Dr Russell Mason
Senior Lecturer (IoSR), Tonmeister Programme Director
Qualifications: BMus(Tonmeister), PhD (Surrey)
Email: r.mason@surrey.ac.uk
Phone: Work: 01483 68 6535
Room no: 08A BC 03
Further information
Biography
Dr Russell Mason is a Senior Lecturer in the Institute of Sound Recording (IoSR) at the University of Surrey. He is Programme Director for the Tonmeister programme, teaches Audio Engineering to students in all years of this programme, and conducts research into aspects of perception and measurement of audio.
Russell graduated from the Tonmeister Music and Sound Recording degree course at Surrey in 1998, and was offered the opportunity to continue his studies with a PhD jointly in the IoSR and the Department of Psychology, and sponsored by BBC Research and Development. This project, in collaboration with Bang & Olufsen, Genelec and Nokia among others, examined the perception of spatial impression detail, including creating new methods for synthesising spatial sound and a binaural hearing model capable of predicting the perceived effect. Following his PhD, Russell gained funding from the Engineering and Physical Sciences Research Council (EPSRC) to continue the work, which resulted in an advanced binaural hearing model that can successfully predict the perceived width and location of sound sources in the horizontal plane, and the perceived width of acoustical environments.
In 2004, Russell gained a lectureship in the IoSR, and in 2009 was promoted to Senior Lecturer. During this time, Russell has taught a wide range of modules, including Electronics Practicals, Audio Laboratory, Audio Research Seminars, Computer Audio Systems, Technical Projects, and Audio Engineering 1, 2 & 3. He has also taught Master's level Speech and Audio Processing for the Department of Electronic Engineering.
Russell has also undertaken a number of critical administrative roles for the Tonmeister programme. This includes serving as Admissions Tutor for 7 years, during which he revised the admission procedure, including the creation of an online interview booking system and the creation of new entrance tests. He is currently Programme Director for the Tonmeister programme, which includes responsibility for the direction of the programme, managing changes and updates to the programme, managing the IoSR budgets, overseeing upgrades and management of facilities, and mentoring junior staff.
Russell has continued his research into psychoacoustic engineering; specifically the perception and measurement of audio. This research involved the development of novel subjective testing methods and stimulus synthesis techniques, as well as developing new computational algorithms to mimic human auditory perception and furthering understanding of the human auditory system. Recent projects have investigated the role of head movement in spatial perception, optimal design of microphone arrays for localisation around the horizontal plane, computational auditory scene analysis based on psychoacoustic cues, and perception and modelling of spectral magnitude distortions. He is currently working on further development of measurement techniques of spatial attributes of sound, such as integration of results across frequency and perception of elevation cues. He is also applying the techniques he has developed to the fields of auditory masking and modelling of quality in the presence of interfering signals.
So far, Russell has been involved in funding bids that have brought nearly £900,000 to Surrey (approximately half of this has been as principal investigator) from a range of sources including EPSRC and industry. This has included collaboration with a wide range of industrial partners such as Bang & Olufsen, Adrian James Acoustics, Harman-Becker Automotive, Wolfson Microelectronics, and BBC Research and Development.
Outside the University, Russell is an active member of the Audio Engineering Society. He was a member of the committee of the British section for many years including the creation of the section website. He has also contributed towards the organisation of a number of British section conferences, and many International conferences in the UK and abroad. He acted as papers co-chair for the Audio Metadata conference and has chaired many paper sessions and given invited presentations to conferences in Japan, Australia, France, Germany and the USA.
Russell also has a strong musical background, having performed music from the age of 4 and studying trumpet, piano and music theory for many years in both jazz and classical styles. In his spare time, Russell is an active musician, playing trumpet in the department Trad Band and in the department Big Band that he co-founded as a final year undergraduate. He also appreciates a good curry.
Research Collaborations
Current research projects:
- Perceptually optimised sound zones
- Perception of loudspeaker directivity
- Perception and measurement of auditory elevation cues
- Adaptation of spatial audio quality measures to the automotive environment
Past research projects:
- The role of head movement in the analysis of spatial impression - Funded by EPSRC (EP/D049253/1)
- Automated separation of sound sources in reverberant environments using spatial cues - Funded by EPSRC (EP/P503892/1)
- Perceptual sound field reconstruction and coherent emulation - Funded by EPSRC (EP/E064507/1)
- Perceptually motivated measurement of spatial sound attributes for audio-based information systems - Funded by EPSRC (GR/R55528/01)
- Eureka 1653 Multichannel enhancement of domestic user stereo applications (MEDUSA) - in collaboration with Bang & Olufsen, Genelec, Nokia and the University of Lulea-Pitea
Publications
Journal articles
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(2011) 'Ideal Binary Mask Ratio: a novel metric for assessing binary-mask-based sound source separation algorithms'. IEEE IEEE Transactions on Audio, Speech and Language Processing, 19 (7), pp. 2039-2045.Full text is available at: http://epubs.surrey.ac.uk/7195/
Abstract
A number of metrics has been proposed in the literature to assess sound source separation algorithms. The addition of convolutional distortion raises further questions about the assessment of source separation algorithms in reverberant conditions as reverberation is shown to undermine the optimality of the ideal binary mask (IBM) in terms of signal-to-noise ratio (SNR). Furthermore, with a range of mixture parameters common across numerous acoustic conditions, SNR–based metrics demonstrate an inconsistency that can only be attributed to the convolutional distortion. This suggests the necessity for an alternate metric in the presence of convolutional distortion, such as reverberation. Consequently, a novel metric—dubbed the IBM ratio (IBMR)—is proposed for assessing source separation algorithms that aim to calculate the IBM. The metric is robust to many of the effects of convolutional distortion on the output of the system and may provide a more representative insight into the performance of a given algorithm.
