbar and textbox set the center analysis frequency and cause a Display update if the system is paused This frequency is the currently the center of a 12 octave analysis band A future option for 1 3 OB is planned Changing the frequency with these controls does not force a pause The Time scrollbar forces a pause and adjusts the playback time in the Spectrogram The Min and Max scrollbars set the lowest and highest levels respectively shown on the Display the Spectrogram and the Spectrum The Auto Scale checkbox controls how the upper and lower level of the color map in the Display are set If Auto Scale is selected then the highest level shown is mapped to the top color and the bottom color is set below the top by the amount Dynamic range for Auto Scale that is set in the Settings dialog Exception for frequencies below 4 kHz the dynamic range is gradually reduced as the frequency goes down to prev
13. name using date and time See Control Log data Maximum duration of binary Log data file See Control Log data Active Focusing for ROI This controls the time domain beamforming that is applied to isolate sounds from the center of the Region Of Interest if an ROI has been created on the Display If Active focusing for ROI is not selected and an ROI is present then conventional delay and sum beamforming is applied for the Single mic spectrum the Spectrum and the audio playback If an ROI is present and Active focusing for ROI is selected then a signal processing technique is applied to attempt to better isolate the sound source at the center of the ROI This processing makes the assumption that there is a distinct source at the center of the ROI If this is not the case and there is no source at the center of the ROI then Active focusing for ROI should not be selected because the signal processing algorithm is not well suited to producing silence Tabulate peaks Enables logging peak values from the Display in the table Peak list Fig 6 The information can be saved in a text file and copied to the system clipboard for pasting into a spreadsheet E x L Peak list Sox File Edit Font EE EE 6 8935 5 5 0 3 2015 10 06T17 0 e BLL 6 360 6935 5 45 68 75 56 18 5 327 5 0 540 0 848 3 000 2015 10 06T17 05 11 617 6 452 6935 5 45 70 75 58 18 5 327 5 0 540 0 848 3 000 2015 10 06T17 05 11 709 6 65
14. nce these values are set is should not be necessary to change them Camera Resolution This is the reciprocal of the focal length of the optical camera expressed in milliradians per pixel at the center of the image It should be set at the factory In case in needs to be corrected there are two methods for determining it One is to position a ruler in front of the array at a known distance capture an optical image from the Display and import it into an image analysis program such as ImageJ Using a small portion of the ruler near the center of the image determine the subtended angle in radians and the corresponding interval in pixels Take the ratio of these values and multiply by 1000 The other approach is to slowly move an acoustic point source across the field of view and adjust the Camera resolution by trial and error until the acoustic spot and the optical image of the source move at the same speed in the Display If there is an offset between the two images then the offset should stay constant over at least the middle 2 3 of the Display Once this offset has been controlled to be constant by adjusting Camera resolution it can be dialed to zero by adjusting Camera pan and Camera tilt Optical distortion in the camera lens may cause the optical locations to be slightly misaligned from the acoustic map near the edges of the map Slow Motion Playback Factor Set this value to 1 for normal operation When playing a rapidly changing scene from
15. o subtract about 30 dB Use of integrated level to determine reflection coefficient Figures 8a amp b show a setup with a speaker on a stand and piece of form rubber on the floor to partially absorb the reflection In Fig 8a the ROI surrounds the speaker and the integrated level of the speaker at 6 kHz is seen to be 85 dB In Fig 8b the integrated level of the reflection is 67 9 dB The relative level of the reflected wave is 67 9 85 17 1 dB at this frequency The reflection coefficient is therefore 17 1 10 10 0 019 These figures also show the date time and peak level annotations and an absolute level color scale Auto Scale not selected 14 E ee Display 102 reflectionData bin Figure 8a Integrated level of a speaker source 85 dB 15 zi Display 102 reflectionData bin Figure 8b Figure 8a Integrated level of a reflected image of a speaker source 67 94 dB Resolution study A resolution example is given in Fig 9 A thin metal plate has two holes that are separated vertically by 17 mm A turbulent wall jet is present on the back of the plate so the holes act as incoherent point sources A SIG ACAM 100 with an aperture of approximately 0 3 m is positioned parallel the plate with z 0 2 m With this setup the Rayleigh resolution equals the 17 mm source spacing at a frequency of 20 kHz Figure 9 shows beamforming images cropped from the Display of BeamformX for fou
