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Dr Tim Brookes

Senior Lecturer in Audio (IoSR)

Qualifications: BSc, MSc, DPhil (York), MAES

Email:
Phone: Work: 01483 68 6539
Room no: 06 BC 03

Further information

Biography

Dr Tim Brookes joined the University as Lecturer in Audio in January 1997, having previously been a Research Associate in the Department of Electronics at the University of York. Prior to that he worked in Nottingham at Business Systems Computing and at The Square Centre recording studios.

He is Director of Research in the IoSR, Senior Professional Training Tutor for the Tonmeister Programme, and Webmaster for the IoSR.

Research Interests

Tim's research activities are on the engineering side of psychoacoustics: measuring, modelling and exploiting the relationships between the physical characteristics of sound and the corresponding perception evoked in listeners.

Postgraduate & funded projects supervised & managed include:

Publications

Journal articles

  • Brookes TS, Mason RD. (2013) 'Auditory source width of paired vs single narrow-band signals in terms of centre-frequency, loudness level and interaural cross-correlation coefficient'. Acoustical Society of America Journal of the Acoustical Society of America,
    [ Status: Submitted ]
  • Hummersone C, Mason R, Brookes T. (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.
    doi: 10.1109/TASL.2011.2109380
    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.

  • Kim C, Mason RD, Brookes T. (2011) 'Head-movement-aware signal capture for evaluation of spatial acoustics'. Multi Science Publishing Building Acoustics, 18 (1), pp. 207-226.
    doi: 10.1260/1351-010X.18.1-2.207
    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.

  • Hummersone C, Mason R, Brookes T. (2010) 'Dynamic precedence effect modeling for source separation in reverberant environments'. IEEE Transactions on Audio, Speech and Language Processing, 18 (7), pp. 1867-1871.
    doi: 10.1109/TASL.2010.2051354
    Full text is available at: http://epubs.surrey.ac.uk/2935/
  • Neher T, Brookes T, Rumsey F. (2006) 'A Hybrid Technique for Validating Unidimensionality of Perceptual Variation in a Spatial Auditory Stimulus Set'. Journal of the Audio Engineering Society, 54 (4), pp. 259-275.
  • Supper B, Brookes T, Rumsey F. (2006) 'An auditory onset detection algorithm for improved automatic source localization'. IEEE Transactions on Audio, Speech and Language Processing, 14 (3), pp. 1008-1017.
  • Neher T, Brookes T, Mason R. (2006) 'Musically Representative Signals for Use in Interaural Cross-Correlation Coefficient Measurements'. Acta Acustica United with Acustica, 92 (5), pp. 787-796.
  • Mason R, Brookes T, Rumsey F. (2005) 'Frequency dependency of the relationship between perceived auditory source width and the interaural cross-correlation coefficient for time-invariant stimuli.'. J Acoust Soc Am, United States: 117 (3 Pt 1), pp. 1337-1350.
  • Mason R, Brookes T, Rumsey F. (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.
  • Brookes T, Tyrrell A, Howard D. (2000) 'On the differences between conventional and auditory spectrograms of English consonants'. Logopedics Phoniatrics Vocology, 25 (2), pp. 72-79.
  • Tyrrell AM, Howard DM, Brookes T. (1998) 'Transputer-based human hearing simulation'. Simulation Practice and Theory, 6 (5), pp. 479-491.
    doi: 10.1016/S0928-4869(97)00036-0
  • Howard DM, Hirson A, Brookes TS, Tyrrell AM. (1995) 'Spectrography of Disputed Speech Samples by Peripheral Human Hearing Modelling'. Forensic Linguistics, 2 (1), pp. 22-38.

Conference papers

  • Ashby T, Mason R, Brookes T. (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 Convention
    Full 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.

  • Brookes TS, williams . (2010) 'Testing a prototype timbre morpher'. London: DMRN+4: Digital Music Research Network One-day Workshop
  • Brookes TS. (2010) 'Psychoacoustic Engineering at the Institute of Sound Recording'. London, UK: Audio Engineering Society British Section 'Cutting Edge Research' Lecture Series
  • Hummersone C, Mason R, Brookes TS. (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 7981
    Full text is available at: http://epubs.surrey.ac.uk/2936/
  • Kim C, Mason R, Brookes T. (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.
  • Kim C, Mason R, Brookes TS. (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.

