Bruce Wiggins

We report on on-going work investigating the feasibility of using tissue conduction to evince auditory spatial perception. Early results indicate that it is possible to coherently control externalization, range, directionality (including elevation), movement and some sense of spaciousness without presenting acoustic signals to the outer ear. Signal control techniques so far have utilised discrete signal feeds, stereo and 1st order ambisonic hierarchies. Some deficiencies in frontal externalization have been observed. We conclude that, whilst the putative components of the head related transfer function are absent, empirical tests indicate that coherent equivalents are perceptually utilisable. Some implications for perceptual theory and technological implementations are discussed along with potential practical applications and future lines of enquiry. 1.

Currently, the ITU standard surround sound speaker arrangement is based on an irregular 5 speaker array. However, this may change to an irregular 7 speaker array (as is now the standard on computer hardware) or more in the future. The Ambisonic system, pioneered by Micheal Gerzon, among others, in the late 1960’s, is very well suited to situations where the end system speaker configuration is not fixed in terms of number or position while also offering a simple way (via energy and velocity vector analysis) of quantifying the performance of such systems. However, while the derivation of the decoders is well documented for regular speaker arrangements [1], optimising the decoders for irregular layouts is not a simple task, where optimisation requires the solution of a set of non linear simultaneous equations, complicated further by the fact that multiple solutions are possible [2]. Craven [3] extended the system to use higher order circular harmonics and presented a 4 th order Ambison...

Ambisonics was developed in the 1970’s as a flexible, psycho-acoustically aware system. Developed at the same time as Quadraphonics, Ambisonics is an often mis-understood system that was far ahead of it’s time. Due to the ubiquity of surround sound equipment in modern computers and interest in live surround events becoming more widespread, is the time, finally, right for Ambisonics to come into its’ own?

The term sound spatialisation indicates a group of techniques for organizing and manipulating the spatial projection and movement of sound in a physical or virtual listening environment (Valiquet, 2011). In addition to pitch, timbre, intensity and duration, an understanding of space is a significant musical parameter and as such, spatial sound controllers should be regarded as instruments of musical expression (Pysievficz and Weinzierl, 2016); spatialiser design should therefore include immediacy, liveness, and learnability. Perez-Lopez (2015) identifies several design considerations for spatialisation systems, including: Is the performer exclusively controlling spatial parameters (in contrast to one who controls both spatialisation and sound generation)? What is the required level of expertise for expressivity and virtuosity? Is the spatial control made by an individual, or shared by a group of performers? Does the system provide a graphical user interface for real time visual feed...

Last year Google enabled spatial audio in head-tracked 360 videos using Ambisonics to binaural decoding on Android mobile devices. There was some early criticism of the 1st order to binaural conversion employed by Google, in terms of the quality of localisation and noticeable frequency response colouration. In this paper, the algorithm used by Google is discussed and the Ambisonics to Binaural conversion using virtual speakers analysed with respect to the resulting inter-aural time, level, and spectrum differences compared to an example HRTF data set. 1st to 35th order Ambisonics using multiple virtual speaker arrays are implemented and analysed with inverse filtering techniques for smoothing the frequency spectrum also discussed demonstrating 8th order decoding correctly reproducing binaural cues up to 4 kHz.

We report on on-going work investigating the feasibility of using tissue conduction to evince auditory spatial perception. Early results indicate that it is possible to coherently control externalization, range, directionality (including elevation), movement and some sense of spaciousness without presenting acoustic signals to the outer ear. Signal control techniques so far have utilised discrete signal feeds, stereo and 1st order ambisonic hierarchies. Some deficiencies in frontal externalization have been observed. We conclude that, whilst the putative components of the head related transfer function are absent, empirical tests indicate that coherent equivalents are perceptually utilisable. Some implications for perceptual theory and technological implementations are discussed along with potential practical applications and future lines of enquiry.

This thesis describes a system that can be used for the decoding of a three dimensional audio recording over headphones or two, or more, speakers. A literature review of psychoacoustics and a review (both historical and current) of surround sound systems is carried out. The need for a system which is platform independent is discussed, and the proposal for a system based on an amalgamation of Ambisonics, binaural and transaural reproduction schemes is given. In order for this system to function optimally, each of the three systems rely on providing the listener with the relevant psychoacoustic cues. The conversion from a five speaker ITU array to binaural decode is well documented but pair-wise panning algorithms will not produce the correct lateralisation parameters at the ears of a centrally seated listener. Although Ambisonics has been well researched, no one has, as yet, produced a psychoacoustically optimised decoder for the standard irregular five speaker array as specified by ...

