|Also available in Acrobat format|
Defining and Implementing Standards for Lecture Room Services
2 Physical and technical standards
2.1 The literature and internet search produced some texts and BSI/ISO standards that were used as a basis for examining the lecture room standards. A useful starting point was The Complete Guide to Electronic Presentations (Purdom, 1996). Though this was perceived as being produced for the corporate sector, a number of the basic principles adopted for the local project were based on this publication, unless otherwise stated. Another useful publication was Effective Audio-Visual Presentation (Simpson, 1987 - unfortunately at the time of writing the University's copy of the 1996 edition was unavailable). Certain BSI/ISO documents were also studied. While these were often specific to other environments and perhaps too detailed for the kind of general benchmarks being sought to examine standards for the local project, they were nevertheless invaluable. A range of manufacturers' brochures and manuals were also used containing technical data, tables, histograms, etc.. These were helpful in identifying significant physical and technical considerations. While it cannot be claimed that this literature search was particularly exhaustive, sufficient information was nevertheless obtained with which to assess some of the factors relating to lecture rooms at Brunel.
2.2 The range of presentation media likely to be used in lectures includes:
Inevitably, lecture rooms must have suitable facilities to offer projection of still and moving images, television screens, audio playback/sound reinforcement and writing boards.
2.3 Screen projection
2.3.1 There are well-established principles for determining size and type of projection screen and relationship to seating layout. An important consideration is the viewing in relation to the axis of the screen. This can vary considerably depending on the type of screen, higher gain screens tending to have a narrower viewing angle, often in the region of 30o, and decisions must be made in terms of trading-off gain against practical viewing angle. An important consideration here in the context of data projection is that brightness output from LCD projectors is still comparatively low, with the implication that a high gain screen should be used. However, this might not be compatible with a fixed seating layout with wider viewing angles and manufacturers are continually developing brighter projectors. So performance when using matt white screens, offering wider viewing angles, is likely to improve. Taking a simplistic approach so that viewing angles could be examined more practically, the following benchmark was therefore adopted:
For members of the audience to be able to view clearly, they should be seated within a 45o angle of the centre line of the screen.
This is assuming that the screen and seats are placed on a common central axis. A useful rule of thumb is that the ratio between the length of the front row and distance from front row to screen must not exceed 2:1.
2.3.2 It should be noted that if the angle of view is found to be excessive, the viewing angle can be optimised if the screen is mounted off-centre and tilted towards the seating axis. This also has the advantage of offering multiple aspect presentation, say if there is a requirement to make simultaneous use of projection, writing boards, television replay, etc..
2.3.3 It is accepted that back projection is an effective option but this was omitted from the Case Study as there are no lecture rooms in the University designed to offer back projection.
2.3.4 An acknowledged standard was also adopted relating to the fixing height of the screen to ensure good visibility and minimal disruption of the projection beam:
The bottom of the screen must be at least 1.2 metres above floor level.
2.3.5 There are also generally accepted standards for determining screen size in relation to seating:
(i) the minimum distance of audience from the screen = 2.5 x screen height;
(ii) the maximum distance of audience from the screen = 8 x screen height.
For the purposes of the local project, it was assumed that a screen's normal aspect ratio is 1:1, allowing both landscape and portrait display in aspect ratios of 3:4. While there might be occasional requirement for 16:9 display, this has been regarded as a specialised application. As screens are available in incremental heights, some suggested sizes being given in Table 1, there is a choice between adopting height of the actual screen or the height of the projected image. It was decided to adopt the proportional calculation, i.e. V/8, where V is the distance between the screen and the back row of seats. It was also possible to attribute suitable proportions for a seating block based on V:
The minimum distance between the screen and front row is V/4.
The maximum length of the front row of seats is V/2.
2.3.6 It also stands to reason that there must be no obstructions to projection from any ceiling suspensions so the following standard was included:
Maximum height of the screen depends on the height of the ceiling, seating area and the position of any suspended structures that may obstruct viewing or projection.
2.3.7 Perhaps an obvious but essential statement is `lighting control is fundamental to a good presentation' (Purdom, 1996). In order to ensure optimum projection quality, there must be sufficient and flexible control of lighting to enable a high percentage of exclusion in the immediate vicinity of the screen and an appropriate and even level for the audience to be able to take notes. Simpson indicates that lighting must be under push-button dimmer control. Whatever form of lighting control is offered it must be easy to use and clearly labelled. Curtains or blinds must be able to exclude the majority of daylight. It was considered that the ambient light level should be quantified as a standard both as a maximum for the immediate space around the screen and as a minimum for the seating area. It is intended that experiments are made in the near future to arrive at suitable levels. In summary, the following standards were therefore adopted:
There must be separate control of lighting for the audience and the screen spaces.
Lighting controls must be convenient and simple to operate.
It should be possible to achieve almost total exclusion of daylight.