  • Brookes TS, Williams D. (2010) 'Perceptually-Motivated Audio Morphing: Warmth'. Audio Engineering Society Convention Proceedings, Paper 8019, London, UK: AES 128th Convention
    Full text is available at: http://epubs.surrey.ac.uk/712912/

    Abstract

    A system for morphing the warmth of a sound independently from its other timbral attributes was coded, building on previous work morphing brightness only (1), and morphing brightness and softness (2). The new warmth-softness-brightness morpher was perceptually validated using a series of listening tests. A Multidimensional Scaling analysis of listener responses to paired-comparisons showed perceptually orthogonal movement in two dimensions within a warmth-morphed and everything-else-morphed stimulus set. A verbal elicitation experiment showed that listeners’ descriptive labeling of these dimensions was as intended. A further ‘quality control’ experiment provided evidence that no ‘hidden’ timbral attributes were altered in parallel with the intended ones. A complete timbre morpher can now be considered for further work, and evaluated using the tri-stage procedure documented here.

  • Kim C, Mason R, Brookes TS. (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.

  • Kim C, Mason R, Brookes TS. (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.

  • Kim C, Mason R, Brookes TS. (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
  • Mason R, Kim C, Brookes T. (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 7729
    Full 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.

  • Williams D, Brookes TS. (2009) 'Perceptually-motivated audio morphing: softness'. Audio Engineering Society Convention Proceedings, Paper 7778, Munich, Germany: AES 126th Convention
    Full text is available at: http://epubs.surrey.ac.uk/712916/

    Abstract

    A system for morphing the softness and brightness of two sounds independently from their other perceptual or acoustic attributes was coded. The system is an extension of a previous one that morphed brightness only, that was based on the Spectral Modelling Synthesis additive/residual model. A Multidimensional Scaling analysis, of listener responses to paired comparisons of stimuli generated by the morpher, showed movement in three perceptually-orthogonal directions. These directions were labelled in a subsequent verbal elicitation experiment which found that the effects of the brightness and softness controls were perceived as intended. A Timbre Morpher, adjusting additional timbral attributes with perceptually-meaningful controls, can now be considered for further work.

  • Mason RD, Kim C, Brookes T. (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 Day
    Full text is available at: http://epubs.surrey.ac.uk/2952/
  • Mason RD, Kim C, Brookes T. (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.

  • Kim C, Mason R, Brookes TS. (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 7331
    Full 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.

  • Kim C, Mason R, Brookes T. (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 7579
    Full 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.

  • Brookes TS. (2007) 'Audio Perception, Measurement & Synthesis'. London, UK: Institution of Engineering and Technology (IET) Lecture Series
  • Brookes TS. (2007) 'Engineering the Senses: Psychoacoustics'. London, UK: The Science Museum Dana Centre Sound Workshop (supported by The Royal Academy of Engineering)
  • Brookes TS. (2007) 'Spatial Psychoacoustics & Creative Engineering'. York, UK: Audio Engineering Society (AES) National Student Fair
  • Kassier R, Brookes TS, Rumsey F. (2007) 'Training Versus Practice in Spatial Audio Attribute Evaluation Tasks'. Vienna: 122nd Audio Engineering Society Convention Convention Paper 7117
  • Kim C, Mason R, Brookes T. (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 7031
    Full 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.