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(2011) 'Head-movement-aware signal capture for evaluation of spatial acoustics'. Multi Science Publishing Building Acoustics, 18 (1), pp. 207-226.Full text is available at: http://epubs.surrey.ac.uk/712909/
Abstract
This research incorporates the nature of head movement made in listening activities, into the development of a quasi- binaural acoustical measurement technique for the evaluation of spatial impression. A listening test was conducted where head movements were tracked whilst the subjects rated the perceived source width, envelopment, source direction and timbre of a number of stimuli. It was found that the extent of head movements was larger when evaluating source width and envelopment than when evaluating source direction and timbre. It was also found that the locus of ear positions corresponding to these head movements formed a bounded sloped path, higher towards the rear and lower towards the front. This led to the concept of a signal capture device comprising a torso-mounted sphere with multiple microphones. A prototype was constructed and used to measure three binaural parameters related to perceived spatial impression - interaural time and level differences (ITD and ILD) and interaural cross- correlation coefficient (IACC). Comparison of the prototype measurements to those made with a rotating Head and Torso Simulator (HATS) showed that the prototype could be perceptually accurate for the prediction of source direction using ITD and ILD, and for the prediction of perceived spatial impression using IACC. Further investigation into parameter derivation and interpolation methods indicated that 21 pairs of discretely spaced microphones were sufficient to measure the three binaural parameters across the sloped range of ear positions identified in the listening test.
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(2010) 'Dynamic precedence effect modeling for source separation in reverberant environments'. IEEE Transactions on Audio, Speech and Language Processing, 18 (7), pp. 1867-1871.Full text is available at: http://epubs.surrey.ac.uk/2935/
Abstract
Reverberation continues to present a major problem for sound source separation algorithms. However, humans demonstrate a remarkable robustness to reverberation and many psychophysical and perceptual mechanisms are well documented. The precedence effect is one of these mechanisms; it aids our ability to localize sounds in reverberation. Despite this, relatively little work has been done on incorporating the precedence effect into automated source separation. Furthermore, no work has been carried out on adapting a precedence model to the acoustic conditions under test and it is unclear whether such adaptation, analogous to the perceptual Clifton effect, is even necessary. Hence, this study tests a previously proposed binaural separation/precedence model in real rooms with a range of reverberant conditions. The precedence model inhibitory time constant and inhibitory gain are varied in each room in order to establish the necessity for adaptation to the acoustic conditions. The paper concludes that adaptation is necessary and can yield significant gains in separation performance. Furthermore, it is shown that the initial time delay gap and the direct-to-reverberant ratio are important factors when considering this adaptation. © 2010 IEEE.
- . (2006) 'Musically Representative Signals for Use in Interaural Cross-Correlation Coefficient Measurements'. Acta Acustica United with Acustica, 92 (5), pp. 787-796.
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(2005) 'Frequency dependency of the relationship between perceived auditory source width and the interaural cross-correlation coefficient for time-invariant stimuli.'. Acoustical Society of America Journal of the Acoustical Society of America, United States: 117 (3 Pt 1), pp. 1337-1350.doi: 10.1121/1.1853113
- . (2005) 'The effect of various source signal properties on measurements of the interaural cross-correlation coefficient'. Acoustical Society of Japan Acoustical Science and Technology, 26 (2), pp. 102-113.
- . (2001) 'Verbal and non-verbal elicitation techniques in the subjective assessment of spatial sound reproduction'. Audio Engineering Society Journal of the Audio Engineering Society, 49 (5), pp. 366-384.
Conference papers
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(2012) 'Determining the threshold of acceptability for an interfering audio programme'. Audio Engineering Society Preprint Audio Engineering Society Preprint, Budapest, Hungary: 132nd Audio Engineering Society Convention 8639Full text is available at: http://epubs.surrey.ac.uk/728336/
Abstract
An experiment was performed in order to establish the threshold of acceptability for an interfering audio programme on a target audio programme, varying the following physical parameters: target programme, interferer programme, interferer location, interferer spectrum, and road noise level. Factors were varied in three levels in a Box-Behnken fractional factorial design. The experiment was performed in three scenarios: information gathering, entertainment, and reading/working. Nine listeners performed a method of adjustment task to determine the threshold values. Produced thresholds were similar in the information and entertainment scenarios, however there were significant differences between subjects, and factor levels also had a significant effect: interferer programme was the most important factor across the three scenarios, whilst interferer location was the least important.
