University of Huddersfield Repository Robotham, Thomas The effects of a vertical reflection on the relationship between listener preference and timbral and spatial attributes Original Citation Robotham, Thomas (2016) The effects of a vertical reflection on the relationship between listener preference and timbral and spatial attributes. Masters thesis, University of Huddersfield. This version is available at http://eprints.hud.ac.uk/id/eprint/30196/ The University Repository is a digital collection of the research output of the University, available on Open Access. Copyright and Moral Rights for the items on this site are retained by the individual author and/or other copyright owners. Users may access full items free of charge; copies of full text items generally can be reproduced, displayed or performed and given to third parties in any format or medium for personal research or study, educational or not-for-profit purposes without prior permission or charge, provided: • The authors, title and full bibliographic details is credited in any copy; • A hyperlink and/or URL is included for the original metadata page; and • The content is not changed in any way. For more information, including our policy and submission procedure, please contact the Repository Team at: [email protected]. http://eprints.hud.ac.uk/ THE EFFECTS OF A VERTICAL REFLECTION ON THE RELATIONSHIP BETWEEN LISTENER PREFERENCE AND TIMBRAL AND SPATIAL ATTRIBUTES THOMAS ROBOTHAM A Thesis submitted to the University of Huddersfield in partial fulfilment of the requirements for the degree of Master of Science by Research Applied Psychoacoustic Lab April 2016 Copyright Statement i. The author of this thesis (including any appendices and/or schedules to this thesis) owns any copyright in it (the “Copyright”) and s/he has given The University of Huddersfield the right to use such Copyright for any administrative, promotional, educational and/or teaching purposes. ii. Copies of this thesis, either in full or in extracts, may be made only in accordance with the regulations of the University Library. Details of these regulations may be obtained from the Librarian. This page must form part of any such copies made. iii. The ownership of any patents, designs, trade marks and any and all other intellectual property rights except for the Copyright (the “Intellectual Property Rights”) and any reproductions of copyright works, for example graphs and tables (“Reproductions”), which may be described in this thesis, may not be owned by the author and may be owned by third parties. Such Intellectual Property Rights and Reproductions cannot and must not be made available for use without the prior written permission of the owner(s) of the relevant Intellectual Property Rights and/or Reproductions. - 2 - ABSTRACT Early reflections play a large role in our perception of sound and as such, have been subject to various treatments over the years due to changing tastes and room requirements. Whilst there is research into these early reflections, arriving both vertically and horizontally in small rooms regarding critical listening, little research has been conducted regarding the beneficial or detrimental impact of early vertical reflections on listener preference, in the context of listening for entertainment. Two experiments were conducted through subjective testing in a semi-anechoic chamber and listening room in order to assess subjects’ preference of playback of a direct sound against playback with the addition of the first geometrical vertical reflection. Program material remained constant in both experiments, employing five musical and one speech stimuli. Experiment one used a paired comparison method assessing a subjects’ preference, and perceived magnitude of timbral and spatial difference provided by a frequency independent ceiling reflection. Each comparison was followed by a free verbalisation task for subjects to describe the perceived change(s). Experiment two investigated this further by focusing specifically on subjects’ preference with a frequency dependent reflection. A more controlled verbalisation task provided a list of descriptive terms which the subject’s used to describe which attribute(s) influenced their preference. The results show that preference for playback with the inclusion of a vertical reflection was highly varied across both subjects and samples. However both experiments suggest that the main perceptual attribute with which subject’s based their preference was timbre, common spatial attributes (image shift/spread) cannot be used to predict preference. Experiment two suggests that the alteration of the frequency content of a vertical reflection, may also provide a more consistent level of preference for certain stimuli. It is also shown that while certain attributes occur frequently (brilliance/fullness) for describing preference, others less frequently used (nasal/boxy), may influence preference to a greater extent. - 3 - CONTENTS Title Page .......................................................................................................... - 1 - Abstract ............................................................................................................ - 3 - Contents ............................................................................................................ - 4 - Figures .............................................................................................................. - 7 - Tables ............................................................................................................... - 8 - Equations .......................................................................................................... - 9 - Notation ............................................................................................................ - 9 - Acknowledgements ........................................................................................ - 11 - Chapter 1 ........................................................................................................ - 12 - INTRODUCTION ......................................................................................................................... - 12 - 1.0 Introduction ........................................................................................................................ - 12 - 1.1 Scope of This Thesis .......................................................................................................... - 12 - Chapter 2 ........................................................................................................ - 15 - LITERATURE REVIEW ............................................................................... - 15 - 1.0 Introduction ........................................................................................................................ - 15 - 2.1 Control of Reflections in Studios ....................................................................................... - 16 - 2.2 Objective Metrics ............................................................................................................... - 17 - 2.2.1 Reverberation Time ...................................................................................... - 18 - 2.2.2 First and Early Reflections ........................................................................... - 19 - 2.2.3 Early to Late Reflections .............................................................................. - 20 - 2.3 The Effects of Early Reflections ........................................................................................ - 22 - 2.4 Perception of Lateral Sounds ............................................................................................. - 25 - 2.4.1 Spatial Impression ......................................................................................... - 26 - 2.4.2 Apparent Source Width ................................................................................ - 27 - 2.4.3 Listener Envelopment .................................................................................... - 28 - 2.4.4 Early Lateral Reflections And Timbre .......................................................... - 28 - 2.5 Perception of Vertical Sounds ........................................................................................... - 31 - 2.5.1 Detection of Vertical Reflections ................................................................. - 32 - 2.5.2 Vertical Localisation .................................................................................... - 35 - 2.6 Perceptual Assessment ...................................................................................................... - 39 - - 4 - 2.6.1 Attribute Scaling............................................................................................ - 39 - 2.6.2 Attribute Descriptions ................................................................................... - 42 - 2.7 Summary ............................................................................................................................ - 45 - Chapter 3 ........................................................................................................ - 47 - REFLECTION MODELLING ....................................................................... - 47 - 3.0 Introduction ........................................................................................................................ - 47 - 3.1 Initial Measurements.........................................................................................................