Filming Sound Leakages in Highly Reflective Office Environment

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A newly built office complex is designed with glass facades between the offices and the hallway. The glass facades include a glass door. Although the glass structures themselves have a sufficient sound reduction value, the sound insulation between office and hallway was measured at 19 dB, which was far below the sound insulation criteria for offices given in the regulations. It was therefore important to find out where any weaknesses were introduced in the overall structure.

Results

The first results from the initial recordings proved disappointing. Although it was possible to hear clear differences by using the virtual microphone, which enables the user to listen to specific points in the image, the coloring of sources was only seen on a glass facade standing perpendicular to the wall of interest, as seen on the left side in the image below. Clearly this was a strong acoustic reflection and not the main source itself.

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Download full story > Nor848Acasestudy-officeleakageweb

Nor848A Case study – Filming breakout noise from café and concert venue

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A combined bar, bistro and concert venue in the city center has been renovated with a great emphasis on acoustic noise dampening. Nevertheless, the venue is still getting complaints from neighbours close by due to breakout noise from the location, especially during late night concerts. The establishment consists of a bar and bistro on the ground floor, with the concert venue on the floor above. The concert venue has several windows facing the outside street and neighbourhood buildings, and it was desirable to pin point any acoustic weaknesses in these windows. Also it was of interest to see if the wall itself needed additional measures, or if the main source contribution came from the windows alone.

Download full story > Nor848A.case.study.breakout.noise

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Download full story > Nor848A.case.study.breakout.noise

Finding Acoustical Weak Points in Room Dividing Modular Walls

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A conference hotel in Norway is using modular walls to divide large halls into several smaller conference rooms. The rooms are divided by modular walls that provide several different opportunities for subdivision and multipurpose use of the large area spaces.

When measuring the sound insulation between adjacent rooms through the modular walls, the resulting value was found to be too low, and noise from one conference room could possibly disturb listeners at adjacent rooms.  The dividing modular walls cover large areas, and are as high as 7 meters from bottom to top, which makes intensity measurements with handheld sound level meters difficult.  The room dividers could have several weak points, which were not easily identifiable.  It was thought that identifying and fixing the weak points in the individual modular walls would help increase the overall sound insulation capabilities of the entire wall element.

Nor848A-0.4 measurements were performed, and the acoustic camera was able to locate several weak spots on the walls even though the range where differences could be discovered were for certain areas below 0.05 dB.

The virtual microphone of the Nor848A-0.4 was very helpful during live measurements whereby you can scan and listen to the desired spots in the image, and also filter the listening function to desired frequency range.  This made it possible to scan along edges and hear differences in frequency from different points.  A change in frequency may indicate a sound leakage.  Also by using the spectrogram function to get a visual representation of the spectrum of frequencies as they varied with time, one could further indicate a leakage at various parts of the walls.

Please click here to download this Case Study in PDF.

Identifying Low-Frequency Tonal Noise at an LNG Gas Terminal

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A large LNG gas facility (approximately 300m x 150m) producing 300 000 tons of LNG annually is situated in a terminal area with the nearest populated area at a distance of around 1 km. Within the gas production facility, a low frequency tonal noise at around 500 Hz is generated causing complaints from nearby neighbours. The tone imposes a more stringent noise requirement on the facility, forcing noise reducing actions being made on the source.

In addition to the tonal noise, the entire LNG gas facility is rich in noise emitting sources, including losing and loading of maritime vessels, which further complicates the source location of the single tonal noise source. Also the location of the facility at the coastal regions of the western part of Norway, ensures that windy conditions are frequent, with wind noise further impeding the quality of acoustic recordings.

Based on measurements with hand held sound level meters, the problem area was narrowed down to be a large pipe in the midst of the facility. However it could not be
determined if the emitted tonal noise was from the entire pipe itself, or if it originated at a specific part of the pipe. There was also uncertainty whether there existed multiple
sources within the pipe, for instance at both the base and top layer. In the worst case the noise insulation would have to be performed over the entire pipe length, which could have been a very expensive solution.