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(2011) 'Prediction of perceived elevation using multiple psuedo-binaural microphones'. London, UK : Audio Engineering Society Audio Engineering Society Preprint, London, UK: 130th Audio Engineering Society ConventionFull text is available at: http://epubs.surrey.ac.uk/712910/
Abstract
Computational auditory models that predict the perceived location of sound sources in terms of azimuth are already available, yet little has been done to predict perceived elevation. Interaural time and level differences, the primary cues in horizontal localisation, do not resolve source elevation, resulting in the ‘Cone of Confusion’. In natural listening, listeners can make head movements to resolve such confusion. To mimic the dynamic cues provided by head movements, a multiple microphone sphere was created, and a hearing model was developed to predict source elevation from the signals captured by the sphere. The prototype sphere and hearing model proved effective in both horizontal and vertical localisation. The next stage of this research will be to rigorously test a more physiologically accurate capture device.
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(2011) 'Spaciousness rating of 8-channel stereophony-based microphone arrays'. London, UK : Audio Engineering Society Preprint, London, UK: 130th Audio Engineering Society Convention 8340Full text is available at: http://epubs.surrey.ac.uk/2929/
Abstract
In previous studies, the localisation accuracy and the spatial impression of 3-2 stereo microphone arrays were discussed. These showed that 3-2 stereo cannot produce stable images to the side and to the rear of the listener. An octagon loudspeaker array was therefore proposed. Microphone array design for this loudspeaker configuration was studied in terms of localisation accuracy, locatedness and sound image width. This paper describes an experiment conducted to evaluate the spaciousness of 10 different microphone arrays used in different acoustical environments. Spaciousness was analyzed as a function of sound signal, acoustical environment and microphone array’s characteristics. It showed that the height of the microphone array and the original acoustical environment are the two variables that have the most influence on the perceived spaciousness, but that microphone directivity and the position of sound sources is also important.
- . (2010) 'Verification of microphone techniques for a novel surround sound system'. Marseille, France : Marseille, France: Laboratory of Mechanics and Acoustics, Centre National de la Recherche Scientifique
- . (2010) 'Development of a novel surround sound format and associated microphone techniques'. King’s College, London :
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(2010) 'A comparison of computational precedence models for source separation in reverberant environments'. Audio Engineering Society Audio Engineering Society Preprint, London, UK: 128th Audio Engineering Society Convention 7981Full text is available at: http://epubs.surrey.ac.uk/2936/
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(2010) 'Time and level localisation curves for a regularly-spaced octagon loudspeaker array'. London, UK : Audio Engineering Society Audio Engineering Society Preprint, London, UK: 128th Audio Engineering Society Convention 8079Full text is available at: http://epubs.surrey.ac.uk/2937/
Abstract
Multichannel microphone array designs often use the localisation curves that have been derived for 2-0 stereophony. Previous studies showed that side and rear perception of phantom image locations require somewhat different curves. This paper describes an experiment conducted to determine localisation curves using an octagonal loudspeaker setup. Various signals with a range of interchannel time and level differences were produced between pairs of adjacent loudspeakers, and subjects were asked to evaluate the perceived sound event’s direction and its locatedness. The results showed that the curves for the side pairs of adjacent loudspeakers are significantly different to the front and rear pairs. The resulting curves can be used to derive suitable microphone techniques for this loudspeaker setup.
- . (2010) 'Investigation into and modelling of head movement for objective evaluation of the spatial impression of audio'. Boston, USA : Acoustical Society of America Journal of the Acoustical Society of America, Baltimore, USA: 159th Meeting of the Acoustical Society of America 127, pp. 1886-1886.
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(2010) 'A quasi-binaural approach to head-movement-aware evaluation of spatial acoustics'. Sidney : The International Congress on Acoustics (ICA) Proceedings of the International Symposium on Room Acoustics, Melbourne, Australia: International Symposium on Room Acoustics. A Satellite of the International Congress on Acoustics. General papers 4 (1), pp. 292-300.Full text is available at: http://epubs.surrey.ac.uk/712914/
Abstract
This research incorporates the nature of head movement made in listening activities, into the development of a quasibinaural acoustical measurement technique for the evaluation of spatial impression. A listening test was conducted where head movements were tracked whilst the subjects rated the perceived source width, envelopment, source direction and timbre of a number of stimuli. It was found that the extent of head movements was larger when evaluating source width and envelopment than when evaluating source direction and timbre. It was also found that the locus of ear positions corresponding to these head movements formed a bounded sloped path, higher towards the rear and lower towards the front. This led to the concept of a signal capture device comprising a torso-mounted sphere with multiple microphones. A prototype was constructed and used to measure three binaural parameters related to perceived spatial impression - interaural time and level differences (ITD and ILD) and interaural crosscorrelation coefficient (IACC). Comparison of the prototype measurements to those made with a rotating Head and Torso Simulator (HATS) showed that the prototype could be perceptually accurate for the prediction of source direction using ITD and ILD, and for the prediction of perceived spatial impression using IACC. Further investigation into parameter derivation and interpolation methods indicated that 21 pairs of discretely spaced microphones were sufficient to measure the three binaural parameters across the sloped range of ear positions identified in the listening test.