16. oosing OptiNav beamforming are factors that tend to increase the maximum real time rate If the selected frame rate is too high for real time display then the display is updated as fast as it can be and the data is still entered into Spectrogram buffer at the full rate By pausing the acquisition choosing a Slow motion playback factor gt 1 from the Settings dialog and playing the buffer it is possible to revisit the data in slow motion so that every frame can be processed The Buffer time input requests a certain duration for the Spectrogram buffer If the requested time multiplied by the selected frame rate would make the width of the Spectrogram window exceed a preset limit then the time is reduced to stay within the limit The Special function text box can be used to install an optional feature by entering the name of the feature Clicking OK causes BeamformxX to either prompt for and open a binary file or connect to the microphone array as chosen and then display the Control Spectrum Spectrogram and Display windows Control dialog coma em oaa 992 227 sec 38 dB 15 dB Auto Scale Clicked value Settings Pause Log data OptiNav 1 50 m M OptiNav BF Peaks Rec BF Figure 2 Control dialog The most important control on the control dialog is the checkbox OptiNav BF Checking this selects the OptiNav beamforming algorithm Robust Asymptotic Functional Beamforming RAFB Deselect
17. oting BeamtormN 22 Attempt to run BeamformxX with no 64 bit Java installed in computer 22 Array connected and SIG software CcmAccess jar not installed cccsssscececessesssseaeeeeeeesesseaeeeeeeeens 22 Array disconnected and SIG software CcmAccess jar not Ipnstalled 23 Software installed and array disconnected ccesccessccesssecssseeceseeesuecssseecsensessueessaaecseesesseessseesesaeesees 23 Software installed and array connected ccececssssecececeseeseneaeeeeecesseseaaeaececeessseseaseseceesesesesneaeeeeeeseeeeea 24 Software installed array connected camera found attempt to use connected array failure receiving ACOUSTIC data om aray E 24 Overview Beamform x is a real time acoustic beamforming program from OptiNav Inc See www optinav com or contact Robert Dougherty at rpd optinav com It maps acoustic source distributions for noise control engineering machinery troubleshooting bioacoustics aircraft tracking architectural acoustics security and other applications It is based on OptiNav s beamforming algorithm Robust Asymptotic Functional Beamforming but can also perform conventional Frequency Domain Beamforming It displays the real time beamform map a spectrum a spectrogram and a text peak list The previous 30 seconds or so of data are stored in the spectrogram buffer The real time acquisition can be paused and the data in the spectrogram buffer can be replayed with different processing parameter
18. r frequencies and four settings FDBF FDBF Peaks OptiNav BF and OptiNav BF Peaks Auto Scale with a 10 dB dynamic range was used At 7 4 kHz top row of Fig 9 the frequency is too low for the sources to be separated but OptiNav BF does show the pair more sharply than FDBF The Peaks option for both methods shows a single spot in between the sources At 8 3 kHz second row the results are similar to 7 4 kHz except that OptiNav Peaks is able to separate the sources and shows two spots at the correct locations This illustrates the superresolution of the OptiNav method At 12 2 kHz third row both OptiNav and OptiNav Peaks resolve the two sources FDBF still cannot Finally at 19 4 kHz FDBF is able to separate the sources This occurs a little before the 20 kHz Rayleigh frequency because the Rayleigh limit is conservative Although FDBF does show two peaks they are not precisely at the correct locations In practice the Peaks checkbox can sometimes be used to identify distinct sources that are not seen individually in the continuous map It should only be used with OptiNav BF selected Applying Peaks 16 without OptiNav BF especially with HDR selected tends to highlight a large number of sidelobes i e misleading artefacts FDBF OptiNav FDBF Peaks OptiNav Peaks o BOG 12 2 kHz 19 4 kHz Figure 9 Resolution demonstration Two incoherent point sources are separated vertically by 17 mm and are located