Background Eliciting an auditory perception by means of mechanical transduction has been in use for hundreds of years. Several transmission pathways may be employed to deliver an audible experience, these pathways are often collectively referred to as bone conduction; as soft tissues and cerebrospinal fluid may feature significantly in these we refer to them as tissue conduction (TC). Four pathways out of several have been identified in numerous research studies as primary conduction pathways.

We describe experiments using multiple cranial transducers to achieve auditory spatial perceptual impressions via bone (BC) and tissue conduction (TC), bypassing the peripheral hearing apparatus. This could be useful in cases of peripheral hearing damage or where ear-occlusion is undesirable. Previous work (e.g. Stanley and Walker 2006, MacDonald and Letowski 2006) 1,2 indicated robust lateralization is feasible via tissue conduction. We have utilized discrete signals, stereo and first order ambisonics to investigate control of externalization, range, direction in azimuth and elevation, movement and spaciousness. Early results indicate robust and coherent effects. Current technological implementations are presented and potential development paths discussed.

This paper discusses a highly flexible and powerful implementation toolkit that allows new ideas in the field of multi-channel surround sound to be implemented with great ease and minimal development time. The key feature of the toolkit is that it enables complex surround sound encoding and decoding algorithms to be implemented in real-time with relative ease. Introduction The authors experience in designing and implementing encoding and decoding systems for multi-channel surround sound showed that although the design of such systems was not in itself excessively complex, the time consuming nature of designing circuit boards and software routines for each new system, often proved to be prohibitive. This was especially true if a quick test of a new idea or innovation was required. The availability of a rapid development and prototyping toolkit for the design and implementation of multi-channel surround sound processors soon became a clear requirement. This paper describes a highly fl...

Described in this paper is a method for the analysis and comparison of multi-speaker surround sound algorithms using HRTF data. Using Matlab and Simulink [1] a number of surround sound systems were modeled, both over multiple speakers (for listening tests) and using the MIT Media Labs HRTF set (for analysis)[2]. The systems under test were 1 Order Ambisonics over eight and five speakers, 2 Order Ambisonics over eight speakers and Amplitude panned 5.0 over five speakers. The listening test results were then compared to the HRTF analysis with favourable results.

In this paper, the development of a three dimensional Ambisonic reverb based on the open source Freeverb algorithm will be presented and discussed. This model is then extended to include processing in over-specified A-format, rather than B-format, variable scattering between channels along with controls for warping the distribution of the reflections to implement a reverb that is able to react to the source position in a spatially coherent way with an acoustical analysis of its performance. Introduction Ambisonics, as a spatial audio format, has been around since the 1970s, being pioneered by Michael Gerzon [1] as an improvement to the, then, state of the art system, Quadraphonics [2]. Work was carried out in the years that followed on music production techniques and equipment using Ambisonics, including the SoundField microphone which was able to the record four channels required for 1 order Ambisonic reproduction (for example see [3]). However, the tools needed to process and effe...

Capturing and replaying distance cues for multi-channel audio is currently an under-explored and under-exploited area. Panners that successfully give control of distance do not, currently, exist. However, recordings made with 1 order ambisonic, Soundfield, microphones replayed over an ambisonic rig can give realistic results with respect to distance perception (particularly when bringing sound sources inside the speaker array).

This paper discusses ambisonic sound design for a theatrical production of King Lear. Sound, and its use in theatre, has taken a back-seat in comparison to the development of other theatre technologies such as lighting, projection and automation in recent years. Spatial audio implementations in theatre give the sound designer and the artistic team much greater scope for creativity, along with improvements in source separation and intelligibility of sources due to spatial unmasking. A 360 degree video was also recorded, with first and third order ambisonic binaural reproductions of the sound design stitched on to the video to create a virtual reality experience. The project was successful, whilst highlighting some practical and perceptual limitations in spatial audio for theatre.

ABSTRACT We describe experiments using multiple cranial transducers to achieve auditory spatial perceptual impressions via bone (BC) and tissue conduction (TC), bypassing the peripheral hearing apparatus. This could be useful in cases of peripheral hearing damage or where ear-occlusion is undesirable. Previous work (e.g. Stanley and Walker 2006, MacDonald and Letowski 2006) indicated robust lateralization is feasible via tissue conduction. We have utilized discrete signals, stereo and first order ambisonics to investigate control of externalization, range, direction in azimuth and elevation, movement and spaciousness. Early results indicate robust and coherent effects. Current technological implementations are presented and potential development paths discussed.

