About us

The power of today's signal processing comes from the manipulation of the Fourier functions (exponential or sine/cosine). Similarly, the power of Digital Acoustics - acoustic field processing - is based on the manipulation of Fourier-Bessel functions. This new theory has led us to develop new technologies allowing to record, manipulate and reproduce acoustic fields.

Spatial Pick-up: recording acoustic fields

Actual technologies of "sound capture" consider separately the signals provided by each microphone used. Thanks to a radically innovating processing of these signals, the Spatial Pick-up technology makes it possible to optimally exploit all the available microphones in order to retranscribe all the collected information concerning a sound event. It is sufficient to know the spatial characteristics and position of each microphone in the sound space.

Thus, Spatial Pick-up technology brings an optimal answer to every application in function of the specifics constraints (cost, performances, size, simplicity...). Implementation of this technology led us to three prototypes of high spatial resolution microphone using, respectively, 5, 8 and 24 classic microphones. Fourier-Bessel functions allow one to record acoustic fields using any number of capsule of any type with any array organization (any position, any orientation). More detailed information is available in our scientific paper presented at the 114th AES convention in Amsterdam, A New Comprehensive Approach of Surround Sound Recording, preprint 5717.

The standard signal processing theory provides strong scientific basis for time sampling: a signal can be sampled in time without losses. Similarly, Trinnov Audio developed a generalized theoretical frame for spatial sampling. As a result, an acoustic field can be analyzed by any arrangement of any type of acoustic sensor organized at any position and orientation in space. The principle of generalized acoustic field sampling comes as follows:
If the acoustic field that stimulates the sensors is known, it's possible to determine the signals delivered by these sensors with a linear relation. This linear relation is expressed by a matrix called ?spatial sampling matrix? which provides the sensors signals from the Fourier-Bessel's coefficients of the acoustic field they have been exposed to. Now, the microphone principle is precisely the opposite: we know the signals provided by the sensors and we want to estimate the initial acoustic field. As a result, an acoustic field capture is performed by inverting the spatial sampling matrix using generalized inversion techniques.

Spatial Replay : acoustic fields restitution

Today's "multichannel" technologies consists in providing signals each dedicated to feed a single speaker, in order that the listener placed in the middle hear the desire effect. Spatial Replay technology gathers information describing an acoustic field and applies proprietary processing in order to determine the signals required for each speaker to optimally reproduce the acoustic field.

Thus, Spatial Replay technology gives an optimal answer to every application as a function of the specific constraints such as cost, performances, size, simplicity... The application of this technology has permitted Trinnov Audio to develop a prototype using from 2 to 16 speakers with random arrangement. As there is no restriction to optimally control tens or hundreds of loudspeakers, it gives strong basis for the future of audio technologies

An acoustic field reproduction system is composed of set of loudspeaker arbitrary arranged to surround the listening area. The scientific challenge consists in determining the loudspeaker feeds to optimally reproduce a given acoustic field represented by a set of Fourier-Bessel coefficients. The principle of acoustic field reproduction comes as follows:
If the loudspeaker feeds are known, it is possible to determine the acoustic field resulting from the contribution of all the loudspeaker with a linear relation. This linear relation is expressed by a matrix called ?loudspeaker radiation matrix? which provides the Fourier-Bessel coefficients of the acoustic field from the signals feeding the loudspeakers. Acoustic field reproduction problem is exactly the opposite: the acoustic field to reproduce is known while the loudspeaker feeds must be determined. As a result, an acoustic field reproduction is performed by inverting the loudspeaker radiation matrix using generalized inversion techniques.

Spatial Morphing : acoustic fields manipulation

The possibility to restitute accurately the acoustic field is not enough. Since music production is a creative process, there is a strong demand for specific tools to manipulate sound environment. Trinnov Audio developed a technology that directly process the acoustic field: Spatial Morphing. This technology opens to spatial audio the same transformation possibilities than the most advanced photo-editing software offers to pictures. As an example, in a full orchestra, a particular musician may be selected and attenuated or amplified, moved around, stretched or diffused in space.

Thus, Spatial Morphing technology brings an innovative solution for a variety of sound design needs. Trinnov Audio has developed prototype software to rotate the sound image, distort or emphasize the sound stage in a particular direction.

According to today?s signal processing technologies, it is often more efficient to manipulate the frequencial representation of a signal rather than to manipulate its temporal wave form. As an example filters are traditionally defined by their frequency response. The same concept applies to acoustic fields where it is more efficient to manipulate the Fourier-Bessel coefficients representation rather than it spatio-temporal wave form.
Any transformation of a linear acoustic field can be expressed as a specific recombination of its Fourier-Bessel coefficients. As a result, the Fourier-Bessel coefficients of the processed acoustic field are obtained by applying a transformation matrix on the Fourier-Bessel coefficients of the unprocessed acoustic field. This generic formulation of acoustic field processing opens infinite possibilities of manipulations. Different transformation categories can be defined, as an example:

- Spatial rotations: Rotate the entire acoustic field according to the standard 3 freedom degree of 3D rotations.
- Spatial distortions: Applies spatial transformation in the acoustic field, for instance the sound sources are moved according to an angular distortion law.
- Spatial convolution: Adjust the level of details in the acoustic field. As an example is can blur a focused recording or, in a certain extend, improve focusness a fussy recording.
- Spatial gating: makes it possible to select in space part of the entire acoustic field.