In my previous article (link) we have made an overview of active acoustic improvement systems, in more detail we have seen how it is possible to improve the acoustics of a small or large room.
This type of system generally employs one of the following two approaches:
- "Regenerative approach”Uses acoustic feedback, reproducing the sound picked up by the microphones through the speakers and then picking up that sound influenced by the room acoustics, thus creating an acoustic“ loop ”that amplifies the acoustic energy of the room.
- "Online approach”Uses convolution signal processing to add a variety of synthesized reflected sound data (measured impulse responses) to the sound collected via the microphones, to create the desired sound environment.
In this article, we focus on Yamaha's implementation of such acoustic enhancement systems.
AFC Enhance
AFC Enhance is the name given by Yamaha to its version of the AFC system, now in its fourth generation.
To implement its system, Yamaha used a “hybrid” approach that uses both methods seen in the previous paragraph.
Through a detailed check of the reverb and early reflections, the sound that propagates throughout the room can be adjusted as needed while maintaining the natural acoustic properties of the room structure.
So AFC Enhance does not introduce artificial reverbs, instead it exploits the natural properties of the environment while keeping the sounds of musical instruments and voices unaltered.
In practice, the control of the acoustics of the environment takes place through the use of several microphones and speakers located in the space of the environment to be improved.
System
At the heart of the system is an audio engine that works on 48/96 KHz, equipped with 128 channels audio via card DANTE.
AFC supports 32 input microphones, 4 line inputs, 24 auxiliary audio inputs and 96 outputs.
The whole system can be controlled (remote control and monitoring) by ProVisionaire Control (Windows), ProVisionaire Touch (iPad) or MCP1 (wall control).
FIR filters
All the magic of AFC happens in the audio engine which uses much more powerful FIR filters than previous versions, providing a very natural sound with highly detailed reflections even for spaces that have little natural reverb.
Let's talk about up to 10.6 seconds at 48 kHz e 5.3 sec at 96 kHz.
Integration
In support of AFC, Yamaha has partnered with other companies. To date, the system can be integrated with Steinberger Nuendo products and with NEXO.
New
Nuendo is one of the most advanced audio production solutions available and is a great choice for those working in the film, television, game audio, and immersive audio industries.
A Nuendo-based system can consist of a simple laptop and Dante cardfor a total of 64 objects that can be integrated with the AFC Image application, up to a complete studio environment with a maximum of 128 objects and the Nuage touch control surface.
Nuendo offers a mix of channel-based and object-based tracks with dynamic automation. Nuendo's VST Multipanner can control the positioning of the audio object with AFC Image and this can be done manually or through an interactive live control. Interactive live control from mixing consoles, stage tracking systems or OSC applications is possible. Calling up live overview sequences can be done via markers or by synchronizing with timecode.
Nexo NS-1
NEXO's NS-1 software features an intuitive drag and drop interface and provides a simulation of audio coverage and immersion in three dimensions.
The NS-1 workflow is fast and intuitive.
First we draw the space on which we are going to work. This can also be done by importing files from EASE, Google Earth, 3D Sketchup, collection, STL, JPG o PDF.
Then the audience spaces and the speakers are added and in an interactive way it is possible to check the result of the project.
AFC Image - immersive audio
AFC Image allows you to check the position of the audio perceived by the audience.
Technically AFC Image is a software application that runs in parallel with the AFC Enhance application.
Normally using the classic stereo configuration, the audio varies according to the position of the listener, with AFC Image this position in the "image audio" it can be moved and placed anywhere independently from the listening position.
Let's talk about "Sources" or Audio "objects" (Object based audio) instead of the more classic concept of audio channel, which is still supported by AFC.
Below I list the main features of AFC Image.
Audio object or “Object based” audio
With the concept of object-based audio, you can make an audio source coincide with the position of real objects.
Controlling audio objects can be done in several ways: RIVAGE PM, CL and consoles digital mixers of QL series by Yamaha, Stagetrackers, third party products and tablet (via browser).
In particular, the Stagetracker system, developed by the Norwegian company TTA, is a product that works with radiofrequency (RF) sensors and tags, even of such tiny dimensions that they can be “worn” by the performers.
Stagetracker allows you to follow up to one hundred artists at the same time on stage by tracking the sensors in real time in space, which will then be positioned in the sound field.
Its use is not limited to audio but also extends to video and lighting.
Render Area
You can convert the audio pan to any geometric configuration. From a cube to a 16-sided polygon in which audio “objects” can be placed.
In addition, there are three levels with their respective heights that can be individually adjusted.
Speaker Zoning
With Speaker zoning it is possible to assign audio objects to one or more speakers of the system.
In all, up to 32 zones can be defined.
Object & Channels
Object-based audio is extremely versatile, while in some situations it is more practical to work with audio channels, AFC Image allows you to use audio channels and objects at the same time.
Up to 128 objects are possible, third-party immersive systems are also supported.
3D Reverbs
In a real acoustic space, the perceived reverb varies depending on the position of the listener.
With proprietary technology, the result of decades of experience, Yamaha has created reverbs optimized for the positions of individual objects, creating a much deeper and more realistic effect. The direction and spread of the reverb can be freely controlled from an intuitive graphical interface.
Binaural Output
Immersive sound can also be experienced in headset, AFC Image provides the necessary tools for binaural listening. Immersive content can be heard in a two-channel audio form to be monitored and streamed to remote locations.
Conclusions
AFC Enhance was created to improve the acoustics of rooms, whether they are meeting and conference rooms or concert halls.
In cases where the acoustics do not facilitate the sound at all (or even limit the performance), AFC Enhance can be used to enhance or transform the natural features of the room.
All the AFC technology (which includes many patents filed over the years) allows you to modify the environmental reverberation while leaving the voices and musical instruments unaltered.
Finally, its installation, which includes microphones and speakers, allows you to act on the room without expensive construction work and to add versatility of uses to the hall.
