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What Do Sounds Look Like?

Soundglass System Enables People to "See" Noises


The Soundglass monitor. (C)CHUBU Electric Power Co., Inc.

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Japanese researchers have developed a revolutionary type of glass that can show visually how loud a sound is and which direction it is coming from on a transparent display. Unlike ordinary sound measuring instruments, the Soundglass shows information on sounds emanating from the area that can be seen through the transparent display. Its applications include monitoring noise at electric power plants and other facilities to check for anomalies.

Safe and SoundThe Soundglass was unveiled in October 2009 by Chubu Electric Power Company, construction firm Kumagai Gumi, and Yamashita Yasuhiro, professor emeritus at Shinshu University. Malfunctions in equipment or instruments at power plants often cause abnormal noises, so detecting these sound anomalies is a vital element in maintaining the safety and efficiency of the facilities.


The Soundglass device. (C)CHUBU Electric Power Co., Inc.

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Chubu Electric Power previously used ordinary sound measuring devices, but these pick up the sounds from 360 degrees around the point of measurement, making it hard to pinpoint where a specific sound is coming from. To overcome this difficulty, the firm teamed up with Kumagai Gumi and Professor Yamashita to develop a device that could visualize sound information and specify the direction of the sound source. In 2001, the NoiseCam, predecessor to the Soundglass, was completed.

The NoiseCam consisted of a sound-concentrating microphone and a digital camera. Images taken with the camera were combined with sound information including loudness, frequency, and direction and shown on a monitor. By visualizing the part of the images from where the sound was emitted it was possible to pinpoint the direction of the sound source. The sound-concentrating microphone consists of five microphones separated by several centimeters, and the direction of the sound source is specified by measuring and analyzing the lags between the times when the sound reaches each microphone. A circle centering on the direction from which the sound emanated is displayed on the monitor. The size of the circle indicates the loudness of the sound, so that the volume can also be understood visually. The frequency of the sound, meanwhile, is shown by the color of the circle, changing from red to blue with changes from high to low sound.

The first NoiseCam released in 2001 displayed only still images, but in 2003 the ability to display moving images was added. Next, whereas it previously took several minutes for the data collected by the device to be displayed on the monitor, a NoiseCam that could display information in real time was developed in 2007.


The NoiseCam real-time sound camera. (C)CHUBU Electric Power Co., Inc.

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Smaller and SimplerThe NoiseCam is already being used in inspections at Chubu Electric Power's power plants and substations, but the system is large and several people are needed to carry it around. To improve this situation, the partners developed the Soundglass, which eliminated the need to capture and display images. In place of a monitor, a transparent display is used, enabling the viewer to see the objects on the other side of the screen, from which the sounds are emanating. This greatly simplified the system and reduced the computing power needed to run it.

Whereas the real-time NoiseCam required a tower computer, the Soundglass can be operated with an ordinary laptop PC, and the system can be carried around by one person. The Soundglass can also be set to limit the frequencies shown on the display. A transparent full color display has not yet been developed, so the circles shown on the Soundglass display are always orange. If a transparent display capable of showing full color comes on the market, however, the developers hope to incorporate it into the system.

Chubu Electric Power and its partners do not currently have any plans to commercialize the NoiseCam and Soundglass systems, but they are determined to continue improving the technology in the years ahead. (February 2010)

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