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(2010) 'Development of a head-movement-aware signal capture system for the prediction of acoustical spatial impression'. Sidney : International Congress of Acoustics (ICA) Proceedings of the 20th International Congress on Acoustics, Sydney, Australia: 20th International Congress on Acoustics 4, pp. 2768-2775.Full text is available at: http://epubs.surrey.ac.uk/712915/
Abstract
This research introduces a novel technique for capturing binaural signals for objective evaluation of spatial impression; the technique allows for simulation of the head movement that is typical in a range of listening activities. A subjective listening test showed that the amount of head movement made was larger when listeners were rating perceived source width and envelopment than when rating source direction and timbre, and that the locus of ear positions corresponding to the pattern of head movement formed a bounded sloped path – higher towards the rear and lower towards the front. Based on these findings, a signal capture system was designed comprising a sphere with multiple microphones, mounted on a torso. Evaluation of its performance showed that a perceptual model incorporating this capture system is capable of perceptually accurate prediction of source direction based on interaural time and level differences (ITD and ILD), and of spatial impression based on interaural cross-correlation coefficient (IACC). Investigation into appropriate parameter derivation and interpolation techniques determined that 21 pairs of spaced microphones were sufficient to measure ITD, ILD and IACC across the sloped range of ear positions.
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(2010) 'Validation of a simple spherical head model as a signal capture device for head-movement-aware prediction of perceived spatial impression'. Audio Engineering Society Proceedings of the 40th International AES Conference, Tokyo, Japan: AES 40th International Conference (Spatial Audio: Sense the Sound of Space)Full text is available at: http://epubs.surrey.ac.uk/712913/
Abstract
In order to take head movement into account in objective evaluation of perceived spatial impression (including source direction), a suitable binaural capture device is required. A signal capture system was suggested that consisted of a head-sized sphere containing multiple pairs of microphones which, in comparison to a rotating head and torso simulator (HATS), has the potential for improved measurement speed and the capability to measure time varying systems, albeit at the expense of some accuracy. The error introduced by using a relatively simple sphere compared to a more physically accurate HATS was evaluated in terms of three binaural parameters related to perceived spatial impression – interaural time and level differences (ITD and ILD) and interaural cross-correlation coefficient (IACC). It was found that whilst the error in the IACC measurements was perceptually negligible when the sphere was mounted on a torso, the differences in measured ITD and ILD values between the sphere-with-torso and HATS were not perceptually negligible. However, it was found that the sphere-with-torso could give accurate predictions of source location based on ITD and ILD, through the use of a look-up table created from known ITD-ILD-direction mappings. Therefore the validity of the multi-microphone sphere-with-torso as a binaural signal capture device for perceptually relevant measurements of source direction (based on ITD and ILD) and spatial impression (based on IACC) was demonstrated.
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(2009) 'Localisation curves for a regularly-spaced octagon loudspeaker array'. New York, USA : Audio Engineering Society Audio Engineering Society Preprint, New York, USA: 127th Audio Engineering Society Convention 7915Full text is available at: http://epubs.surrey.ac.uk/2938/
Abstract
Multichannel microphone array designs often use the localisation curves that have been derived for 2-0 stereophony. Previous studies showed that side and rear perception of phantom image locations require somewhat different curves. This paper describes an experiment conducted to evaluate localisation curves using an octagonal loudspeaker setup. Interchannel level differences were produced between the loudspeaker pairs forming each of the segments of the loudspeaker array, one at a time, and subjects were asked to evaluate the perceived sound event’s direction and its locatedness. The results showed that the localisation curves derived for 2-0 stereophony are not directly applicable, and that different localisation curves are required for each loudspeaker pair.
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(2009) 'Perception of head-position-dependent variations in interaural cross-correlation coefficient'. Munich, Germany : Audio Engineering Society Audio Engineering Society Preprint, Munich, Germany: 126th Audio Engineering Society Convention 7729Full text is available at: http://epubs.surrey.ac.uk/2939/
Abstract
Experiments were undertaken to elicit the perceived effects of head-position-dependent variations in the interaural cross-correlation coefficient of a range of signals. A graphical elicitation experiment showed that the variations in the IACC strongly affected the perceived width and depth of the reverberant environment, as well as the perceived width and distance of the sound source. A verbal experiment gave similar results, and also indicated that the head-position-dependent IACC variations caused changes in the perceived spaciousness and envelopment of the stimuli.
- . (2009) 'The role of head movement in the analysis of spatial impression'. Institute of Hearing Research: European Career Workshop for PhD Students in Hearing Research
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(2009) 'The role of head movement in the analysis of spatial impression'. Engineering and Physical Sciences Research Council London, UK: EPSRC People in Systems Theme DayFull text is available at: http://epubs.surrey.ac.uk/2952/
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(2008) 'Taking head movements into account in measurement of spatial attributes'. Institute of Acoustics Proceedings of the Institute of Acoustics Reproduced Sound Conference, Brighton, UK: Institute of Acoustics 24th Reproduced Sound Conference 30 (6), pp. 239-246.Full text is available at: http://epubs.surrey.ac.uk/2950/
Abstract
Measurements of the spatial attributes of auditory environments or sound reproduction systems commonly only consider a single receiver position. However, it is known that humans make use of head movement to help to make sense of auditory scenes, especially when the physical cues are ambiguous. Results are summarised from a three-year research project which aims to develop a practical binaural-based measurement system that takes head movements into account. Firstly, the head movements made by listeners in various situations were investigated, which showed that a wide range of head movements are made when evaluating source width and envelopment, and minimal head movements made when evaluating timbre. Secondly, the effect of using a simplified sphere model containing two microphones instead of a head and torso simulator was evaluated, and methods were derived to minimise the errors in measured cues for spatial perception that were caused by the simplification of the model. Finally, the results of the two earlier stages were combined to create a multi-microphone sphere that can be used to measure spatial attributes incorporating head movements in a perceptually-relevant manner, and which allows practical and rapid measurements to be made.
