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 New York, NY, 2018-10-19
The meeting was convened by chair Peter Mapp.
In attendance were P Mapp, R Cabot, B Olson, D Murphy, E Brixen, M Ramakrishnan, N Sebastian, T Welti, P Treleaven, D Weinberg, K Graffy, N Shaw, D Blore, R Kosman, S Kummer, L Fincham, J Britto, F Schaefer, M Fransois, S Hutt, K Ono, S Raghunandan, B Harris* (* denotes electronic link).
The formal notice on patent policy was read.
Minutes of previous meeting in Milan, 2018-05-24 were approved.
AES-X218: Measurement and calibration of sound systems in rooms.
PM reminded the group that in Milan it had been decided to break the document/work into 4 parts as this had a better chance of being more manageable /achievable. The sections are :
(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
PM noted that whilst some material had been submitted via the reflector, the content and format of most of this was not suitable for direct use. In Milan, it had been hoped that a volunteer had been found to produce the framework and initial text for item (1) measuring the acoustic properties of the room. However, whilst some useful references had been found, the framework and text had not really progressed. However, it had become clear to PM that the AES document needed to be a stand-alone one, without the need to continually refer to other standards. Equally, whilst other useful ANSI and ISO standards did exist (and to a certain extent SMPTE) these were not written from an audio perspective. Nortest NT ACOU 108 … was also another potentially useful document.
PM concluded that it was clear that no real progress would be made until a framework/document outline and some draft (placeholder) text had been produced, that could then be commented on. In order to get this moving, PM agreed to produce this initial document but it was then for others to take ownership of the various sections and complete the text – PM stated very clearly that he was not going to produce the complete document singlehandedly. Hopefully with some text in place it would be easier to allocate further work and the contributors would be able to better see what was wanted. PM also made the point that he expected ALL committee members to actively participate and contribute, otherwise there was no point in them being there! Furthermore, whilst it is useful to receive comment with regard to topics either not covered or insufficiently covered (or inaccuracies within the text), in order to be considered, the missing text or corrections should be supplied (at least in part) as per the procedures of other standards bodies. The meeting agreed that it would be a lot easier to react to some initial text than a blank sheet of paper. Rich Cabot [RC] noted that he was available to assist with editing/ formatting the document once the basic technical content had been established. PM welcomed this, but made the point that initially he was not concerned about the formatting/elegance of the document, he just wanted to get the basic information contributed / text written.
PM reiterated that the idea of the standard was to be able to go into a room or enclosed space and perform a set of standardised practical tests to characterise the space and the system. At this point it was not intended that the document would be a step by step guide but a set of nominal measurements with outline guidance as to how they should be carried out. This would then lead to a standardised procedure such that if three people say went into a room, they should, within reason/normal measurement tolerance, produce a similar set of results / characterisation. It was again noted, that the methods / procedures / objectives relate to enclosed spaces and not outdoor environments /exterior noise assessment.
(It has yet to be decided what the output of the group will be e.g. standard, Information or Technical report).
The point was raised about the potential overlap with other standards being written by InfoComm/Avixa. It was noted that the AES document would be tackling the issue from a rather different perspective and would not be anything like as prescriptive. It was to provide the method for carrying out the measurements and recommendations for which measurements to undertake, not what the results should be. PM clarified that the AES document was not about certifying a room or system – though the document might comment on typically expected values for a given application. However, these were not to be considered as being mandatory but merely being there for guidance. It was noted that there is no standard or code of practice / technical guide currently available that says ‘here is what you should do to measure X’ in the context of sound systems in rooms.
The size of the rooms concerned was discussed and as per the Milan meeting clarified as ranging from (a) medium sized meeting rooms (e.g. 20 people minimum), (b) Auditoria/spaces with up to approximately 2,000 seats and (c) large indoor (enclosed) spaces such as arenas/cathedrals etc. Initially, partly enclosed spaces, such as stadiums would be excluded, though many of the techniques might be applicable. Equally studios were also to be excluded. (It was agreed that at this stage it was important to narrow the scope in order to be able to make progress).
It was noted that the first step would be to work on the acoustical measurements section then move on to system measurements. The target date for the framework and initial text would be early in the New Year so that discussion could take place and the document hopefully developed prior to the next meeting in Dublin in March.
It was agreed that if any committee member had a report format or set of room analysis procedures, then it may be helpful to share these in order to expedite the writing process. PM noted that he was hoping that once the initial draft was in place, then individual committee members or subgroups could take over a particular topic and complete the text. It was also noted that if it was felt that the initial scope needed extending /changing, then reasoned and substantiated submissions would be welcomed. The chair and vice chair encouraged committee members to read the Milan meeting minutes so they were aware of the project’s direction and previous decisions. It was also agreed that the initial list of topics/parameters developed at the previous New York meeting(s) would be appended to these minutes in order to bring everyone up to speed. (PM also pointed outside of the initial meeting, no one had otherwise commented on the list or indicated any topics that were missing or should perhaps be omitted).
Currently Agreed Parameters / Topics for inclusion are :
• Frequency Response
• Sound Pressure Level (SPL)
• Max SPL
• Coverage
• Speech Intelligibility
• Distortion
• Background Noise (Acoustical)
• System Noise (Acoustical)
• Reverberation Time
• Gain Structure
• Temporal Response / Impulse Response
PM noted that it had been previously agreed that the topic of Frequency Response should be put on hold for a while as (1) It was being dealt with elsewhere (2) Considerable further research was required. Equally, until the more straight forward room acoustics parameters had been dealt with, there was no point in diluting resource trying to tackle this complex subject. However, if anyone wanted to contribute some text or reference information, then this certainly would be welcomed, but the immediate priority was to get a draft framework and initial text for the room acoustic parameters/measurement.
A brief discussion took place regarding ‘max spl’ – particularly how it might be defined and measured. It was noted that there was a direct connection with this parameter and other fields such as automobile sound systems. Steve Hutt felt that this committee would be a good forum to discuss this and potentially provide the information for an AES information document. It was agreed that this work could probably occur in parallel with the current main focus of the committee without diluting its effort. It was agreed that Steve Hutt would lead a task group on max spl and initially produce an outline and subheadings of what needed to be produced. Laurie Fincham agreed to assist. PM also pointed out that Charlie Hughes had provided some initial information on this. (It was also noted that this might be a topic for liaison with other committees e.g. SC04-03 transducers, TC AA & TC L&H).
PM noted that other task groups would be set up in due course when the main project got off the ground, but in the meantime, anyone who wanted to volunteer to lead one would be most welcome and to please get in touch.
Actions
PM to produce initial framework document and placeholder text
SH to start work on Max SPL
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 146th Convention, to be held March 2019 in Dublin, Ireland.
Virtual meetings may be held as required in advance of the Dublin meeting once some content has been developed for the group to discuss.