2.3.8 There are several ways in which seating can be configured to offer different teaching modes but for the purposes of this exercise the important issue was thought to be whether or not the seating is fixed to the floor. If so, then services can deal with more certainties in terms of screen position, size, etc.. Unfixed seating, while offering greater flexibility for optional teaching methods, requires a similar level of flexibility to be accommodated in the installation, occasionally to the extent that more than one side of the room can be used for projection. In such situations, rail systems offer a useful means of achieving such flexibility. Suitably wide gangways must be provided for the purposes of emergency exit.
2.3.9 The quality of seating must be suitable for sustained periods of use, particularly if long sessions are the norm. Suitable platforms must also be provided for note taking. This aspect was not surveyed as part of the local project and but its importance should not be underestimated.
2.3.10 Where a lecture room has no projection booth, space must be provided for projection equipment either in front of the audience, or suspended above the seating area where appropriate. Once a suitable screen size has been determined in relation to distance V, appropriate formulae and tables given in BS ISO 11314 : 1995 may be used to determine the required location and lens specification for the projection equipment. Ideally, any projection equipment located in front of the audience should be positioned and configured to present the optimum screen size for the room. However, there may be cases where the only possible location is within the seating block. In this case adequate measures must be taken to provide a secure operating platform for the equipment, suitably managed cable runs for power supply and signal cables, and freedom from obstruction within the projection aperture.
2.3.11 Screens should be tilted to the optimum angle for the type of projection equipment being used in order to eliminate image distortions such as keystone. This requires adjustable screens when projecting from multiple locations.
2.3.12 It was necessary to categorise lecture rooms simply and conveniently for the purposes of examining lecture room installations. The following were thought to be the most useful:
Category 1 Room with fixed seating and projection booth
Category 2 Room with fixed seating an no projection booth
Category 3 Room with unfixed seating
2.4 Television screens
2.4.1 The requirements for display of moving images are different to those for data display. The Sony guide indicates that the distance between the screen and audience for video is between five and ten times the screen diagonal whereas for data it is more specifically expressed as six times the screen diagonal (Purdom, 1996). Working on the basis of minimum requirements, and assuming that the provision of screens is normally more controllable than seating distances, the following standards were adopted:
The minimum diagonal screen size for video display is V/10.
The minimum diagonal screen size for data display is V/6.
2.4.2 It follows that in situations where display requirements are determined by maximum seating distance, television screens are more likely to be used for video in smaller lecture rooms, whereas most rooms are likely to require some form of projection for data.
2.4.3 Table 1 presents a summary of the above calculations for practical application of the aforementioned principles, both in relation to minimum sizes for projection and television screens. This table enabled one to determine the minimum screen size requirements for a room given distance V.
2.5 Audio Playback and Sound Reinforcement
2.5.1 These audio aspects were examined together because a common system is likely to be required for both.
2.5.2 Before examining audio systems, it was decided to determine prerequisite standards for effective sound reproduction, i.e. appropriate room acoustics. There were two important considerations here: (i) ambient noise levels; (ii) reverberation time. Ambient noise in a room may be caused by a wide variety of sources including audience movement and chatter, equipment fans, environmental control systems, noise from adjacent areas, external noise from road and air traffic, and even lawnmowers! Clearly, the general level of ambient noise in any room must be kept to a minimum so that lectures can be clearly heard by the audience. ISO 9568:1993 Cinematography - Background noise levels in theatres, review rooms and dubbing rooms was thought to provide a useful basis for adoption for lecture rooms, although its scope is limited to steady noise within the theatre. A significant statement is that `Levels beyond NC-45 will result in poor audio reproduction', i.e. a noise curve ranging between 75dB at 31.5 Hz, through about 46dB at 1 kHz to about 42 dB at 16 kHz. It also suggests that a certain level of steady background noise is helpful in masking distracting intermittent noises. For comparative purposes, normal speech has a level of about 60 - 65 dBA and suggested isolation levels for lecture rooms range from 35 - 45 dBA (Talbot-Smith, 1995). It was difficult to produce a working benchmark here and the proposed action was to undertake measurements along ISO 9568 lines in those rooms that were perceived as having significantly intrusive ambient noise.
2.5.3 Excessive reverberation can severely affect the clarity of audio signals. Conversely, a room with excessive absorption is likely to require sound reinforcement, even in a small space, so a compromise has to be achieved. Using a suggested duration of 0.6 - 1.2 T60 for reproduced sound in lecture rooms, the following was adopted as a working benchmark (Talbot-Smith, 1995):
Reverberation time experienced in a lecture room should be in the region of one second.
It was thought that a simple clap test would be sufficient though this has yet to be applied locally. It was anticipated that results would vary depending on the number of people in the room and by variable surface area of furnishings such as curtains. Tests should therefore be made under typical operating conditions for multimedia presentation.