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(2008) 'Initial investigation of signal capture techniques for objective measurement of spatial impression considering head movement'. Audio Engineering Society Preprint Audio Engineering Society Preprint, Amsterdam, The Netherlands: 124th Audio Engineering Society Convention 7331Full text is available at: http://epubs.surrey.ac.uk/712917/
Abstract
In a previous study it was discovered that listeners normally make head movements attempting to evaluate source width and envelopment as well as source location. To accommodate this finding in the development of an objective measurement model for spatial impression, two capturing models were introduced and designed in this research, based on binaural technique: 1) rotating Head And Torso Simulator (HATS), and 2) a sphere with multiple microphones. As an initial study, measurements of interaural time difference (ITD), level difference (ILD) and cross-correlation coefficient (IACC) made with the HATS were compared with those made with a sphere containing two microphones. The magnitude of the differences was judged in a perceptually relevant manner by comparing them with the just-noticeable differences (JNDs) of these parameters. The results showed that the differences were generally not negligible, implying the necessity of enhancement of the sphere model, possibly by introducing equivalents of the pinnae or torso. An exception was the case of IACC, where the reference of JND specification affected the perceptual significance of its difference between the two models.
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(2008) 'Improvements to a Spherical Binaural Capture Model for Objective Measurement of Spatial Impression with Consideration of Head Movements'. San Francisco, USA : Audio Engineering Society Audio Engineering Society Preprint, San Francisco, USA: 125th Audio Engineering Society Convention 7579Full text is available at: http://epubs.surrey.ac.uk/712911/
Abstract
This research aims, ultimately, to develop a system for the objective evaluation of spatial impression, incorporating the finding from a previous study that head movements are naturally made in its subjective evaluation. A spherical binaural capture model, comprising a head-sized sphere with multiple attached microphones, has been proposed. Research already conducted found significant differences in interaural time and level differences, and cross-correlation coefficient, between this spherical model and a head and torso simulator. It is attempted to lessen these differences by adding to the sphere a torso and simplified pinnae. Further analysis of the head movements made by listeners in a range of listening situations determines the range of head positions that needs to be taken into account. Analyses of these results inform the optimum positioning of the microphones around the sphere model.
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(2007) 'Perceptually modelled effects of interchannel crosstalk in multichannel microphone technique'. New York, USA : Audio Engineering Society Audio Engineering Society Convention 123, New York, USA: 123rd Audio Engineering Society Conference 7200Full text is available at: http://epubs.surrey.ac.uk/2941/
Abstract
One of the most noticeable perceptual effects of interchannel crosstalk in multichannel microphone technique is an increase in perceived source width. The relationship between the perceived source-width-increasing effect and its physical causes was analysed using an IACC-based objective measurement model. A description of the measurement model is presented and the measured data obtained from stimuli created with crosstalk and those without crosstalk are analysed visually. In particular, frequency and envelope dependencies of the measured results and their relationship with the perceptual effect are discussed. The relationship between the delay time of the crosstalk signal and the effect of different frequency content on the perceived source width is also discussed in this paper.
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(2007) 'Perception and detection of auditory offsets with single simple musical stimuli in a reverberant environment'. Proceedings of the AES International Conference, Full text is available at: http://epubs.surrey.ac.uk/7051/
Abstract
It is apparent that little research has been undertaken into the perception and automated detection of auditory offsets compared to auditory onsets. A study was undertaken which took a perceptually motivated approach to the detection of auditory offsets. Firstly, a subjective experiment was completed that investigated the effect of: the sound source temporal properties; the presence or absence of reverberation; the direct to reverberant level; and the presence or absence of binaural cues on the perceived auditory offset time. It was found in this case that: the sound source temporal properties had a small effect; the presence of reverberation caused the perceived auditory offset to be later in most cases; the direct to reverberant ratio had no significant effect; and the binaural cues had no significant effect on the perceived offset times. Measurements were conducted which showed that the -30dB threshold below the peak level of the slowest decaying frequency bands could be used as a reasonable predictor of the subjective results.
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(2007) 'An investigation into head movements made when evaluating various attributes of sound'. Vienna, Austria : Audio Engineering Society Audio Engineering Society Preprint, Vienna, Austria: 122nd Audio Engineering Society Convention 7031Full text is available at: http://epubs.surrey.ac.uk/2942/
Abstract
This research extends the study of head movements during listening by including various listening tasks where the listeners evaluate spatial impression and timbre, in addition to the more common task of judging source location. Subjective tests were conducted in which the listeners were allowed to move their heads freely whilst listening to various types of sound and asked to evaluate source location, apparent source width, envelopment, and timbre. The head movements were recorded with a head tracker attached to the listener’s head. From the recorded data, the maximum range of movement, mean position and speed, and maximum speed were calculated along each axis of translational and rotational movement. The effects of various independent variables, such as the attribute being evaluated, the stimulus type, the number of repetition, and the simulated source location were examined through statistical analysis. The results showed that whilst there were differences between the head movements of individual subjects, across all listeners the range of movement was greatest when evaluating source width and envelopment, less when localising sources, and least when judging timbre. In addition, the range and speed of head movement was reduced for transient signals compared to longer musical or speech phrases. Finally, in most cases for the judgement of spatial attributes, head movement was in the direction of source direction.
