Acoustic camera

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Acoustic camera

Nor848B acoustic camera is a module based approach to acoustic camera that gives the user both portability and great resolution for a wide range of measurement situations.

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Nor848B acoustic camera is a module based approach to acoustic camera that gives the user both portability and great resolution for a wide range of measurement situations.

About

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Acoustic beamforming arrays, commonly known as acoustic cameras, enable the user to visualise different sound sources at different frequencies and source strengths. The resolution and ability to resolve sound sources spaced closely apart, and at lower frequencies, is mainly decided by overall size and number of microphones of the equipment being used. Although image manipulation and deconvolution techniques on the beamformed results might give added resolution, in practise the properties of the array still influence the results. This size versus resolution criteria is the crux of the acoustic camera market. Users want something that is small, light weight, and portable, while at the same time having excellent resolution, and the ability to go low in frequency. This has been an impossible demand for a single system – until now.

The Norsonic Hextile is a module based approach to acoustic camera that gives the user both portability and great resolution for a wide range of measurement situations. The array dish is based on a hexagon shape, given it both its name, and the ability to combine several tiles into larger systems.

Hextile – lightweight and portable

With a single Hextile, the user has a small, portable and lightweight acoustic camera that can be used for a wide range of measurement situations. The Hextile is a USB based acoustic camera, with a single USB cable for both power and data transfer – no extra battery cable needed. The array is made from robust and lightweight aluminium, has 128 MEMS microphones, and is less than 3 kg in weight while having a maximum diameter of 46 cm. The low frequency limit for the Hextile is 410 Hz.

Array geometry and beampattern for Hextile

Array geometry and beampattern for Hextile

 

 

 

 

 

 

 

 

 

Multitile – great resolution

For users that require better resolution both in lower frequencies and overall, three single Hextiles can be combined to a larger Multitile system, consisting of 384 microphones with a maximum diameter of 96 cm. The low frequency limit for the Multitile is 220 Hz.

Multitile – great resolution

Multitile – great resolution

Array geometry and beampattern for Multitile

Array geometry and beampattern for Multitile

 

 

 

 

Multitile (LF mode) – Low frequency measurements

For special low frequency applications below 1 kHz, it is also possible to utilise the Multitile in the low frequency configuration as the Multitile (LF mode). By placing the individual Hextiles further away, the maximum diameter of the complete array system is increased to 1.46 m, making it ideal for low frequency measurements. The Multitile (LF mode) is for low frequency measurements below 1 kHz, with a lowest frequency limit of 120 Hz.

Multitile (LF mode) – Low frequency measurements

Multitile (LF mode) – Low frequency measurements

Array geometry and beampattern for Multitile (LF mode)

Array geometry and beampattern for Multitile (LF mode)

Software Design

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The software design strategy has always had user friendliness and ease of use in mind. We want the user to be able to get results quickly, and start analysing recordings easily, thus spending time on the analysis, rather than the measurement set up or configuration of parameters. Live view of measurements combined with an intuitive software interface enables users without prior experience to make measurements within the first five minutes after powering the device.

Virtual microphone

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The one feature that really sets the software apart is the virtual microphone. The virtual microphone enables the capability to only get audio signals from the chosen listening point, and listen to sounds coming from specific directions of the video image, while suppressing noise and sounds emitting from other positions than what is selected. With this tool the user has the power of super hearing, and may gain more insight in addition to regular colour plotting of sources. Such super hearing may be especially useful in noisy and complex sound environments, where for instance different noise sources greatly impair the ability to distinguish which machinery is producing a faulty noise.

Advanced post-processing audio analysis

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In addition to live plotting and directive listening, it is also possible to record measurements and do the analysis at a later time. The raw signal from all microphones are then saved, and all parameters such as frequency selection, time selection and so on can be changed in post-processing. This means that a recording can be done without selecting the optimal parameters during the measurement, since these can be changed when analysing the recording. This also means that anybody can do the actual recordings themselves since it is then basically a matter of pointing the array roughly towards the area of interest and pressing record. All analysis and changes of parameters can be done in post-processing such as directive listening, graphical overlay of sources, spectrogram, FFT analysis and so on.

