Design Considerations for Effective Distance Learning
Sight and sound are crucial elements in the success of distance learning classrooms. However, there is much more to consider than just the types of audio and video equipment to be used. Proper classroom acoustics, good speech intelligibility, clear sightlines, proper lighting, and seating arrangements all need to be considered when developing an effective distance learning classroom, which will benefit students and instructors alike.
What makes for effective distance learning? Considering that distance learning is really a type of conversation between two or more people, the key components tend to take on a new look. Elements that would be considered ideal room attributes include:
- Quiet, well-isolated space with low reverberation time
- Few or no windows
- Controllable lighting, preferably designed for distance learning
- High volume, low velocity HVAC
- Gasketed doors or vestibules
- Fixed desks or tables and tiered seating
- Unobstructed sightlines and camera angles
- Appropriate finishes
Let's discuss these components and look at how best to accommodate each one within a distance learning environment.
The best microphones on the market may be installed in a classroom, but without proper acoustics, these microphones will not cure speech intelligibility problems. Studies have shown that poor acoustics that cause noise disturbance and speech intelligibility problems in classrooms can lead to lower test scores. According to "Acoustical Design - Basis of a Sound Education", a School Planning and Management report from April 2005, "Students in today's classrooms are unable to understand 25 to 30 percent of what their teacher said because of excessive noise and reverberation." Distance learning classrooms are certainly no exception to this. In fact, in distance learning there is not one classroom, but the near end and far end classrooms that can be affected by poor acoustics. What acoustic issues need to be considered when planning a distance learning space? It is as easy as A - B - C:
"A" = Absorption: Reverberation Control
"B" = Background: Building Systems Noise Control
"C" = Construction: Sound Isolation
Reverberation is the enemy of understanding speech clearly. The ANSI/ASA S12.60-2010 standard, Acoustical Performance Criteria, Design Requirements, and Guidelines for Schools, Part 1: Permanent Schools, recommends a reverberation time of under 0.6 seconds for classrooms with an enclosed volume less than or equal to 10,000 cubic feet and under 0.7 seconds for classrooms with an enclosed volume between 10,000 cubic feet and 20,000 cubic feet. To control reverberation, adequate absorption must be installed in the classroom to alleviate sound from reflecting off multiple surfaces and leading to a buildup of reverberant energy. Acoustic ceiling tiles and wall panels are commonly used in classrooms to aid with good acoustics in addition to building a room with non-parallel surfaces (wall to wall, ceiling to floor) to keep acoustic energy from "bouncing" back and forth between walls. Some often-used materials that can aid in absorbing excess acoustic energy include fabric wrapped fiberglass panels, fabric drapes, carpet, and acoustic ceiling tiles.
Building systems, such as HVAC, fluorescent lights, fans, air valves, and diffusers, can cause background noise problems. If these systems are clearly audible in the classrooms, they can potentially lead to difficulty in understanding speech. Sensitive microphones can also pick up building system noises and transmit them to the distant learning space. When creating a distance learning classroom within an existing facility, curing noise from building systems can be one of the most difficult acoustic problems to solve. Careful consideration must be given to upgrading existing systems to quieter systems whenever possible to provide an overall quieter classroom.
Distance learning classrooms must also have adequate sound isolation to keep exterior noises from intruding into the classroom. It is ideal to place such classrooms away from bathrooms, elevators, HVAC compressors, and other noise-producing motors and/or plumbing. If this is not possible, then the rooms should be designed with walls, floors, and ceilings with Sound Transmission Classification (STC) ratings that can effectively reduce or block the intruding noise. STC is a numeric rating of how well a building partition attenuates airborne sound. Here are some examples of STC ratings and partition types:
Additionally, noise from busy corridors and/or noise from outside the classroom, such as traffic, can easily penetrate into the classroom from under and around doors and windows. Door gaskets and the use of acoustically rated windows can cut down on the amount of noise leaking into the classroom from these sources.
One of the often-overlooked aspects of distance learning is good eye contact. Like any other type of conversation, people are more comfortable when they can clearly see the other person's face. In addition, research has shown that when we cannot understand someone, due to either a hearing impairment or difficulty in understanding an accent, we tend to rely on watching the other person's mouth to see how he or she is forming words in an attempt to better understand him or her. This is, in essence, an unconscious form of reading lips. This would be nearly impossible if we could not clearly see the speaker's face. So how interactive does the distance learning session need to be and who needs to see whom? Here are some questions to consider that will drive design decisions such as camera layout, seating layout, and lighting design:
- Is 100 percent interactivity expected?