- . (2006) 'Implementation and application of a binaural hearing model to the objective evaluation of spatial impression'. Pitea, Sweden : Sound: 28th Audio Engineering Society Internation Conference, pp. 331-342.
- . (2005) 'PCA-based down-mixing, Workshop on 5.1 Downmix in Practice'. New York, USA : Audio Engineering Society New York, USA: 119th Audio Engineering Society Convention
- . (2005) 'PCA-based down-mixing'. New York: Workshop on 5.1 Downmix in Practice, 119th Audio Engineering Society Convention
- . (2005) 'Preference-based testing and reference-based testing'. New York: Workshop on Automotive Sound Systems Part II: Considerations in Methodology and Sound Quality Attributes for Subjective Evaluations, 119th Audio Engineering Society Convention
- . (2005) 'Preference-based testing and reference-based testing, Workshop on Automotive Sound Systems Part II: Considerations in Methodology and Sound Quality Attributes for Subjective Evaluations'. New York, USA : Audio Engineering Society New York, USA: 119th Audio Engineering Society Convention
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(2004) 'Spatial impression: measurement and perception of concert hall acoustics and reproduced sound'. Hyogo, Japan : Proceedings of the International Symposium on Room Acoustics, Hyogo, Japan: International Symposium on Room Acoustics: Design and ScienceFull text is available at: http://epubs.surrey.ac.uk/7050/
Abstract
Auditory width measurements based on the interaural cross-correlation coefficient (IACC) are often used in the field of concert hall acoustics. However, there are a number of problems with such measurements, including large variations around the centre of a room and a limited range of values at low frequencies. This paper explores how some of these problems can be solved by applying the IACC in a more perceptually valid manner and using it as part of a more complete hearing model. It is proposed that measurements based on the IACC may match the perceived width of stimuli more accurately if a source signal is measured rather than an impulse response, and when factors such as frequency and loudness are taken into account. Further developments are considered, including methods to integrate the results calculated in different frequency bands, and the temporal response of spatial perception
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(2004) 'Development of the interaural cross-correlation coefficient into a more complete auditory width prediction model'. Kyoto, Japan : International Congress on Acoustics Proceedings of the 18th International Congress on Acoustics, Kyoto, Japan: 18th International Congress on Acoustics IV, pp. 2453-2456.Full text is available at: http://epubs.surrey.ac.uk/2944/
Abstract
Auditory width measurements based on the interaural cross-correlation coefficient (IACC) are often used in the field of concert hall acoustics. However, there are a number of problems with such measurements, including large variations around the centre of a room and a limited range of values at low frequencies. This paper explores how some of these problems can be solved by applying the IACC in a more perceptually valid manner and using it as part of a more complete hearing model. It is proposed that measurements based on the IACC may match the perceived width of stimuli more accurately if a source signal is measured rather than an impulse response, and when factors such as frequency and loudness are taken into account. Further developments are considered, including methods to integrate the results calculated in different frequency bands, and the temporal response of spatial perception
- . (2004) 'Integration of measurements of interaural cross-correlation coefficient and interaural time difference within a single model of perceived source width'. San Francisco, USA : Audio Engineering Society Preprint, San Francisco: 117th Audio Engineering Society Convention 6137
- . (2004) 'Evaluation of an auditory source width prediction model based on the interaural cross-correlation coefficient'. San Diego, California : Journal of the Acoustical Society of America, Sound: 148th meeting of the Acoustical Society of America 116
- . (2004) 'Perceptually Motivated Measurement and Control of Digital Music'. York : Sound: The Future of Audio: Digital Music in 2010 (DMRN Conference)
- . (2004) 'Perception, measurement and synthesis of spatial impression'. London : Sound: Audio Engineering Society British Section Lecture
- . (2003) 'Creation and verification of a controlled experimental stimulus for investigating selected perceived spatial attributes'. Amsterdam : Audio Engineering Society Preprint, Amsterdam: 114th Audio Engineering Society Convention 5771
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(2002) 'The perceptual relevance of extant techniques for the objective measurement of spatial impression'. London : Proceedings of the Institute of Acoustics, London: Auditorium Acoustics 2002 Conference 24Full text is available at: http://epubs.surrey.ac.uk/7055/
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(2002) 'A comparison of objective measurements for predicting selected subjective spatial attributes'. Audio Engineering Society Audio Engineering Society Preprint, Munich, Germany: 112th Audio Engineering Society Convention 5591Full text is available at: http://epubs.surrey.ac.uk/2954/
Abstract
A controlled subjective experiment was undertaken to evaluate the relative merits of objective measurement techniques for predicting selected perceived spatial attributes of reproduced sound. The stimuli consisted of a number of anechoic recordings of single sound sources that were reproduced in a simulated concert hall and captured using a number of simulated multichannel microphone techniques. These were reproduced in a listening room and the subjects were asked to judge the perceived source width and perceived environment width of each stimulus. A number of objective measurements were made at the listening position and these were then compared with the subjective judgements. The results showed that a perceptually-grouped measurement of the experimental stimuli using a technique based on the interaural cross-correlation coefficient matched the subjective judgements most accurately, though the difference between this measurement and a number of other types was small.