Acoustic eraser

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Sometimes sources may be closely spaced apart, or a strong noise source in the area of interest is interfering with the recording and impairing the image quality. Often this will be seen as either a single large source, or the source of interest will be completely shadowed by the stronger source. Seen in the image below is a situation where two equally strong sources are positioned close to one another, and the resulting colour plot will display a single large source. In such situations the acoustic eraser feature may prove valuable. This function will add a red circle to the screen that can be dragged to any point, and remove the source from that point. This is highly effective when several noise sources are present. As seen on the pictures the acoustic eraser completely removes the source where the suppress point button is positioned. The virtual microphone can further be positioned on the source of interest.

Acoustic camera acoustic eraser

Acoustic camera acoustic eraser

Acoustic camera acoustic eraser

Acoustic camera acoustic eraser

Order analysis

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Especially in automotive applications RPM measurements may give vital information. The acoustic camera software has the possibility to display frequency content as a function of RPM by using the order analysis function.

In the spectrogram window, frequency as a function of RPM is plotted. It is further possible to select a square in the spectrogram window to isolate interesting events. By pressing the “apply” button on the selection, the RPM and frequency limits in the main view window automatically change to the limits set by the selection in the spectrogram. The user may then find and interesting sound event in the spectrogram, and automatically get the corresponding colour plotting of the event chosen.

Acoustic camera rpm

Acoustic camera rpm

Specifications

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Audio and video

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Connection: USB
Microphones: 128 MEMS microphones
Max sound level: 120 dB
Min sound level (system): 9 dBA
SNR per microphone: 65 dBA
SNR array (system): 82 dBA
Audio sampling rate: 44.1 kHz
Camera resolution: 2592 x 1944
Opening angle: 105°
Frame rate: 15 FPS
Operating temperature range: -40 to +85

Frequency response

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Per microphone (flat): 100 Hz – 20 kHz
Per microphone: -26 +/-3dBFS/Pa @1 kHz 94 dB
Spatial sensitivity Hextile: 410 Hz – 20 kHz
Spatial sensititivy Multitile: 220 Hz – 20 kHz
Spatial sensititivy Multitile (LF mode): 120 Hz – 1 kHz

Physical

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Dimension Hextile: 41 cm x 48 cm, Ø 48 cm
Dimension Multitile: 83 cm x 84 cm, Ø 96 cm
Dimension Multitile (LF mode): 126 cm x 121 cm, Ø 146 cm
Weight Hextile: < 3 kg
Weight Multitile: < 10 kg
Material: Aluminium
Power consumption: < 3 W

Half power beamwidth (HPBW)

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Nor848B Half power beamwidth (HPBW)

Max side lobe level, and mean side lobe energy

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Multitile-LF

Multitile-LF

Multitile

Multitile

Hextile

Hextile

Low frequency performance at 500 Hz

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The biggest improvement when going from a single Hextile to the two different Multitile configurations is best demonstrated on a low frequency source. Seen below are the results from recordings on a single omnidirectional noise source emitting pink noise, with the colour plotting being done when the input signals are filtered at 500 Hz. This should give a direct comparison of the low frequency capability of the different arrays.

At the top are the different array configurations used for the recordings, with a 128 element Hextile, a 384 element Multitile, and a 384 element Multitile (LF mode). The diameters of the array configurations are 46 cm, 96 cm, and 1.46 m respectively.

The second rows show the beampattern for the different array configurations at 500 Hz and 3 dB dynamic range. As can be seen the beampattern gets more narrow, thus giving better resolution, as the overall array size increases.

Lastly the plotting results from the three different array configurations recorded on a real noise source are shown with 3 dB dynamic. The improvement in terms of resolution and pin-pointing the source is clearly visible when using bigger equipment.

