FINAL YEAR INVESTIGATION

Transcription

1 2011 SOUND, LIGHT AND LIVE EVENT TECHNOLOGY Phillip Coyne, Meyer Sound (2002) FINAL YEAR INVESTIGATION

2 Sound & Light Engineering, Live Event Technology Phillip Coyne Proposal for An acoustical investigation of the Kedleston Road Atrium and the use of beam steering speakers to create an intelligible Public Address system I. AIMS OF THE PROJECT 3 II. PROBLEM DEFINITION 4 III. PLAN OF WORK 5 IV. REFERENCES 6 V. ETHICS FORM ATTACHMENT 1 7 VI. RISK ASSESSMENT ATTACHMENT 2 8 Page 2 of 8

3 I. Aims of the Project This Independent Engineering Project aims to prove that a beam steering Public Address system (PA), will be more intelligible than the current PA system which is installed in the University of Derby's Kedleston Road, Atrium. The first aim of this Investigation is to define what intelligibility is and why it is so important in a PA system. The investigation will then explain how beam steering speakers function and why this technique can be applied to Public Address. An acoustical assessment on the construction and environment of the atrium will need to be carried out. Once this has happened, the investigation will explain why a beam steering PA system would be more successful than the current installation by comparing data and research before installing a temporary beam steering system and performing intelligibility tests using speech transmission index methods (STI). The current PA system will undergo the same tests in order to obtain a fair comparison. Below is two panoramic photographs of the Kedlston Road Atrium, ( 2011). Summary of aims 1. Define what is meant by speech intelligibility and explain why it is so important 2. Explain how beam steering speakers function and why this technique can be applied to Public Address. 3. An acoustical assessment on the construction and environment of the atrium. This will include an explanation of Absorption coefficients and how sound behaves in an enclosed space 4. Explain why a beam steering PA system would be more successful than the current installation by comparing data and research. 5. Perform Speech Transmission Index tests on a temporary beam steering installation and the current PA system Page 3 of 8

4 II. Project Definition The University Of Derby's Atrium is a public space located at the University's Kedleston Road campus. Constructed from concrete, glass and steel the Atrium houses shops, eateries, public seating and serves as a hub for the entire campus. Almost all staff and students based at the Kedlston Road campus will pass through the Atrium several times every day. A loudspeaker system designed for Public Address should be perspicuous in ALL areas that are intended for broadcast. In the case of an emergency, or even a change of platform at a train station, it is essential that any broadcasted information is fully understood because misinterpreted information could easily lead to exacerbating a situation. Intelligibility is therefore paramount when installing a PA system otherwise there is very little point in having one at all. The current PA system in the Atrium is scrutinised as part of a year two assignment by students of Sound, Light and Live Event Technology at the University of Derby. This project does intend highlight flaws or to prove that current system is not up to standard, but to use the current system as a comparison for the relatively new approach of using beam steering speakers in a Public Address system. According to P. Mapp, in Ballou (2002) "Just because a sound is audible does not mean to say that it is intelligible. Audibility relates to the ability of a listener to physically be able to hear a sound, whereas clarity describes the ability to detect the structure of the sound. In the case of speech, this means hearing the consonants and vowels correctly in order to identify the words and sentence structure and so give the speech sounds intelligible meaning". This statement defines what is meant by intelligibility in a PA system and describes exactly what the beam steering system aims to do; Provide clarity all over the atrium. If this is to be achieved then tests will need be carried out in order to log the results as proof of its success. According to the paper "THE MEASUREMENT OF SPEECH INTELLIGIBILITY" by Herman J.M. Steeneken; "In general two principally different assessment methods may be applied". These methods are Subjective and Objective. Subjective testing requires human participation which is difficult to organise within this investigations parameters. Objective testing requires equipment which can be obtained through the University. A frequently used Objective method is STI (Speech Transmission Index), Steeneken's paper states that "The STI is a measure that is based on the generation and analysis of an artificial test signal that replaces the speech signal. The result of the analysis is an index that ranges from 0 to 1. The STI accounts correctly for band-pass limiting, noise, reverberation, echoes, and non-linear distortion. STI is standardized by IEC standard (version 2, 1998)" McCarthy (2007) asks the question "If we array to speakers together, what will be the combined coverage angle?" McCarthy then goes to state that "The combined angle will begin with the individual patterns, but the end result can range from half as wide to twice as wide". This is how beam steering is accomplished, by arraying speakers together in a particular fashion in order to achieve more precise directivity. This investigation will need to determine What kind of speaker array(s) will be needed and how manipulate them into achieving the required directivity for intelligible sound in the Kedleston Road Atrium Despite a budget of approximately 75.00, this investigation is not expected to cost anything at this point. All equipment used will be from the University or borrowed through a University contact. Any costs that may occur during the investigation will be addressed as they arise and explained in the project log book. Page 4 of 8

5 III. Plan of Work STEP 1, Intelligibility and the PA system Almost serving as an introduction, the first step is to outline some basics. A brief description and explanation of what Intelligibility is, how important it is in a public address system and the relationship between environment and quality. STEP 2, The use of beam steering speakers for a PA system Step two will be the foundation of the investigation, this section provides a detailed explanation of beam steering speakers; What they are, how they work, how much they cost and how they can be used to create and intelligible PA system. STEP 3, Acoustical evaluation of the atrium This will provide a comprehensive overview of the environment and provide essential information to explain the intelligibility test results of the current PA system and the proposed beam steering PA system. This information will also be used to explain the theory of how the beam steering speakers will behave in the atrium. STEP 4, Propose Method of testing This step will outline the different testing techniques that will be used in the investigation. Namely Rapid Speech Transmission Index (RASTI) and Speech Transmission Index (STI). In order to clarify how these tests work, they will be carried out on the current PA system. This will also provide a series of fair results which can be used for comparison when the tests are carried out on the beam steering system STEP 5, Propose method of installation for beam steering PA system Using the data collected up to this point in the investigation, decisions on how to install the proposed PA system will be determined. STEP 6, Install and test beam steering speaker PA system at the atrium The installation and testing of the proposed beam steering system should be the defining step in this investigation. All research and work should have led up to this point and the results from this step will determine how successful any predictions are. STEP 7, Conclusion The conclusion will draw on all aspects of the investigation, all information must be contemplated and used to explain the investigations findings. The outcome of the investigation must be definite and clearly rationalised in the conclusion with all aspects being definite and final when compared to the research undertaken. Page 5 of 8

6 IV. Reference list References for websites Alphabetical order refers to the domain name when author is unknown. DYNASTAT, INC. ((not given)). Speech Intelligibility. Available: Last accessed 03/10/11. (2011). Virtual tour of the atrium. Available: Last accessed 01/10/2011. PB Associates. (2009). Acoustics and sound propagation: Part 1. Available: Last accessed 01/10/2011. References for books Peter Mapp. (2002). Designing for speech intelligibility. In: Glen, M. Ballou Handbook for sound engineers. 3rd ed. Oxford, OX2 8DP: Focul Press BOB McCARTHY. (2007). Combination. In: focul press SOUND SYSTEMS: DESIGN AND OPTIMIZATION. 2nd ed. Oxford, OX2 8DP: Meyer Sound. (2002). The Problem Back Lobes. DSP Beam Steering with Modern Line Arrays. 1 ( ), 3. Herman J.M. Steeneken. ((?)). The Measurement Of Speech Intelligibility. (?) ((?)), 1-8. Page 6 of 8

7 V. ATTACHMENT ONE; ETHICS FORM Page 7 of 8

8 VI. ATTACHMNET TWO; RISK ASSESSMENT Page 8 of 8