19. s including the central frequency the focus distance and the temporal decay time Video with audio can exported to MPEG 4 files Raw data can be recorded for post processing using BeamformxX other software The four main windows are Control the Spectrogram the Spectrum and the Display Their functions and controls are described in the following sections after a description of the Startup Dialog Startup Dialog r EN e mm fe 4 Operating Mode BeamformxX version 1 71 November 9 2015 OptiNav License Key Magnification of spectrum and dialog windows 100 Data source Connected array Choose camera 2 for laptop Frames per second suggest 9 8 max 98 Buffer time seconds perhaps 30 Special function Figure 1 Startup dialog A sample Startup dialog is shown in Fig 1 The OptiNav License Key is required to verify that BeamformX is licensed to the particular microphone array If the License Key is not correct then a subsequent dialog will give the array serial number and instructions for contacting OptiNav Inc to obtain a license key Magnification of spectrum and dialog windows controls the size of the Spectrum window and the dialog windows this one on subsequent runs and the Settings dialog Data source is a choice between Connected array and File values below not used Choose the second option to post process a previously recorded binary file bin In this case the microp
20. s paused then the Display is updated to the new frequency If playback is running then unlike the case of clicking the Spectrogram window the acquisition playback continues with the new frequency It can be useful to click peaks on the spectrum to investigate their origins in the Display Display window Figure 5 Display window The Display window Fig 5 gives the beamform map overlaid on the optical video image The currently selected frequency and focusing distance are given in the upper left corner If OptiNav beamforming is selected then the text in the upper left corner also shows RAFB for Robust Asymptotic Functional Beamforming The legend for the color scale is shown in the lower right corner 10 Settings dialog Decay time 0 01 10 Microphone for spectrum and sound 1 40 Camera pan Camera tilt 27 Camera resolution 1 87 Slow motion playback factor gt 1 1 for normal speed Dynamic range for Auto Scale rolls off below 4 kHz i Magnification of Display S Magnification of Spectrogram Magnification of Spectrum S 2 T TO hoo co E Color scale Rainbow v Beamforming bandwidth 1 12 Octave Band E Folder for binary Log data auto name using date and time C Users Bob Maximum duration of binary Log data file s 5 l Active focusing Tabulate peaks V Show date V Show time Iw Show peak level Show integrated level _0K Cancer Figure 6 The Settings
21. stance between the array plane and the source plane for the beamform map Note that z is not the distance measured radially between the center of the array and a source point Let the radial distance denoted r Then z r cos where is the angle between the array axis and the ray from the camera to the source point Accurate specification of z is only necessary if the source plane is very close to the array say less than 1 m Given the 0 3 m aperture of the SIG ACAM 100 a z value of 3 m should be accurate enough for any actual source plane distance between 1 5 m and infinity OptiNav BF was described above Peaks with OptiNav BF deselected causes local peaks in the beamform map to be shown in isolation At high frequency this tends to highlight many sidelobes Peaks with OptiNav BF selected creates selects a superresolution algorithm within RAFB Rec BF causes frames that are shown in the Display to be added to an output stack entitled Recording Audio is also added to an internal audio buffer The label of Rec BF changes to Stp Rc and pressing this stops the recording When data is present in the Recording stack it can be used to create an MPEG 4 6 movie file by pressing Save mp4 and creating the output file name when prompted Closing the Recording stack clears the buffer The target frame rate for the mp4 file is Frames per second Slow motion playback factor
22. the Spectrogram buffer the playback in the Display can by slowed by increasing the Slow motion playback factor to perhaps 5 Mute should be selected in this case Dynamic range for Auto Scale rolls of below 4 kHz See Control Auto Scale Magnification of Display Spectrum Spectrogram Self explanatory Color Scale This sets the color Look Up Table for the Spectrogram and the Display Red Hot is a thermal that is best for black and white reproduction of the results and colorblind viewers Rainbow is more colorful than Red Hot Fire is similar to Red Hot but like Rainbow shows low levels in blue violet Beamforming bandwidth This is a choice between Narrowband 1 12 octave band and 1 13 octave band The choice applies only to the beamforming results The Spectrum and the Spectrogram always show narrowband spectra The 12 width of the band is shown by the height of the vertical frequency line in the Spectrogram The fractional octave bands are approximations to the standard bands created by including several FFT bins At low frequency where the fractional octave bands become smaller than the FFT bins the proportional bands reduce to single narrowband bins The Narrowband bandwidth is 50 kHz divided by the transform length The transform length is 1024 or a smaller power of 2 if necessary to make the block length smaller than the reciprocal of the frame rate Folder for binary Log data file auto
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