  • Williams D, Brookes TS. (2007) 'Perceptually-Motivated Audio Morphing: Brightness'. Audio Engineering Society Vienna: 122nd Audio Engineering Society Convention Convention Paper 7035
  • Kassier R, Brookes T, Rumsey F. (2006) 'Designing a spatial audio attribute listener training system for optimal transfer'. Paris : Sound: 120th AES Convention
    Full text is available at: http://epubs.surrey.ac.uk/518/
  • Kassier R, Brookes T, Rumsey F. (2006) 'A Comparison Between Spatial Audio Listener Training and Repetitive Practice'. San Francisco : Sound: 121st Audio Engineering Society Convention
    Full text is available at: http://epubs.surrey.ac.uk/531/
  • Brookes T, Paul M. (2006) 'Controlling the Perceived Spatial Orientation of a Reproduced Human Voice Source'. Sweden : Sound: 28th Conference of the Audio Engineering Society
  • Murphy D, Brookes T, Brereton J. (2006) 'SpACE-Net - The Spatial Audio Creative Engineering Network'. Sweden : Sound: 28th Conference of the Audio Engineering Society
  • Brookes T, Neher T. (2005) 'Perceptually Unidimensional Control of Spatial Audio: a Pilot study'. London : Sound: DMRN One-day Workshop
  • Brookes T. (2005) 'The Spatial Audio Creative Engineering Network'. London : Sound: DMRN One-day Workshop
  • Kassier R, Lee HK, Brookes T, Rumsey F. (2005) 'An informal comparison between surround-sound microphone techniques'. Barcelona : Sound: 118th AES Convention
    Full text is available at: http://epubs.surrey.ac.uk/514/
  • Kassier R, Brookes T, Rumsey F. (2005) 'A pilot study into listener training for spatial audio evaluation'. Glasgow : Sound: DMRN Summer Conference
  • Brookes T, Treble C. (2005) 'The effect of non-symmetrical left/right recording pinnae on the perceived externalisation of binaural recordings'. Barcelona : Sound: 118th AES Convention
  • Mason R, Brookes T, Rumsey F. (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
  • Mason R, Brookes T. (2004) 'Perception, measurement and synthesis of spatial impression'. London : Sound: Audio Engineering Society British Section Lecture
  • Mason R, Brookes T, Rumsey F. (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

  • Kassier R, Brookes T, Rumsey F. (2004) 'A simplified scene-based paradigm for use in spatial audio listener training applications'. San Francisco : Sound: 117th AES Convention
  • Brookes T, Mason R. (2004) 'Perceptually Motivated Measurement and Control of Digital Music'. York : Sound: The Future of Audio: Digital Music in 2010 (DMRN Conference)
  • Mason R, Brookes T, Rumsey F. (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
  • Supper B, Brookes T, Rumsey F. (2004) 'A lateral angle tool for spatial auditory analysis'. Berlin, Germany : Sound: 116th AES Convention
    Full text is available at: http://epubs.surrey.ac.uk/537/
  • Mason R, Brookes T, Rumsey F. (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 Science
    Full 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

  • Neher T, Brookes T, Rumsey F. (2004) 'Unidimensional simulation of the spatial attribute 'ensemble depth’ for training purposes - Part 2: creation and validation of reference stimuli'. Berlin, Germany : Sound: 116th AES Convention
  • Neher T, Rumsey F, Brookes TS, Craven P. (2003) 'Unidimensional simulation of the spatial attribute 'ensemble width' for training purposes'. Amsterdam: 114th Audio Engineering Society Convention preprint 5769
  • Neher T, Brookes T, Rumsey F. (2003) 'Unidimensional simulation of the spatial attribute 'ensemble depth' for training purposes. Part 1: pilot study into early reflection pattern characteristics'. Banff, Canada : Sound: AES 24th International Conference on Multichannel Audio, pp. 123-137.
  • Brookes T. (2003) 'The Psychoacoustics of Sound Recording'. London : Sound: The Future of Digital Music Research (Digital Music Research Network Workshop)
  • Supper B, Brookes T, Rumsey F. (2003) 'A new approach to detecting auditory onsets within a binaural stream'. Amsterdam : Sound: 114th AES Convention
    Full text is available at: http://epubs.surrey.ac.uk/539/
  • Mason R, Brookes T, Rumsey F. (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
  • Brookes T. (2002) 'The Institute of Sound Recording'. London : Sound: Digital Music Research Network Launch Day
  • Mason R, Brookes T, Rumsey F. (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 24
    Full text is available at: http://epubs.surrey.ac.uk/7055/
  • Neher T, Brookes T. (2002) 'Training of Listeners for the Evaluation of Spatial Sound Reproduction'. Munich, Germany : Sound: 112th AES Convention,
    Full text is available at: http://epubs.surrey.ac.uk/533/
  • Brookes T. (2001) 'A speech-based frequency scale'. Amsterdam: 110th AES Convention
  • Brookes TS. (1999) 'What Does the Mind's Ear See?'. Oslo, Norway: 6th International Conference on Systematic and Comparative Musicology
  • Howard DM, Tyrrell AM, Brookes TS. (1997) 'Spectrography by Human Hearing Modelling'. 22/03/1997: Audio Engineering Society 102nd Convention preprint 4485
  • Tyrrell AM, Brookes TS, Howard DM. (1997) 'T9000 and T800 transputers: A real-time application'. ELSEVIER SCIENCE BV JOURNAL OF SYSTEMS ARCHITECTURE, COMO, ITALY: Euromicro Conference 95 43 (1-5), pp. 341-344.
    doi: 10.1016/S1383-7621(96)00077-X
  • Brookes TS, Tyrrell AM, Howard DM. (1996) 'Musical Analysis using a Real-Time model of Peripheral Hearing'. Hong Kong: Proceedings of the International Computer Music Conference (ICMC), pp. 79-82.
  • Brookes TS, Howard DM, Tyrrell AM. (1995) 'T800/T9000 Communications: A Programmer's View'. IOS Press (Oxford) Harrogate, UK: Transputer Applications and Systems '95: Proceedings of the 1995 World Transputer Congress, pp. 18-28.
  • Brookes TS, Howard DM, Tyrrell AM. (1994) 'Simulations of the Human Peripheral Hearing System: A Comparison of T800 and T9000'. Nottingham, UK: Proceedings of the VIII P.L.U.G. Conference, pp. 17-24.
  • Brookes TS, Howard DM, Tyrrell AM. (1994) 'A T9000 Simulation of the Human Peripheral Hearing System'. London, UK: Institution of Electrical Engineers Digest 208, pp. 4.1-4.4.