We describe experiments using multiple cranial transducers to achieve auditory spatial perceptual impressions via bone (BC) and tissue conduction (TC), bypassing the peripheral hearing apparatus. This could be useful in cases of peripheral hearing damage or where ear-occlusion is undesirable. Previous work (e.g. Stanley and Walker 2006, MacDonald and Letowski 2006) indicated robust lateralization is feasible via tissue conduction. We have utilized discrete signals, stereo and first order ambisonics to investigate control of externalization, range, direction in azimuth and elevation, movement and spaciousness. Early results indicate robust and coherent effects. Current technological implementations are presented and potential development paths discussed.

The reduction of spatial variation in the quality of reproduced sound within a defined space using varied loudspeaker placements is a significant challenge for sound engineers. Dr Bruce Wiggins has conducted research into encoding, decoding and processing algorithms using Ambisonics, a system based around full-sphere sound reproduction. The outcomes of the research have been made accessible to the wider community by the creation of a suite of software plug-ins (WigWare), a production workflow, and associated teaching materials which can enable commercial audio workstations to benefit from Ambisonics. There are numerous recorded instances of successful use. The significance and reach of this work are articulated and evidenced in this article produced for the Research Excellence Framework (REF) 2014 (http://www.ref.ac.uk/).

ABSTRACT Over the years, quad-rotor helicopters have generated considerable interest in the community of Intelligent Control. This can be linked to the fact that they are simple in construction and very agile. Control of the vehicle is achieved by varying the lift forces of the four rotors, which depend on the flow conditions around the propellers and the propeller speeds. In this paper, computations performed with an analytical model of the quad-rotor built in Matlab/Simulink are compared with those obtained using CFD (Computational Fluid Dynamics) on a 3-D Solidworks model of the same helicopter. The two are also compared with results from real experiments, with a general agreement between the numerical and experimental results, which can be judged satisfactory. This is enough to validate the use of the simulation results for similar future analysis and prediction of the helicopter movements and effects of wind flow on it.

Eliciting an auditory perception by means of mechanical transduction bypassing the peripheral hearing apparatus has been recorded as early as the 16 th century. Excluding its audiometric use to assess ear pathology, bone and soft tissue conduction has received very little interest until the last two decades. Previous work during this time (Stanley and Walker 2006, MacDonald and Letowski 2006) has indicated robust lateralisation is feasible via mechanical transduction. This paper reports on an extension to this work, adding the front-back and up-down axes. Background Eliciting an auditory perception by means of mechanical transduction has been in use for hundreds of years. Several transmission pathways may be employed to deliver an audible experience, these pathways are often collectively referred to as bone conduction; as soft tissues and cerebrospinal fluid may feature significantly in these we refer to them as tissue conduction (TC). Four pathways out of several have been identifi...

This presentation covers the basic design of the WigWare AmbiFreeverb 2 3D reverberation VST plug-in for Mac and PC. This was followed by a demonstration on a 20 speaker with-height rig at the University of Derby's Sounds in Space research symposium event. To download the plug-in, visit http://www.brucewiggins.co.uk/

The reduction of spatial variation in the quality of reproduced sound within a defined space using varied loudspeaker placements is a significant challenge for sound engineers. Dr Bruce Wiggins has conducted research into encoding, decoding and processing algorithms using Ambisonics, a system based around full-sphere sound reproduction. The outcomes of the research have been made accessible to the wider community by the creation of a suite of software plug-ins (WigWare), a production workflow, and associated teaching materials which can enable commercial audio workstations to benefit from Ambisonics. There are numerous recorded instances of successful use.

Capturing and replaying distance cues for multi-channel audio is currently an under-explored and under-exploited area.  Panners that successfully give control of distance do not, currently exist.  However, recordings made with 1st order ambisonic, Soundfield microphones replayed over an ambisonic rig can give realistic results with respect to distance perception (particularly when bringing sound sources inside the speaker array). 

Near-field effect, resulting from the wave front curvature of near-field sources, is one cue recorded by the microphone, but not reproduced by software or hardware panners.  Papers by Daniel (2003, 2004) discuss the encoding and decoding of ambisonic material with particular reference to higher-order ambisonics, and describe ‘near-field coding’ filters which encode near-field effect while pre-compensating for finite loudspeaker reproduction distance.  While existing research concentrates on its simulation, this report documents an investigation into near-field effect in Soundfield ST350 and MK V tetrahedral microphones.  It is found that, as a result of calibration for a flat frequency response at a practical source distance, the Soundfield microphone responses bear strong similarity to various near-field coding filters, suggesting the existence of an optimum loudspeaker array radius for positional localisation.  On determination of this distance, recordings may be adapted for proper reproduction at any chosen reference distance using the WigWare ambisonic plug-ins created at the University of Derby.

Ambisonics was developed in the 1970’s as a flexible, psycho-acoustically aware system1.  Developed at the same time as Quadraphonics2, Ambisonics is an often mis-understood system that was far ahead of it’s time.  Due to the ubiquity of surround sound equipment in modern computers and interest in live surround events becoming more widespread, is the time, finally, right for Ambisonics to come into its’ own?