Array geometry, beampattern at 500 HZ, and plotting results of pink noise source for Hextile, Multitile and Multitile (LF mode)

Array geometry, beampattern at 500 HZ, and plotting results of pink noise source for Hextile, Multitile and Multitile (LF mode)

Downloads

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Brochurer

Product range catalogue

  • Product range catalogue -

    Norsonic_productrange_catalogue_web.pdf (9762.29KB)
    Released
    Download
Software

Nor848 Acoustic Camera

  • Norsonic Acoustic Camera - 4.6.1102

    Norsonic-Acoustic-Camera-4.6.1102.zip (0.23GB)
    Released 08/04/2024
    Download
Technical note

Acoustic Camera

  • Acoustic camera and beampattern -

    TN-acoustic-camera-and-beampattern.pdf (480.1KB)
    Released
    Download

  • Evaluating array resolution -

    TN-array_resolution.pdf (2849.38KB)
    Released
    Download

  • Beamforming algorithms - beamformers -

    TN-beamformers.pdf (429.48KB)
    Released
    Download

  • Sparse arrays and array health check tool -

    TN-sparse-arrays.pdf (717.35KB)
    Released
    Download

  • Array gain and reduction of self-noise -

    TN-array-gain.pdf (107.37KB)
    Released
    Download
Case studies

Acoustic Camera

  • Office noise leakage -

    Norsonic-acoustic-camera-case-study-office-leakage.pdf (1145.44KB)
    Released

    Norsonic Acoustic Camera
    Filming sound leakages in highly reflective office environment

    Measurements in office complex, Lier, Norway, April 2016

    Download

  • Breakout noise from café -

    Norsonic-acoustic-camera-case-study-breakout-noise.pdf (1373.75KB)
    Released

    Norsonic Acoustic Camera
    Filming breakout noise from café and concert venue

    Measurements in bar and bistro in Oslo, Norway, March 2016

    Download

  • Traffic noise in apartment -

    Norsonic-acoustic-camera-case-study-traffic-noise.pdf (1419.04KB)
    Released

    Norsonic Acoustic Camera
    Measuring impact of traffic noise in apartment living room

    Measurements in apartment Oslo, Norway, February 2016

    Download

  • Wall leakage test in lab -

    Norsonic-acoustic-camera-case-study-wall-leakage-test.pdf (842.03KB)
    Released

    Norsonic Acoustic Camera
    Wall leakage testing in the lab with acoustic camera

    Measurements in acoustic lab, England, November 2015

    Download

  • Interior caravan car noise -

    Norsonic-acoustic-camera-case-study-caravan.pdf (1452.74KB)
    Released

    Norsonic Acoustic Camera
    Using acoustic camera inside caravan car to find squeak and rattle noise

    Measurements in caravan car, Lier, Norway, October 2015

    Download

  • Structure born noise -

    Norsonic-acoustic-camera-case-study-structure-noise.pdf (1391.09KB)
    Released

    Norsonic Acoustic Camera
    Filming low-frequency structure born noise with acoustic camera

    Measurements in apartment building, Oslo, Norway, September 2015

    Download

  • Car window squeak -

    Norsonic-acoustic-camera-case-study-window-squeak.pdf (1022.84KB)
    Released

    Norsonic Acoustic Camera
    Identifying short time high pitch squeak noise from electric window in car door

    Measurements in car factory, Korea, July 2015

    Download

  • Apartment sanitary noise -

    Norsonic-acoustic-camera-case-study-sanitary-noise.pdf (1094.3KB)
    Released

    Norsonic Acoustic Camera
    Pinpointing low level sanitary noise in apartment building

    Measurements in apartment building in Oslo, Norway, April 2015

    Download

  • Modular walls -

    Norsonic-acoustic-camera-case-study-modular-walls.pdf (1004.67KB)
    Released

    Norsonic Acoustic Camera
    Finding acoustical weak points in room dividing modular walls

    Measurements in a conference hotel in Trondheim, Norway, November 2014

    Download

  • Industry tonal noise -

    Norsonic-acoustic-camera-case-study-low-frequency-tonal-noise.pdf (1701.28KB)
    Released

    Norsonic Acoustic Camera
    Identifying low-frequency tonal noise in windy and noisy conditions

    Measurements on LNG gas terminal in Stavanger, Norway, September 2014

    Download

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