Posters

  • Brookes T, Hummersone C. (2010) Machine Listening for Sound Quality Evaluation. Machine Listening Workshop 2010, Queen Mary University of London
    Full text is available at: http://epubs.surrey.ac.uk/2925/
  • Hummersone C, Mason R, Brookes T. (2010) A perceptually–inspired approach to machine sound source separation in real rooms. University of Surrey Postgraduate Research Conference
    Full text is available at: http://epubs.surrey.ac.uk/7250/
  • Evans W, Mason R, Brookes T. (2010) A system for the auralisation of synthetic sound scenes using headphones and head-tracking. University of Surrey Postgraduate Research Conference
    Full 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

  • Conetta R. (2011) Towards the automatic assessment of spatial quality in the reproduced sound environment. University of Surrey
    Full text is available at: http://epubs.surrey.ac.uk/39628/

    Abstract

    The research in this thesis describes the creation and development of a method for the prediction of perceived spatial quality. The QESTRAL (Quality Evaluation of Spatial Transmission and Reproduction using an Artificial Listener) model is an objective evaluation model capable of accurately predicting changes to perceived spatial quality. It uses probe signals and a set of objective metrics to measure changes to low-level spatial attributes. A polynomial weighting function derived from regression analysis is used to predict data from listening tests, which employed spatial audio processes (SAPs) proven to stress those low-level attributes. A listening test method was developed for collecting listener judgements of impairments to spatial quality. This involved the creation of a novel test interface to reduce the biases inherent in other similar audio quality assessment tests. Pilot studies were undertaken which established the suitability of the method. Two large scale listening tests were conducted using 31 Tonmeister students from the Institute of Sound Recording (IoSR), University of Surrey. These tests evaluated 48 different SAPs, typically encountered in consumer sound reproduction equipment, when applied to 6 types of programme material. The tests were conducted at two listening positions to determine how perceived spatial quality was changed. Analysis of the data collected from these listening tests showed that the SAPs created a diverse range of judgements that spanned the range of the spatial quality test scale and that listening position, programme material type and listener each had a statistically significant influence upon perceived spatial quality. These factors were incorporated into a database of 308 responses used to calibrate the model. The model was calibrated using partial least-squares regression using target specifications similar to those of audio quality models created by other researchers. This resulted in five objective metrics being selected for use in the model. A method of post correction using an exponential equation was used to reduce non-linearity in the predicted results, thought to be caused by the inability of some metrics to scrutinise the highest quality SAPs. The resulting model had a correlation (r) of 0.89 and an error (RMSE) of 11.06% and performs similarly to models developed by other researchers. Statistical analysis also indicated that the model would generalise to a larger population of listeners.

  • Brookes TS. (1997) A Real-Time Auditory Spectrograph. University of York, UK

Teaching

Tim's teaching focuses on acoustics and psychoacoustics (as well as employment preparation, as part of his role as Senior PTP Tutor).  

Current students can book tutorials via the following link: