Following these simple rules can ensure that all students can see, hear, and learn.

Student-centered design focuses on the student and learning first, followed by the teacher and teaching. For students to learn, they must be able to see and hear the media, the teacher, and each other. Though seemingly self-evident, these goals are seldom met in traditional

classrooms. By following these 12 rules — all of them, since they are interdependent — you can improve learning in your institution.

1.FLOOR TO BOTTOM OF SCREEN For every student in a classroom, regardless of where she sits, to be able to see everything on the projection screen, its bottom edge has to be high enough to be able to be seen over the heads of other students. Though it may be impractical to ensure that a short person will be able to see over a tall person right in front of him, it is possible to establish a screen position that will allow students of average height full visibility over each other. For the average seated college student, the average height is 4 feet with the eyes located about 6 inches below, or 3 feet 6 inches. If you draw a line from the eyes of each student to the teaching wall, such that it always passes over the heads of other students along the way, you will find that everything above 5 feet 3 inches is visible to everyone. This establishes the lowest acceptable point to place the bottom of the screen.

2.SCREEN SIZE Because there is a limit to the detail that the eye can see, the screen must be large enough to ensure that students can read small text and see the fine detail in images. This drives the vertical dimension of the screen. For the material used in general-purpose classrooms, the height of the screen should be at least 1/5 the distance to the farthest seat, measured from the center of the screen. For example, let’s use a room that is 27 feet by 27 feet with the screen centered on one wall and the seats arranged in rows columns wall to wall to the back of the room. The distance to the farthest seat, which would be in either back corner, is about 30 feet, calculated using the Pythagorean formula for the hypotenuse of a right triangle. Since the center of the room is the focal point, W is divided by 2.

Dividing 30 by 5 gives the minimum screen height, 6 feet. The width of the screen depends upon the aspect ratio. The longtime standard is 4:3 (width to height), but 16:9 (also 16:10) widescreen is gaining popularity, especially where movies are to be shown. To calculate the screen width, multiply the height by 1.78 for widescreen and 1.33 for standard 4:3. For our example, the screen sizes come out to be 10.7 feet x 6 feet for widescreen and 8 feet x 6 feet for standard.

3.CEILING HEIGHT Considering rule #1, the ceiling height must be at least 5 feet 3 inches plus the screen height. Even though it may seem obvious, too many architects and AV contractors overlook this simple fact, and the screen ends up too low. For the 8- by 6-foot standard screen in our example, the ceiling height must measure at least 10 feet 3 inches. This is usually achievable in new or remodeled construction if it is included in the planning process with building systems that share the space between the suspended ceiling and the underside of the floor above. Explain to your architect that most of the ceiling can remain unaltered, but that you do need part of it raised and enough space above it to install the screen housing along the teaching wall. You don’t want to lose precious inches by mounting the housing below the ceiling. The area you need is in the shape of a triangle, from the projector to each end of the screen. Since the projector is normally mounted a little lower than the top edge of the screen, the ceiling could even be slanted to give more room for the other systems. If you absolutely cannot raise the ceiling, at least try to mount the screen housing above it.

4.VIEWING WEDGE The area where students can see the image with little loss of legibility or distortion is called the “viewing wedge.” It is a 90-degree arc the shape of a piece of pie, drawn from the center point of the screen and extending 45 degrees to each side of the perpendicular triangle. It reaches the maximum viewing distance derived from rule #2. In our example classroom, the maximum viewing distance is 30 feet (five times the 6-foot screen height), which was necessary to include the rear corner seats. The viewing wedge actually extends farther than the back wall everywhere but the corners, so that if we could bump out the back wall so that it followed the curve of the viewing wedge instead of a straight line, there would be room to add several more seats to the classroom.

Now envision the seats arranged not in rows and columns, but in a series of concentric arcs. Students seated in these new rows can see each other more easily than before, when their view had been for the most part limited to their next door neighbors on each side, plus a few more right behind them if they turned all the way around. In this new arrangement, eye contact increases significantly, leading to increased interaction and engagement. These correlate strongly with higher-level learning objectives.