- . (2001) 'Physical measures related to spatial attributes, Workshop on Evaluation of Spatial Sound Reproduction'. Amsterdam, The Netherlands : Audio Engineering Society Amsterdam, Netherlands: 110th Audio Engineering Society Convention
- . (2001) 'Interaural time difference fluctuations: their measurement, subjective perceptual effect and application in sound reproduction.'. Schloss Elmau Germany : Proceedings of the 19th International Audio Engineering Society Conference, Elmau, Germany: 19th International Audio Engineering Society Conference, pp. 252-271.
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(2001) 'An investigation of interaural time difference fluctuations, part 2: dependence of the subjective effect on audio frequency.'. Amsterdam : Audio Engineering Society Preprint, Amsterdam: 110th Audio Engineering Society Convention 5389Full text is available at: http://epubs.surrey.ac.uk/7057/
Abstract
The effect of the audio frequency of narrow-band noise signals with a sinusoidal ITD fluctuation was investigated. To examine this, a subjective experiment was carried out using a match to sample method and stimuli delivered over headphones. It was found that the magnitude of the subjective effect is dependent on audio frequency and that the relationship between the audio frequency and a constant subjective effect appears to be based on equal maximum phase difference fluctuations.
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(2001) 'An investigation of interaural time difference fluctuations, part 3: the subjective effect of fluctuations in continuous stimuli delivered over loudspeakers'. Audio Engineering Society Preprint, New York, USA: 111th Audio Engineering Society Convention 5457Full text is available at: http://epubs.surrey.ac.uk/7059/
Abstract
The subjective spatial effect of continuous noise signals with interaural time difference fluctuations was investigated. These fluctuations were created by sinusoidal interchannel time difference fluctuations between signals that were presented over loudspeakers. Both verbal and non-verbal elicitation techniques were applied to examine the subjective effect. It was found that the predominant effect of increasing the fluctuation magnitude was an increase in the apparent width of the perceived sound source.
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(2001) 'An investigation of interaural time difference fluctuations, part 4: the subjective effect of fluctuations in decaying stimuli delivered over loudspeakers'. Audio Engineering Society Preprint, New York: 111th Audio Engineering Society Convention 5458Full text is available at: http://epubs.surrey.ac.uk/7058/
Abstract
The subjective spatial effect of decaying noise signals with interaural time difference fluctuations was investigated. These fluctuations were created by sinusoidal interchannel time difference fluctuations between signals which were presented over loudspeakers. Both verbal and non-verbal elicitation techniques were applied to examine the subjective effect. It was found that the predominant effect of increasing the fluctuation magnitude was an increase in the apparent width of the acoustical environment whilst the apparent size of the perceived sound source did not change.
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(2001) 'An investigation of interaural time difference fluctuations, part 1: the subjective spatial effect of fluctuations delivered over headphones.'. Audio Engineering Society Audio Engineering Society Preprint, Amsterdam, Netherlands: 110th Audio Engineering Society Convention 5383Full text is available at: http://epubs.surrey.ac.uk/2956/
Abstract
The subjective spatial effect of noise signals with sinusoidal ITD fluctuations was investigated. Both verbal and non-verbal elicitation experiments were carried out to examine the subjective effect of the ITD fluctuations with a number of fluctuation frequencies and fluctuation magnitudes. It was found that the predominant effect of increasing the fluctuation magnitude was an increase in the perceived width of the sound.
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(2000) 'An assessment of spatial performance of virtual home theatre algorithms by subjective and objective methods'. Audio Engineering Society Audio Engineering Society Preprint, Paris, France: 108th Audio Engineering Society Convention 5137Full text is available at: http://epubs.surrey.ac.uk/2955/
Abstract
A controlled subjective test was carried out to assess selected spatial qualities of three virtual home theatre processors. The subjective results were used to evaluate a number of objective measurements based on the interaural cross-correlation coefficient (IACC). A novel implementation of the IACC was found which appears to correlate well with the subjective data.
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(2000) 'Verbal and non-verbal elicitation techniques in the subjective assessment of spatial sound reproduction'. Audio Engineering Society Preprint, Los Angeles, USA: 109th Audio Engineering Society Convention 5225Full text is available at: http://epubs.surrey.ac.uk/7060/
Abstract
Current research into spatial audio has shown an increasing interest in the way subjective attributes of reproduced sound are elicited from listeners. The emphasis at present is on verbal semantics, however studies suggest that non-verbal methods of elicitation could be beneficial. Research into the relative merits of these methods has found that non-verbal responses may result in different elicited attributes compared to verbal techniques. Non-verbal responses may be closer to the perception of the stimuli than the verbal interpretation of this perception. There is evidence that drawing is not as accurate as other non-verbal methods of elicitation when it comes to reporting the localisation of auditory images. However, the advantage of drawing is its ability to describe the whole auditory space rather than a single dimension.
