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Sound field control technology that flexibly creates audible and inaudible zones

Sound normally propagates in all directions because of vibrations in the air. Multiple sound spot synthesis technology erases some of the sound waves so they are inaudible, making it possible to implement local sound synthesis, which can synthesize sound only in a specific direction, or multiple spot sound synthesis, which can syntyesize different sounds in multiple directions.

The basic mechanism is to use multiple loudspeakers to mutually interfere with the sound emitted by each loudspeaker. By calculating and reproducing the playback signal of each loudspeaker based on the wave equation, which represents the propagation phenomenon of sound waves, sound waves can reach only "audible areas" and cancel out sound waves that spread to areas defined as "inaudible areas".

The reason it is called "multiple spot" is that you can set up multiple audible locations. For example, suppose that normal loudspeakers are placed facing four different directions, and each loudspeaker plays back a different sound. Since the loudspeakers spread the sound not only forward but also in other directions, the sounds will mix with each other and become difficult to hear.

Using multiple loudspeakers arranged in a circle (16 channels for the prototypes) and multiple sound spot synthesis technology, different sounds are transmitted to four areas, and sound that travels outside the desired area are erased. This way, it is possible to make only certain sounds audible in certain areas. For example, you can make an area where only sound A is audible and an area where only sound B is audible.

By arranging the devices and control system, it is possible to transmit sound to not four areas, but to one area or many areas. We are also developing proximity area sound synthesis technology that can not only manage areas, but also make it so that sounds can be heard when a listener is close to a loudspeaker and become inaudible when the listener moves away.

Can transmit sound to a specific target area with high sound quality and precision. Because it does not use ultrasonic waves, there is no risk of health problems.

Before, there have been directional speakers that can also transmit sound in a specific direction by using ultrasonic waves. They can transmit sound using the properties of ultrasonic waves, which have high directionality (the property of propagating in a specific direction).

Ultrasonic arrays often have sound distortions and skipping, and they emit loud sounds of over 150 db that cannot be heard by humans. There are concerns that they can harm human bodies and affect animals that have a wide range of hearing.

Multiple sound spot synthesis technology does not reduce sound quality because it plays sound sources through speakers normally. In addition, because it's not loud, it doesn't harm humans' health or affect animals.

We have made a prototype that is as small as about 18cm.
If you would like to try it out, please contact us.

Multiple sound spot synthesis technology is used with multiple loudspeakers arranged in a circle or straight line. We are working to make loudspeaker arrays as small as possible so that they can be easily installed in even more locations.

The photo shows a prototype of a small circular loudspeaker array that was developed in cooperation with Kitanihon Onkyo, Co., Ltd. It has a diameter of about 18cm and consists of 16 loudspeakers with a diameter of 3.2 cm arranged in a circle. You can hold a multiple sound spot synthesis demonstration at our NICT Koganei headquarters. Please contact us if you would like to try it out.

The photo shows a linear array of 64 loudspeakers. Whereas a circular array can partition sound synthesis areas in a circular manner, a linear array can partition them horizontally.

We have prototypes that demonstrate our ability to make devices this small. Moving forward, we will work with our business partners to make them even smaller and further improve sound quality.

It can be used with multilingual voice translation technology used by VoiceTra and be managed in real time using a tablet. It can be used for an even wider range of situations.

It can be used with multilingual voice translation technology or other technologies and be managed using a tablet, allowing an even wider range of applications.

VoiceTra is an app that uses AI to translate speech into multiple languages and use speech synthesis to play it back in each language. The speech synthesis technology was developed by Okamoto in NICT, who also developed the multiple sound spot synthesis technology, and uses cutting-edge neural network technology to synthesize speech that sounds almost completely natural in real time.

As an example of a use case, an announcement or speech can be translated into multiple languages using multilingual voice translation, then converted into synthetic speech that is played back locally in many areas by using multiple sound spot synthesis. This way, listeners can hear the announcement or speech in different languages depending on where they are standing.

• VoiceTra is available for demonstration purposes. To use it for commercial use, please ask us for a separate consultation. We also offer consumer products and services that use VoiceTra.

It is also possible to manage synthesized sounds and the areas they are played in using a tablet or smartphone in real time. This makes it possible to move areas even if the listeners do not move.

The National Institute of Information and Communications Technology (NICT) is Japan's sole public research institute specializing in the field of information and communications. It promotes research and development in information and communications technology with a comprehensive point of view, from the foundations to practical use. It cooperates with universities, industry, municipal governments, other research institutes in Japan and abroad, and other organizations with the goal of spurring innovation and using the results of its research and development to widely contribute to society.