- Does everyone need to be seen clearly?
- Will some participants be passive?
- Will some participants be moderators?
- Will only the instructor need to be seen?
If only the instructor needs to be seen, then the camera and seating layouts become simplified. Depending on classroom size, flexible seating on a flat floor and a single camera location can be sufficient. However, in larger classrooms and in instances where the instructor and students need to be seen, then permanent tiered seating and two or more camera locations will need to be considered.
Seating is not the only issue that must be considered when developing good viewing. The room lighting must be designed to be both people- and camera-friendly. The following are some examples of what to keep in mind regarding lighting and the lighting environment:
- Glare: The correct types of lighting fixtures and the proper placement of those fixtures can reduce glaring lights in eyes, lens flare in the cameras, and veiling reflections on projected images that lead to a reduction of image contrast. Specific distance learning and video conferencing lighting equipment has been developed to help alleviate these issues.
- Room finishes and reflectance: The selection of materials and finishes for wall panels, ceilings, and furniture must be video-friendly to avoid moire effect and reflective glare. It is recommended that walls have 40 percent to 60 percent reflectance and ceilings have 70 percent to 80 percent reflectance. In general, the wall finishes and furniture should be very neutral in color and neutral blues and grays should be used for wall and camera background surfaces to improve the video separation of flesh tones in displayed and transmitted images. It is ideal for the reflectance value of these colors to be around 30 percent to 40 percent.
- Contrast ratio, environment to people: For peoples' faces to be clearly seen, it is important to have good contrast between the flesh tones of the face and the surrounding surfaces so that participants do not blend into the background. For the front wall, the contrast ratio should be approximately 4-5:1, while the side and back walls should be around 3-4:1.
Additionally, lighting should come from an angle between 45 and 60 vertical degrees. Horizontally, light should also be cast on the face from an angle in addition to from the front. This will assure that minimum shadows are created in the eye sockets and under the nose and chin. Direct overhead lighting will lead to the brow casting shadows on the eye sockets creating a "raccoon effect." Overhead lighting can also lead to the nose casting shadows over the mouth making it difficult to decipher lip movement.
The absence or presence of windows in the classroom should also be considered. The mixture of natural and artificial light in a room with windows can create problems, since most cameras balance for one type of light or the other. Mixing the two types of light will lead to the colors not appearing true.
Typically, schools are forced to use an existing facility to create a distance learning classroom. While this is certainly possible and does provide a low-cost alternative to building a new facility, there are some potential expenses that could drive the price above the projected costs. These expenses are related to retrofitting the room to create the most effective room for distance learning, as outline above.
Here are some issues to take into account when determining project costs for repurposing an existing room for distance learning:
- Low background noise (Noise Criterion 25 or NC25) often requires low velocity, high capacity HVAC design.
- Isolation from external noise may require specialized wall constructions, and window and door gasketing.
- Reverberation requirements of less than 1 second will require special wall and ceiling treatments.
- Exterior windows are problematic for light control.
- Specialized videoconferencing lighting may require specialized ceiling design.
- Tiered seating may be required in larger venues for proper viewing and flat seating may not work.
- Keep in mind that not all rooms are ideal for distance learning and the costs to retrofit may exceed the costs of building a new space. When determining if an existing room is suitable for distance learning, it is helpful to consider this partial list of possible physical constraints:
- Ceiling too low for planned group size
- Displays too small or too low - poor legibility
- Proper camera angles are difficult to achieve
- Near site audience not visible to far site
- Existing HVAC noise too loud
- Microphones not audible
- Poor speech intelligibility
- Existing lighting not appropriate
- Overhead fluorescence causes near site audience to have "raccoon eyes" shadowing
- Body language difficult to interpret
- Existing plan and/or ADA requirements do not allow tiered seating
- Sight lines are poor for students
- Faces are not visible to near or far site
Technology for distance learning evolves quickly, but the physical requirements have remained generally the same. Though it is important to stay abreast of the latest technology when developing a distance learning classroom, it is equally important to carefully plan the space. Even the latest and best technologies cannot overcome physical problems inherent in a room.
Linda Gedemer, LEED AP, CTS, Assoc. AIA, is a senior consultant at Acentech Inc., a multi-disciplinary acoustics, audiovisual systems design, and vibration consulting firm with offices in Cambridge, Mass., Trevose, Pa., and Westlake Village, Calif.