Report of the meeting of the SC-04-08 Working Group on Measurement and Equalization of sound systems in rooms, of the SC-04 Subcommittee on Acoustics, held in Milan, 2018-05-24
The meeting was convened by chair Peter Mapp.
In attendance were Peter Mapp, Richard Cabot, Bruce Olson, David Murphy, Angela Coleman, Eddy Brixen, Hemam Alavi, Riccardo Crestani
The formal notice on patent policy was read.
Minutes of previous meeting in New York (2017-10-27) were approved
AES-X218: Measurement and calibration of sound systems in rooms.
PM suggested that title should be Measurement and calibration of sound reinforcement system in rooms to distinguish from other sound systems e.g. reverberation enhancement/ electronic architecture, Assistive listening etc.
PM noted that he had received several submissions as per NY meeting discussions, but whilst technically good, many were not particularly useful for the current project relating to measurements in rooms / auditoria and it was clear that the objective of the project had either been misinterpreted or misunderstood. Unfortunately due to other priorities and International standards work, he had not been able to follow up on this until now. Furthermore one of the biggest issues to overcome was how to measure the frequency response of a sound system, as there was no consensus amongst experts although this was one of the prime characteristics to measure and quantify. PM noted that SMPTE now had their standard for cinemas and InfoComm having received huge criticism on their spectral balance standard were completely re-writing it. It had previously been agreed that we wait until the InfoComm document was completed before deciding what to do with respect to this particular topic. (Shortly after the meeting, PM received a personal copy of the revision which he will study and comment on). It was agreed that B Olson would talk to Ann Brigida at the upcoming InfoComm convention.
PM’s view that we would be producing a standalone document, which whilst referencing other standards and documents would not simply tell the reader just to read them instead in order to carry out a measurement. Agreed that Nord Test 108 was a useful document – although having been written approximately 20 years ago. Discussion took place as to whether an approach might be to take this as a basis and update as this might enable progress to be made. PM pointed out that there were really two parts to the procedure (1) was measurement of the room and (2) measurement of the system. A third section might be how to report the results.
Discussion also took place concerning the number of measurement positions and the consequential time required if too prescriptive. Agreed that might have a number of examples for various types of room/ venue.
It was agreed that by breaking the project down into a number of parts that a better chance existed of actually producing a document rather trying to complete the work outright in one go. In particular, measuring the acoustic properties of the room was relatively straightforward and well known so that this could be the place to start and make some progress and break the inertia. The room measurement part could be standalone, whereas measurement of the system needed virtually all its components to be in place in order to produce a useful document. After further discussion it was agreed that the work (though not necessarily the document) could be split into four parts;
(1) Measure the acoustic properties of the room
(2) Measurement microphone placement (possibly 2 sections (a) for room acoustic measurement and (b) for sound system measurement).
(3) System measurement
(4) Reporting of the results
Angela Coleman volunteered to produce the room acoustics measurement framework / initial text.
It was also clarified that the measurements are to relate to an audience’s perspective and not the system designer’s. The type of rooms that the document is applicable was discussed. Rooms that have some form of content or performance. E.g. performance theatres, concert halls, lecture theatres/ large classrooms, traditional and modern churches and HOWs, stadiums, arenas (minimum size would be a room or space that can seat 40-50 people). Cinema / production studios, Home theatres/listening rooms are to be excluded – at least initially. Similarly not included are outdoor arenas / events and transportation terminals/hubs. Idea would be to produce a typical generic plan for each with typical microphone / measurement positions). Immersive sound systems could follow but for time being will concentrate on ‘frontal’ LR, LCR, C or distributed sound systems.
The above essentially defines the scope of the document. Definitions and references to be added as the document progresses. (It was noted that Nor test 108 was already in the group document repository). Bruce agreed to produce the document template.
It was clarified that AES standards / Documents can have colour e.g. for diagrams & graphs.
Pm noted that he hoped to start work on part 3 – but currently had an international standard (of which he is chair) and a British standard taking up quite a bit of time. However, by working on the outline this would help clarify what was needed from future contributions.
AES-X219: Method of measurement for frequency and impulse response of sound systems in auditoria
Project remains postponed, as per the 2015 NY meeting, until there is some output of X218
Liaisons
Nothing to report.
New Projects
No new projects were proposed.
New Business
No new business was proposed.
The next meeting will be scheduled in conjunction with the AES 145th Convention, to be held 17 to 20 October 2018 in New York, NY, US.