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(1999) 'Microphone techniques for multichannel surround sound'. London, UK : Audio Engineering Society Proceedings of the 1999 AES UK conference, Audio: the second century, London, UK: Audio Engineering Society UK Conference, Audio: the second century, pp. 15-24.Full text is available at: http://epubs.surrey.ac.uk/2947/
Abstract
A controlled subjective test was carried out to assess selected qualities of three microphone techniques for capturing the ambient sound of a concert hall surround sound. The effects of signal delay between the front and rear channels and microphone distance were explored. The tests indicate that the perceived results are programme-dependent, but that a compromise can be found using delayed close microphones, giving similar quality for the range of programme items used.
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(1999) 'An investigation of microphone techniques for ambient sound in surround sound systems'. Munich, Germany : Audio Engineering Society Audio Engineering Society Preprint, Munich, Germany: 106th Audio Engineering Society Convention 4912Full text is available at: http://epubs.surrey.ac.uk/2946/
Abstract
A controlled subjective test was carried out to assess selected qualities of three ambient microphone techniques for surround sound The effects of signal delay and microphone distance were explored. The tests indicate that the perceived results are programme dependent, but that a compromise can be found using delayed close microphones, giving similar quality for the range of programme items used.
Posters
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(2010) A perceptually–inspired approach to machine sound source separation in real rooms. University of Surrey Postgraduate Research ConferenceFull text is available at: http://epubs.surrey.ac.uk/7250/
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(2010) Development of a novel surround sound format and associated microphone techniques. University of Surrey Postgraduate Research ConferenceFull text is available at: http://epubs.surrey.ac.uk/2931/
Abstract
The most common surround sound format (often known as 5.1) does not enable accurate positioning of sounds to the side or the rear. Based on a detailed analysis of the binaural hearing cues used by humans, a new surround sound loudspeaker format has been developed using 8 loudspeakers arranged in a regular octagon. Listening tests have been conducted to demonstrate the superiority of this setup compared to 5.1 in terms of accurate sound positioning around a listener. In order to enable development of microphone techniques to capture soundfields for this reproduction system, localisation curves needed to be derived that map the relationship between a range of interchannel time and levels differences of signals (ICTDs and ICLDs respectively) and the perceived sound location. Various signals with a range of ICLDs and ICTDs were produced between pairs of adjacent loudspeakers, and listeners were asked to evaluate the perceived sound's direction and its locatedness. The results showed that the curves for the side pairs of adjacent loudspeakers are significantly different to the front and rear pairs. The resulting curves have been used to derive suitable microphone techniques for this loudspeaker setup.
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(2010) A system for the auralisation of synthetic sound scenes using headphones and head-tracking. University of Surrey Postgraduate Research ConferenceFull text is available at: http://epubs.surrey.ac.uk/726082/
Abstract
Auralisation is the process of rendering virtual sound fields. It is used in areas including: acoustic design, defence, gaming and audio research. As part of a PhD project concerned with the influence of loudspeaker directivity on the perception of reproduced sound, a fully-computed auralisation system has been developed. For this, acoustic modelling software is used to synthesise and extract binaural impulse responses of virtual rooms. The resulting audio is played over headphones and allows listeners to experience the excerpt being reproduced within the synthesised environment. The main advance with this system is that impulse responses are calculated for a number of head positions, which allows the listeners to move when listening to the recreated sounds. This allows for a much more realistic simulation, and makes it especially useful for conducting subjective experiments on sound reproduction systems and/or acoustical environments which are either not available or are even impractical to create. Hence, it greatly increases the range and type of experiments that can be undertaken at Surrey. The main components of the system are described, together with the results from a validation experiment which demonstrate that this system provides similar results to experiments conducted previously using loudspeakers in an anechoic chamber.
Theses and dissertations
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(2002) Elicitation and measurement of auditory spatial attributes in reproduced sound. Full text is available at: http://epubs.surrey.ac.uk/7056/
Abstract
This thesis has investigated objective measurements that relate to the perceived spatial attributes of reproduced sound. Research has been conducted into extant measurements that aim to quantify the perceived spatial attributes of concert hall acoustics, and those that are most likely to be successful for measuring the properties of reproduced sound have been identified. A relatively new measurement technique that may relate to the spatial perception of reproduced sound has also been analysed. This measurement is based on the quantification of the magnitude of fluctuations in interaural time and level difference. This has been investigated in detail, and the subjective effect that this measurement relates to has been elicited in a number of subjective experiments. The experiments used various types of noise stimuli that contained a range of fluctuations in interaural time difference. It was found that when the fluctuations are contained within a part of the signal that is perceived to be a sound source, a variation in the magnitude of the fluctuations alters the perceived width of that source. When the fluctuations are contained within a part of the signal that is perceived to be reverberation, a variation in the magnitude of the fluctuations alters the perceived width of the acoustical environment. This research has been applied to the development of novel objective measurement techniques, and to the specification of the subjective attributes that relate to these techniques. A final evaluation experiment has found that listeners can relate to the attribute descriptors that have been elicited, and that the novel objective measurement techniques that have been developed match the subjective data at least as well as the extant measurement techniques.
PhD Thesis
Mason, R. 2002: 'Elicitation and measurement of auditory spatial attributes in reproduced sound', PhD thesis, University of Surrey.
Teaching
Current teaching responsibilities:
- Audio Engineering 1
- Audio Engineering 2
- Audio Engineering 3
- Technical Projects
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