By positioning the center of the acoustic camera  towards the pipe and adjusting the frequency to display only coloring within the 500 Hz 1/3-band, the noise source was located within seconds, and the source producing the tonal part from the pipe was detected. Measurements from different measurement positions also confirmed the source location.

By placing the virtual microphone on the localised source and using the spectrogram function, it was easy to verify the position of the source emitting a tone at 460 Hz.
Although the measurement location had quite windy conditions, the wind noise did not affect the measurement results at all. Wind noise can be viewed as spatially white, which means that wind noise sampled at different places in space, as is done with the Nor848A, is not correlated from position to position. When many different signals from many microphones are added in the beamforming algorithm, the wind noise will be added out of phase and attenuated proportional with the number of microphones being used.

With the acoustic camera it was possible to detect the tonal sound of the most crucial parts of the turbine. This meant that the facility could focus on and implement noise reduction actions in the right places.

After pin pointing the location of the noise source, further analysis could be made with measurements performed closer to the source of interest in order to further determine
the position and cause of the generated tonal noise.

Click here to download this Case Study in PDF.

Joint promotion of Acoustic Camera with Hiroki-san of Catec in Osaka, Japan

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Catec is the distributor of Norsonic in Japan. Catec is the leader in providing a wide range of high performance software for Vibration Measurement Systems, Noise Measurement Systems, Heat Measurement Systems, and Measurement Control Systems with RS232C and so on. Catec provides the general-purpose software like “Cat-System” and Virtual Test System. The Cat-System is utilized for measurement and analysis of vibration, noise, deformation, heat and so on by using general-purpose A/D board and Personal Computer. On the other hand, Catec also provides customized systems for various vibration, noise and heat analysis as well as technical consulting services.

Visit Catec website at http://www.catec.co.jp/aboutus.html

Sound tracing device. Small and good looking. Liked by the Monte Carlo of the Orient.

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Macao (or spelled “Macau”), a famous tourism and gambling city in Asia, has the second highest life expectancy in the world and is one of the very few places having a “very high Human Development Index” in Asia. It is thus not difficult to understand why there is a rapidly growing demand for better and better environmental quality from the citizens.

Due to its high population density, Macao’s roads and buildings are actually located very close to each other. When you stand on the streets, it is so easy to hear a very rich ambient soundscape, comprising sounds from the community, industrial, commercial activities as well as construction works. Due to its rich and complex nature, when people complain about the noise nuisance, sometimes it may not be easy to identify which source is actually the main one causing the problem using traditional measurement equipment.

When the environmental practitioners in Macao visited us during the MIECF 2014, after trying the Acoustic Camera Nor848A, they considered it a breakthrough as a sound chasing device that could be helpful for them to identify sound source, and very impressed by its portability and elegant appearance. Other visitors, coming from the sectors of aviation, transportation, environmental, energy, automobile and government, were introduced to various applications of Acoustic Camera Nor848A on product design, diagnosis, QA/QC and continuous improvement.  Special thanks to our Asia Manager, Michel!

It might be cool to generate a real-time dynamic noise map using a network of acoustic cameras. Hopefully in a not too distant future, we will be able to see a sound chasing device in every corner of the casinos, hotels and facilities in Macao!  Maybe we could use it to trace racing cars during the Macau Grand Prix!

Locating Sound with Norsonic Acoustic Camera

“Sound level meters do not provide information about where a sound is coming from. BKL has used the Norsonic Acoustic Camera 848 to identify the location of dominant industrial, marine, road, rail and indoor noise sources. It uses real time processing with 256 microphones mounted in a 1m diameter disc to perform this analysis. In this looped example, the location of a distant ship horn blast is obvious using the Nor848, illustrated with a sound contour overlay. Furthermore, the audio playback is specific to the cursor location so the listener can also “hear” the sound that is arriving from different directions.”

Source: BKL Consultants