foundations
the research and the software bambi builds on
the inspiration
Institute of Electronic Music and Acoustics (IEM), Graz — Daniel Rudrich, lead developer
free and open source, GPLv3
The open reference for higher-order ambisonics in a DAW: how a plugin suite for the whole sphere can work, from encoding to visualising a sound field. bambi was written from the published theory rather than from its code, and would not exist in this form without it.
ambisonics
Jérôme Daniel
doctoral thesis, Université Paris 6, 2000
Higher-order ambisonics, and the max-rE weighting bambi reads and places fields with.
Franz Zotter and Matthias Frank
Springer, 2019, open access
The reference for the spherical harmonics, rotations and decoding under everything bambi does.
Christian Nachbar, Franz Zotter, Etienne Deleflie and Alois Sontacchi
ambiX — A Suggested Ambisonics Format
Ambisonics Symposium, Lexington, 2011
The channel order and normalisation bambi speaks: ACN, SN3D.
warping the sound field
Hannes Pomberger and Franz Zotter
Warping of 3D Ambisonic Recordings
Ambisonics Symposium, Lexington, 2011
The warp that pulls a sound field towards one pole of an axis.
rooms and reverberation
Jont B. Allen and David A. Berkley
Image method for efficiently simulating small-room acoustics
Journal of the Acoustical Society of America 65(4), 1979
The early reflections: a room's walls as mirror images of the source.
Carl F. Eyring
Reverberation time in “dead” rooms
Journal of the Acoustical Society of America 1(2), 1930
How long a room of a given size and absorption rings.
Jean-Marc Jot and Antoine Chaigne
Digital delay networks for designing artificial reverberators
AES 90th Convention, Paris, 1991, preprint 3030
The feedback delay network the tail is built on, and how to give it a decay per band.
Sebastian J. Schlecht and Emanuël A. P. Habets
Feedback Delay Networks: Echo Density and Mixing Time
IEEE/ACM Transactions on Audio, Speech, and Language Processing 25(2), 2017
How dense a delay network’s echoes grow, and when.
Alexander Lindau, Linda Kosanke and Stefan Weinzierl
Journal of the Audio Engineering Society 60(11), 2012
When the reflections stop being heard one by one, and the tail takes over.
Julius O. Smith III
Physical Audio Signal Processing
online book, CCRMA, Stanford
Delay-network reverberation in practice: mode density and tonal correction.
Geraint Luff, Signalsmith Audio
article, 2021
A clear, practical path from diffusion to a working tail.
decoding to loudspeakers
International Telecommunication Union
Recommendation ITU-R BS.2051: Advanced sound system for programme production
ITU-R
The ten loudspeaker layouts built into the decoder, by name and in the recommendation’s channel order.
Franz Zotter and Matthias Frank
All-Round Ambisonic Panning and Decoding
Journal of the Audio Engineering Society 60(10), 2012
AllRAD: a loudspeaker decoder designed from the loudspeakers’ positions alone, with the weighting the decoder calls audience.
Franz Zotter, Stefan Riedel and Matthias Frank
All-Round Ambisonic Decoding: Spread and Correlation
DAGA, Stuttgart, 2022
What mixing imaginary loudspeakers back into their neighbours costs, and why the decoder drops them instead.
binaural rendering
Christian Schörkhuber, Markus Zaunschirm and Robert Höldrich
Binaural Rendering of Ambisonic Signals via Magnitude Least Squares
DAGA, Munich, 2018
MagLS: above the frequency where the order can still hold the phase, the decoder fits the magnitudes alone.
Markus Zaunschirm, Christian Schörkhuber and Robert Höldrich
Journal of the Acoustical Society of America 143(6), 2018
The diffuse-field constraint the decoder’s binaural decode keeps: a diffuse sound field reaches the ears with the head’s own spectra and coherence between the ears.
heads
Lorenz Häusler
Data-Driven HRTF Individualization: Towards Enhanced Elevation Perception Using Interactive User Optimization
master’s thesis, University of Music and Performing Arts Graz, 2024
Where the decoder’s head model starts: a head split into what all heads share and what is one listener’s, two sliders for the listener’s part, and finding them by ear against a real loudspeaker.
Fabian Brinkmann et al.
Journal of the Audio Engineering Society 67(9), 2019
HUTUBS, one of the two databases the decoder’s learned head comes from.
Rahulram Sridhar, Joseph G. Tylka and Edgar Choueiri
A Database of Head-Related Transfer Functions and Morphological Measurements
AES 143rd Convention, New York, 2017
The 3D3A database, the other one.
Cal Armstrong, Lewis Thresh, Damian Murphy and Gavin Kearney
Applied Sciences 8(11), 2018
The Neumann KU100 as SADIE II measured it, the decoder’s second head.
Audio Engineering Society
AES69: Spatial acoustic data file format (SOFA)
AES standard
The file a measured head, or a whole decoder as filters, arrives in.
Sebastian A. Ausili et al.
Sound Localization with Hearables in Transparency Mode
Audiology Research 15(3), 2025
Why personalising a head is done on open headphones: an earbud’s transparency mode shifts the level difference between the ears and loses the spectral cues.
head tracking
Daniel Rudrich
AirPods orientation to OSC, macOS, MIT licence
The frame the AirPods report in, and the look-and-nod calibration that replaces it when a pair sits askew.
Leo McCormack and Archontis Politis
AES Conference on Immersive and Interactive Audio, York, 2019
The orientation messages over OSC the decoder’s tracker reads, and the layout files it shares with the IEM suite.
layouts, filters and files
Fons Adriaensen
free software
AmbDec’s decoder configuration, read as a layout, and jconvolver’s filter sets, which a loudspeaker array’s maker ships, converted to the SOFA filters the decoder plays.
Christian Hoene et al.
free software, BSD licence
How the decoder reads a SOFA file.