Notice also that the viewing wedge narrows towards the front of the room, resulting in visually suboptimal space on either side. This space may be recovered by angling the walls inward. The result is a room shaped like the viewing wedge, a bit larger, and with the tip sliced off. The room outside the pie is available for other purposes. The pie shapes fit nicely together in a circle (like a whole pie) or side by side, alternating in direction. Any odd shaped leftovers might be used for IT or electrical closets, demonstration equipment storage,

A zoned lighting system using different fixtures allows separate lighting control over teaching and student areas. Also note that the ceiling is raised in front, maximizing screen size for optimal viewing.

seating, and so forth. Most architects love the opportunity to design a suite of these classrooms, because they can exercise some of the creativity they are so rarely permitted for the bulk of their work.

All told, classrooms which follow these rules are quite space efficient, as well as superior pedagogically.

5. THE TEACHING SPACE Allow 9 feet from the teaching wall to the front row. This accomplishes three things: it ensures that the front row is not too close to view the entire screen; it allows the instructor room to move about; and it avoids the awkwardness caused by the teacher standing right in front of students and invading their personal space.

6. MOUNTING THE PROJECTOR The throw distance for most classroom projectors is usually from 1/3 to 1/2 of the distance from the screen to the back wall, along the center perpendicular to the screen. It is based on rule #2 (screen size) and the throw ratio, which is the projector-to-screen distance divided by the width of the image produced by a given lens. Because throw ratio varies among projectors, it is important to use the manufacturer’s formula to specify the location.

Use the center of the zoom range, where the optics perform the best, and allow a couple of feet clearance in each direction for contingencies. If the optimal location conflicts with structures or items above the ceiling, there are three main ways to solve the problem: relocate the other items; pick another projector with a different throw ratio; or use an offset mount. Several manufacturers of projector mounts offer models that enable the projector to be placed off to the side of the post, enabling the projector to stay at the right location while the post makes a “detour” around ceiling obstacles.

The projector should be mounted with its lens along the screen center perpendicular at the height that requires no keystone correction or lens shift. If the projector must be mounted higher or lower, use its lens shift adjustment instead of electronic keystone correction to compensate.

7. DEALING WITH LIGHT Every media classroom should have at least two independent lighting zones, one in the front of the room near the screen that can be turned off for projection, and a second above the student seating, which is dimmable for notetaking. The goal is to match the horizontal light meter reading taken at the desktop to the vertical reading on the screen surface when projecting a white screen. This minimizes the time and effort required for the iris to adjust as the eye moves from desk notes to the screen. Choose fixtures that allow you to direct the light down the desktops without spilling onto the screen. There should be no more than five foot-candles on the screen from all sources combined, including notetaking light.

The light output from the projector, measured in lumens, must be sufficient to provide at least a 10:1 contrast ratio. Good contrast is essential to legibility and image comprehension, as well as avoiding eyestrain. To achieve this, the projector must be capable of producing a light level that’s about 10 times higher than the ambient light level. To determine the minimum number of lumens projector must produce, multiply the screen height by the screen width by 50. Try to double the number to allow for decreased light output that progresses as the lamp ages. Returning to our example, multiplying the screen height (6 feet) by the width (8 feet) by 50 results in 2,400 lumens. Currently, there are many good projectors in the 4,000 lumens range that would be good choices. There is another significant benefit to using a brighter projector: you can run it in economy mode with plenty of light, which allows it to run cooler with a longer lamp life.

8. POWERING AV GEAR All media equipment should share a single 20-amp isolated ground circuit with nothing else on it. This rule does two important things: the single isolated ground prevents “ground loops,” which can cause equipment to perform earratically, audible noise such as hum, buzz, static, and visual noise, “hum bars” that look like dark and light bans rolling slowly down the screen, and tears in the picture. This rule also ensures that there is adequate power for the AV equipment, uncontaminated by electrical noise from other electrical equipment (such as office copiers and laser printers, which create frequent power dips), and eliminates the risk of losing power in the middle of a presentation when someone plugs in a coffee pot in the next room, tripping the circuit breaker.