In this paper, the definition of what makes a system Ambisonic is clarified with reference made to the traditional energy and velocity vector theory, higher order systems and use in both the live and domestic environment.  More recent developments by the author are discussed with respect to irregular Ambisonic decoder design (such as for the ITU 5.1 speaker array) and analysis using Head Related Transfer Function data showing the extra insight this can give into the performance of one, seemingly similar, decoder design over another.  The freely available suite of VST plug-ins (comprising of decoders, panners and an Ambisonic reverb) created using this technology are also presented, with case studies of their use in student projects at the University of Derby.

This thesis describes a system that can be used for the decoding of a three dimensional audio recording over headphones or two, or more, speakers.  A literature review of psychoacoustics and a review (both historical and current) of surround sound systems is carried out.  The need for a system which is platform independent is discussed, and the proposal for a system based on an amalgamation of Ambisonics, binaural and transaural reproduction schemes is given.  In order for this system to function optimally, each of the three systems rely on providing the listener with the relevant psychoacoustic cues.  The conversion from a five speaker ITU array to binaural decode is well documented but pair-wise panning algorithms will not produce the correct lateralisation parameters at the ears of a centrally seated listener.  Although Ambisonics has been well researched, no one has, as yet, produced a psychoacoustically optimised decoder for the standard irregular five speaker array as specified by the ITU as the original theory, as proposed by Gerzon and Barton (1992) was produced (known as a Vienna decoder), and example solutions given, before the standard had been decided on.  In this work, the original work by Gerzon and Barton (1992) is analysed, and shown to be suboptimal, showing a high/low frequency decoder mismatch due to the method of solving the set of non-linear simultaneous equations. A method, based on the Tabu search algorithm, is applied to the Vienna decoder problem and is shown to provide superior results to those shown by Gerzon and Barton (1992) and is capable of producing multiple solutions to the Vienna decoder problem.  During the write up of this report Craven (2003) has shown how 4th order circular harmonics (as used in Ambisonics) can be used to create a frequency independent panning law for the five speaker ITU array, and this report also shows how the Tabu search algorithm can be used to optimise these decoders further.  A new method is then demonstrated using the Tabu search algorithm coupled with lateralisation parameters extracted from a binaural simulation of the Ambisonic system to be optimised (as these are the parameters that the Vienna system is approximating).  This method can then be altered to take into account head rotations directly which have been shown as an important psychoacoustic parameter in the localisation of a sound source (Spikofski et al., 2001) and is also shown to be useful in differentiating between decoders optimised using the Tabu search form of the Vienna optimisations as no objective measure had been suggested.  Optimisations for both Binaural and Transaural reproductions are then discussed so as to maximise the performance of generic HRTF data (i.e. not individualised) using inverse filtering methods, and a technique is shown that minimises the amount of frequency dependant regularisation needed when calculating cross-talk cancellation filters.

Currently, the ITU standard surround sound speaker arrangement is based on an irregular 5 speaker array.  However, this may change to an irregular 7 speaker array (as is now the standard on computer hardware) or more in the future.  The Ambisonic system, pioneered by Micheal Gerzon, among others, in the late 1960’s, is very well suited to situations where the end system speaker configuration is not fixed in terms of number or position while also offering a simple way (via energy and velocity vector analysis) of quantifying the performance of such systems.  However, while the derivation of the decoders is well documented for regular speaker arrangements [1], optimising the decoders for irregular layouts is not a simple task, where optimisation requires the solution of a set of non linear simultaneous equations, complicated further by the fact that multiple solutions are possible [2].  Craven [3] extended the system to use higher order circular harmonics and presented a 4th order Ambisonic decoder (9 input channels), although the derivation method used was not presented. 

In this paper a semi-automated decoder optimisation system using heuristic methods will be presented that will be shown to be robust enough to generate higher order Ambisonic decoders based on the energy and velocity vector parameters.  This method is then analytically compared to Craven’s decoder using both energy/velocity vector and head related transfer function based methods.


[1] Gerzon, M.A. (1985) Ambisonics in Multichannel Broadcasting and Video.  Journal of the Audio Engineering Society, Vol. 33, No. 11, p. 851-871.
[2] Gerzon, M. A. & Barton, G. J. (1992) Ambisonic Decoders for HDTV.  Proceedings of the 92nd International AES Convention, Vienna. 24 – 27 March. Preprint 3345.
[3] Craven, P. (2003), Continuous Surround Panning for 5-speaker Reproduction, AES 24th International Conference, Banff, Canada.