Press Release Back Number(2005)

Seeing sound that cannot be heard! Low-frequency sound visualizing system developed
- A "sound" camera for low frequencies -

May 24, 2005
Chubu Electric Power Co., Inc.

We of Chubu Electric Power Co., Inc., jointly with Kumagai Gumi Co., Ltd. and Professor Yasuhiro Yamashita, Faculty of Engineering, Shinshu University, have succeeded in developing a system to identify the direction to the source of low-frequency sound* and visualize it on a display.

* Low-frequency sound refers to sound of 100 Hz or lower.

The "sound" camera, as a system to visualize sound, was developed and publicized by us for the first time in the world in 2001, and refers to a system that identifies the direction to the source of sound, intensity (sound pressure level in dB), and pitch (frequency in Hz), and visually superimposes this information on the display of a digital camera.

The present system we have developed can visualize low-frequency sound of 100 Hz or lower, which was not possible with the conventional type of "sound" camera. Low-frequency sound exists almost everywhere, and surrounds us even at home. It can cause headaches, dizziness, and a sense of heaviness, depending upon the individual, and may also vibrate doors and windows. Low-frequency sound spreads over a wide angle and can travel great distances, which makes it extremely difficult to identify the source. The ultra-low-frequency sound of 20 Hz or lower in particular is characteristic in that it cannot be heard by humans.

No precedent currently exists in the world for such a system that can, at a practical and quality level, identify and visualize the source of sound undetectable by the human ear.

This system has the following features.


  1. (1) Even where more than one source of low-frequency sound exists, it can identify the source, intensity (sound pressure level), and pitch (frequency) of the respective sound, subsequently displaying these in a visual form.

  2. (2) The applicable frequency range is from 10 to 550 Hz, which covers low frequencies of 100 Hz or less and therefore even as low as 10 to 20 Hz, which is undetectable by ear.
    (The corresponding range of the conventional "sound" camera is from 100 to 4,500 Hz.)

  3. (3) Both AC and DC power can be used, making it possible to use the system inside or outdoors. The system is compact and lightweight, and therefore is highly portable and easy to set up outdoors.

The present development has thus made it possible to identify the direction to the source, and characteristics, of low-frequency sound, which was a cumbersome process with conventional systems. Applications are expected to arise in a broad range of fields, such as taking soundproofing measures against noise from factories, traffic, and construction work.

We intend to verify the efficacy of this system by testing it in various sound environments.