2.5.4 Once suitable room acoustics had been achieved would be necessary to determine what power the audio system should have and how many speakers should be provided in the room. For smaller rooms, when using LCD projectors or television monitors, internal loudspeakers are probably sufficient. For larger rooms, a separate amplification system will be required, preferably offering a mixer with sufficient channels to facilitate a suitable range of sound sources that may be used. In such cases, the following standard was adopted:
High quality separate audio amplification should be used in lecture rooms seating 40 or more people with sufficient power rating to deliver undistorted sound at a typical operating level appropriate to the room.
The range of available products and environments makes it difficult to specify a power rating but Purdom suggests that for medium sized presentations, and amplifier of 60 watts capacity will be needed. The number of loudspeakers required is related to audience size, a suggested principle being that 4 speakers will be need in rooms with a seating capacity of 50 and 8 speakers for rooms with a capacity of 100 (Purdom, 1996). Ideally, loudspeakers should enable even distribution of amplified sound throughout the seating area at a similar height to the screen. In larger rooms, it may be necessary to install an electronic delay device to maintain a perception of synchronisation for viewers seated towards the back of the room.
2.5.6 As larger rooms would require sound reinforcement and suitable microphone systems it was decided that all installations requiring separate audio amplification systems should provide sound reinforcement for the lecturer. For the multimedia age it is desirable to build in a level of audience interactivity by offering some facility to enable students to use microphone systems in addition to the lecturer. Radio microphone systems offer the greatest flexibility in terms of giving the lecturer unrestricted use of space and for the audience to pass round hand-held units. In practice, the limited availability of operating frequencies imposes a severe restriction on the number of systems that can be used simultaneously within an operating radius that effectively covers an entire site. Cable systems were thought most suitable for widespread adoption, saving radio microphones for more specialised purposes, particularly where members of the audience were involved. Also, it was thought that lecturers should be given the option to use either lectern microphones or to wear tie-clip types, depending on their needs, and cable runs should be suitably managed for safety and convenience.
Separate audio amplification systems must include a multiple microphone facility, normally via a cable, offering a suitable choice of operating modes.
2.5.7 To offer additional functionality, it was considered that:
Any lecture room audio system should include a suitable line level output facility for the purposes of recording lectures or onward transmission.
2.5.8 To provide optimum facilities for hearing-aid users, it was decided that:
All audio installations should include an induction loop system so that hearing aid users can receive the entire range of audio sources available on the system via their 'T' setting.
2.6 Spontaneous written, drawn or typed information
All lecture rooms must provide basic facilities for lectures to write or draw spontaneously during their presentations. For the multimedia age there were thought to be two applicable principles:
(i) that the media used are IT friendly in terms of minimising dust;
(ii) that a suitable range of electronic interfaces are available, including mouse keyboard.
2.6.1 By default therefore:
Chalk boards must not be used where there is also use and storage of any equipment containing electronic circuits, lenses or viewing screens.
2.6.2 As whiteboards and flipcharts would continue to be used in the foreseeable future, it was determined that such provision should be flexibly incorporated within an installation so that projection screens and television can be used simultaneously.
2.6.3 Inevitably, lectures and students would need to interact spontaneously with multimedia displays via electronic interfaces.
Data displays must incorporate suitable electronic interfaces to enable spontaneous enhancement of and interaction with any multimedia display.
2.7.1 It was thought unrealistic to adopt lasting technical standards for using computers in lecture rooms so certain operational considerations were summarised as a check list:
(i) What network facilities are available in the lecture room?
(ii) What operating system and software applications are available on the network?
(iii) Are any specialised multimedia operating platforms, operating systems, software applications and hardware required for multimedia display and if so how are they provided?
(iv) Who supplies and supports the actual computer?
(v) What display equipment will be used and what are the interface and configuration requirements?
(vi) How will user files be managed?
(vii) Are any peripheral devices required?
2.7.2 It was thought that computer network points should be conveniently provided, both for table-top access in front of the lecturer and for connection to lecture room systems. There should also be a telephone connection point available, capable of independent use when the network points are being used. This would enable reporting and 'talk-down' dialogue relating to any problems encountered during set-up, both with internal and external service providers, as well as offering other communication facilities.
2.7.3 Also, optimum display size, brightness and uncompressed resolutions should be sought at all times when projecting computer data.
2.7.4 Furthermore, the general level of LAN performance must be sufficient to handle increasing levels of demand long term.
2.8.1 It was thought that much of the operating equipment should be contained in a suitable secure cabinet to enable convenient interconnection, multiple power supply, etc..
2.8.2 Also, most controls and temporary connecting points should be readily to the lecturer as s/he faces the audience.
2.8.3 The floor must be free of any cable runs and similar hazards.
2.8.4 Adequate furniture must also be provided, not only for operating a range of equipment, but leaving sufficient table space for equipment and materials being used during the lecture.
Graphics Multimedia Virtual Environments Visualisation Contents