28.07.2014 change 28.07.2014

New possibilities of sound recording

Sound engineers will have a system composed of wireless recording devices at their disposal. The system can process sound registered live so that the listener has the impression of being at the recording venue. The listener will be able to freely move on the sound stage, and move it. This is a general outline of the research and commercial AudioSense project.

The project received PLN one million funding from the LEADER programme of the National Centre for Research and Development.

According to the project leader, Dr. Tomasz Żernicki, CEO of Poznan\'s company Zylia, in the popular 3D audio systems we now have home theater, where the sounds come from several speakers - not just two, but five or seven - spaced around the listener. The sound source is where the speaker stands, it is stationary. In addition, the number of microphones used during the recording is closely linked to the sound reproduction method, or the number of speakers.

"In our system, recorded audio material can be played on any home theater system. In addition, the system will be fully interactive, allowing the user to freely manipulate sound sources" - explained Dr. Żernicki.

The system separates individual sound sources in space. If several people are talking to each other in a room, the "output" of the system will be recordings of particular speakers. In current sound recording systems, to achieve that you need to use several microphones, and later the recordings are mixed into a home theater sound. But you can not accurately separate signals - single spoken words or sounds. We do not know the exact location of sound sources. Each microphone records because a mixture of sounds. Poznań engineers also want to arrange microphones in space, but the desired output are individual sound sources and their spatial location.

"This gives us the ability to manipulate sound sources. We can freely change the location of each speaker (specifically his voice) in space. This makes the work of sound engineers very easy, because they do not have to de-mix the recording. Separate sound sources allow preparation of recordings so that users can move freely in three-dimensional sound stage. In addition, the user can record the spatial signal without specialized knowledge of a sound engineer" - said Dr. Żernicki.

The sound stage the researcher has in mind is the transfer of the source sound environment to the listening room. It is easy to understand when we imagine a concert, where the musicians stand on stage in certain spots.

Classic material prepared by sound engineer is static, we can not manipulate it. Home theatre systems offer good sound experience only when we sit in a particular place in the room. In the system created by the Poznań team of seven researchers, the user receives a particular sources of sound - drums, guitars, vocals - and their locations. When we listen to a concert registered this way, we can approach the sound source, we can move it freely in space, bring it closer or move away from each other the whole stage.

What are the applications of these technical innovations?

"Such capabilities are useful, for example, during a teleconference or in games. It is also a great convenience for TV, radio stations and film producers. They can create material that can be easily processed - described Dr. Żernicki. - Our system teleconferencing will allow to set up the microphones around the table and then extract only the recordings of those people who said something, at the same time identifying the speaker. The listener will be able to easily determine where exactly the person was sitting at the table, because the location will be recreated on the recipient’s end. If the selected speaker is located to the right, he or she will also be heard from the right."

Innovative systems often require developing special equipment that will offer new functionality. It will be the same in this case, but, according to the authors, the price of equipment will not be excessive. Prototype hardware is being developed in Poznań. Wireless devices are necessary in order to offer customers new quality of work with audio productions.

"Now we can set up a few or several microphones and record spatial sound. The problem is that it is a lot of equipment, each microphone connects to a recording device, and this, in turn, to a power source. The result is a web of cables. We are working on a system of wireless acoustic sensors, which operate on battery power" - says the CEO of the company Zylia, beneficiary of the National Centre for Research and Development grant.

Each acoustic sensor is equipped with two miniature wireless microphones, the size of a matchbox. Sound "comes" from all microphones via radio transmitters and "enters" a special compression device. Compressing audio is, in simple terms, processing of recordings so that they can be sent to the recipient.

"We try to be compliant with the current 3D sound compression standard MPEG-H 3D Audio. This compliance will allow the recordings made by our system to be played on all receivers, which will be available on the market in the future. We provide customers with a computer system that allows to innovatively record sound, but at the same time we are trying to be compatible with the commonly used solutions" - assured Dr. Żernicki.

PAP - Science and Scholarship in Poland, Karolina Olszewska

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