Angelo Farina
Dipartimento di Ingegneria e Architettura, Università di Parma, HTTP://www.angelofarina.it - mail: angelo.farina@unipr.it
AIDA srl, Spinoff company of the University of Parma HTTP://www.aidasrl.it
Capturing and reproducing
spatial audio
Topics
(not necessarily in order)
1. Brief history of spatial sound recording and reproduction 2. "Discrete" multichannel systems: spaced microphone
arrays (A-B recordings), source localization based on time- delay
3. "Coincident" multichannel systems: compact microphone arrays (M-S, X-Y recording), source localization based on amplitude
4. The Ambisonics method: classical and modern implementations
5. "virtual microphones"
6. SPS (Spatial PCM Sampling), a new approach for
capturing, processing and reproducing a complete 3D sound field
Who is where ?
“They are here”
“You are there”
“They are here”
Gmebaphone
(1973)“You are there”
URBAN SOUNDS
Collaboration between “Industrial Engineering Department - University of Parma” and “Casa
della Musica”
GOALS:
- delivering to posterity an archive of recorded sound fields to document Parma in 2012 with advanced 3D surround recording techniques
- creation of a “musical”
Ambisonics composition for leading the audience through a virtual tour of the town
RECORDING EQUIPMENT
EIGENMIKETM by mhAcoustics
Array with 32 ½” capsules of good quality, frequency response up to 20 kHz
Preamplifiers and A/D converters inside the sphere, with ethernet interface
Recorder: Mac Book Pro 13”
Software: Plogue Bidule
Gain controller: custom Python controller
THE PLACES
A first set of 30 places:
Airport and Train Station
Two public parks
Several squares
A bridge
An highway
An outdoor market
Indoor public places as:
Swimming pool
Underground parking
School canteen
Italian Opera Theater
Commercial Center
A panoramic photo was taken in the same position of the microphone, by means of a Sony Bloggie panoramic-mirror camera
THE VIRTUAL TOUR OF PARMA
PROCESSING OF THE RECORDINGS
The processing technique was developed by the RAI Research Center in Turin and by AIDA, a spinoff of the University of Parma.
We don’t assume any theory for computing the filters: they are derived directly from a set of measurements.
m = 1…M microphones
d = 1…D directions
δ(t) δ(t)
A matrix of measured impulse response coefficients is formed and the matrix has to be numerically inverted
16 virtual microphones
=
3rd Order Ambisonics
Directivity patterns of the 16 virtual microphones
The patterns correspond to spherical harmonics of
orders 0, 1, 2 and 3:
X-Volver VST plugin in Plogue Bidule host
Realtime convolution of the 32 microphone signals with the matrix of 32x16 FIR filters
32x16 FIR Matrix:
• 2048 samples
• 48kHz – 24bit
THE MIX
Performed in a threated room equipped with:
Desktop PC
RME Hammerfall audio interface
Apogee AD-16x digital-to-analog converter
N.2 QSC CX168 amplifiers
N.16 Turbosound Impact 50
MIXING SOFTWARE:
Linux Ubuntu OS
Ardour
AMB-Plugins, AMBDEC and Zita-Rev by Fons Adriaensen
The listener is leaded through a well-defined route, starting from
the train station and ending to the airport of the town.
The composition is accompanied by a “musical” soundscape, created with Bloom by Brian Eno and spatializated in Ambisonic using the software by Fons Adriaensen.
Bloom
Intercative/generative iPad application.
iPad with Bloom
Recording and
Ambisonic spatialization
THE LISTENING ROOM
Wave Field Synthesis room, named “Sala Bianca”, in “Casa del Suono” museum.
Dimensions: 7.5 x 4.5 x 4.5 meters Number of speakers: 189
Control Software: designed by Fons Adriaensen
The Wave Field System is used for simulating eight “virtual” speakers placed on a regular octagon at a distance of 15 meters from the centre of the room.
Low-cost hardware for WFS
The cheaper solution is based on a Mac Pro connected with an RME MADIface XT, three RME ADI-648 connected with a rack of ADAT converters (Aphex, each driving an 8-
channels amplifier (QSC)
THE LISTENING ROOM
Virtual Sources Mixer
WFS Realtime Monitoring
WFS system VU Meters
CONCLUSIONS
The goal of the “Urban Sounds” project was dual:
• the creation of an archive of 3D urban soundscapes recorded in Parma
• the realization of an immersive virtual tour of the town performed in a WFS room
The composition, object of this paper, is actually available in “Casa del Suono” museum and the soundscapes archive is at disposal of artists and listeners.
• the number of the sampled places should be increased, covering other significant locations in Parma, in order to create a vast archive of urban soundscapes;
• the 3D recordings could be accompanied with a panoramic video, not only with a panoramic photo, for a complete immersive experience;
• the 3D recordings could be performed with different microphone probes, such as the 32 capsules cylindrical array actually in development at University of Parma;
• a permanent installation could be placed in the museum, giving to the visitors the choice of the town places in which they would like to be surrounded (the idea is a map of the town on a tablet that is used as a remote control).
FUTURE DEVELOPMENTS
• Eigenmike 32 (with EMIB Interface)
• Metric Halo MIO 2882
• 4 B&K 4189 microphones
• Soundfield ST 250
• Macbook Pro 17 “ (4 TB SSD, FW-800)
• 8 Gopro Session cameras
Sound Recording system #1
• Cylindircal Array 32 (with EMIB Interface)
• Macbook Pro 13 “ (1 TB SSD, FW-800)
• Word Clock connection with Sound Syestem #1
• Nikon Kemission 360 camera
• Samsung Gear 360 camera
Sound Recording system #2
• DPA-4 Microphone
• Neumann KU-100 Dummy Head
• 2 Neumann Cardioids K140 in ORTF configuration
• Zoom F8 recorder
• LG 360 Cam