9. MAXIMIZING SPEECH INTELLIGIBILITY Require that all learning spaces have a STI-PA greater than or equal to .9 in the teaching area and at every student seat. STI-PA is a comprehensive measure of intelligibility on a scale of 0 to 1, which may be predicted by computer modeling and measured by test instruments. For general classrooms under 1,250 square feet and with no special problems (for example, vibratory rumble transmitted through the building structure from HVAC compressors), there are several steps you can take to maximize intelligibility:

Control reflected sound by choosing soft surfaces for the entire ceiling and the walls in the back half of the room, and hard surfaces in the front to reinforce the instructor’s voice and ability to hear students. Carpet reduces noise from foot shuffling and chair movement.

Minimize sound ingress by blocking every opening (except ventilation) in the classroom.

Minimize HVAC noise in teaching area or back rows (and no vents near the screen, as the moving air will cause the screen to undulate and make the image tiring to watch and even caused motion sickness.

10. SYSTEM COMPONENTS A typical classroom AV system consists of one or more sources feeding one or more audio or video display devices. Almost without exception, there is some form of source switching and volume control. In small systems with one to three sources and only one display device, these functions can be performed by the projector. In most other cases, a switcher is added to perform the switching function. In either case, a standardized simple user interface should provide the means of control (see rule #11).

Teachers report that the equipment they find most valuable to their teaching effectiveness includes:

Document camera (digital; XGA or better resolution, preferably with preview monitor)
Built-in computer (with accessible USB jack and instructor monitor)
DVD/CD player (preferably with a preview monitor to cue up the video)
Laptop connection (audio, VGA, network, AC outlet)
Auxiliary audio/video input connection (typically used with camcorders, preferably with preview monitor)
VHS player (used for legacy material that either has not been or cannot be converted to DVD or media file, with preview monitor)

With the growing interest in audio/video capture, consider installing a camera (or at least a clear path for signal and power cables through the instructor workstation). The instructor should wear a wireless microphone as close to the mouth as practical and on center (e.g., just below the knot on a tie, not on a lapel, which would cause the sound level to vary considerably as he turns his head from one side to the other).

11. THE CONTROL SYSTEM Control systems should be intuitive and powerful. A well-designed control system simplifies operation, prevents mistakes, and eliminates the need to adjust switches and knobs or move cables from one device to another. Volume levels are automatically reset to average values after every class, ensuring that there will always be some sound, never blasting or inaudible, yet still adjustable. Tasks that are required to perform other tasks are automatically initiated. For example, pressing the button to use the document camera turns it and the projector on, lowers the screen and window shades, previews the image on the computer monitor (or control touchscreen), and then, with another button push, sends it to the projector for the class to see.

Why is all this automation important? As the number of devices and options for each grows, the system becomes much more complicated to operate. A well-designed user interface can appear and function the same in every classroom, regardless of the make and model of the equipment being controlled; it translates the instructor’s intention into whatever command each device requires. It prevents many accidental disruptions by limiting the choices to the few basic functions required for teaching, cutting, for example, the 88-plus DVD options to the basic functions such as play, pause, stop, back, and forward, plus a “more” button to see additional commands.

12. IT REQUIREMENTS Allow for at least four data ports: one each for a laptop, control system, projector, and dedicated PC. A wall phone should be located close to the instructor workstation with a cord long enough for a technician to use on all sides of the workstation. In addition to aiding troubleshooting and giving the instructor a way to contact media support services, the phone serves a public safety function for medical or other emergencies. For many classrooms, it’s important to bring cable TV into the VCR. If there is a central security system, make sure the alarm wires are wired to the appropriate place in the room.

Malcolm Montgomery, CTS-D, CTS-I, is the founder of EduTech Consulting Services, which has offices in Los Angeles and Cincinnati and has been designated a top-tier Diamond Level Certified AV Systems Provider.