Example cost of materials for acoustic treatment:
Audio Sources:
Using Mackie 1202 mixer: Mix wireless microphone and PC/workstation line outputs to Alt 3/4; assign remote audio to main mix. Connect Alt 3/4 output to workstation input for distribution to remote sites. Assign Alt 3/4 to main mix [or patch it back to another stereo input], with remote audio added; connect main mix to house audio (amplifier).
Alternative: Tap remote send from AUX1 or AUX2, and set remote source (from network) to AUX zero, all other sources mixed onto AUX. Main mix goes to amplifier and recording.
Instead of or in addition to having per-student microphones, it may be possible to use a parabolic or shotgun mike on the audience camera. However, voice quality (frequency response) may be degraded.
| Student, instructor and remote microphone treated as independent multicast participants; speaker only plays remote participants | Remote audio may leak back through student microphones, although
this can be made less likely if gating is used and speaker is at front
of class. (Should not be a problem any more than acoustic feedback?)
Cannot use single echo canceller since its microphone input would have
to connect to the local mix only and feed the echo-cancelled (minus
delayed version of remote) to remote. Problem: delay.
Recording needs all network sources.
Audio tool maps local network participants to left channel, remote participants to right channel. Recording mixes both channels plus local wireless microphones, amplifier for house audio only plays right channel. If amplifier has input selector, define two channels: one that copies right channel onto both, one regular. |
| Students, instructor and remote microphone treated as independent multicast participants; per-workstation echo cancellation (such as CallPort) | Expensive; may not work as room is larger than assumption of
cubicle. Sound may leak from neighboring speaker.
|
Instead of single speaker, have two speakers sets (middle, front, and monitor for instructor)
Video sources (instructor monitor (see nv!) or selected windows, camera image of student, audience camera, document camera, camera image of instructor) must be combined into single NTSC output for recording onto tape.
One approach would display these sources on a second (640x480) monitor in the control room, manipulated by controls on the first monitor. The second monitor output is then scan-converted as usual. Windows on the second monitor would be tiled and not have decorations. This assumes that local video cameras can produce smooth 30 fps video.
In a more traditional approach, all non-student cameras and a copy of the projection monitor output are mixed by a digital video mixer.
Tablet-arm chairs: room size minus 50 sq. ft. for teaching area and divide by 15 sq. ft. per student. Classrooms with only one entrance/exit door are limited to a maximum of 49 occupants. When seats are fixed as little as 12 square feet per student may be required by code.
| depth | depth to rear corner seat | sq. ft. | students | screen size | screen width | screen height | screen mounting height | overhead projector distance |
|---|---|---|---|---|---|---|---|---|
| < 30 | 35 | 900 | 20-50 | 6' | 72" | 72" | 8.2' | 8.6' |
| 30-35 | 35-42 | 900-1200 | 50-100 | 7' | 84" | 72" | 9.25' | 10.3' |
| 35-40 | 40-46 | 1200-1600 | 100-150 | 8' | 96" | 72" | 10' | 11.8' |
| 40-46 | 46-52 | 1600-2100 | 150-210 | 9' | 108" | 78" | 10.75' | 13.3' |
| 46-52 | 52-58 | 2100-2700 | 210-300 | 10' | 120" | 90" | 11.5' | 14.8' |
| 52-58 | 58-64 | 2700-3300 | 300-400 | 12' | 144" | 108" | 13' | 17.7' |
| 58-64 | 64-70 | 3300-4100 | 400-500 | 14' | 168" | 126" | 14.5' | 20.6 |
| depth | students | front space |
|---|---|---|
| < 27' | < 30 | 9' |
| 27'-32' | 30-50 | 10' |
| 32'-37' | 50-100 | 11' |
| 37'-42' | 100-150 | 13' |
| 42'-48' | 150-210 | 15' |
| 48'-54' | 210-300 | 16' |
| 54'-60' | 300-400 | 18' |