Improving Audio Quality in Distance Learning Applications. (1998)

This paper discusses common causes of problems encountered with audio systems in distance learning networks and offers practical suggestions for correcting the problems. Problems and discussions are divided into nine categories: (1) acoustics, including reverberant classrooms leading to distorted or garbled voices, as well as one-dimensional audio output; (2) correct microphone usage, including creating a natural sound environment with carefully placed microphones; (3) correct loudspeaker usage, including zoning loudspeakers and balancing speaker output; (4) acoustic echo, including microphone pick-up of received audio off loudspeakers and re-transmission of audio back to the originating site; (5) outside noises, including blower/fan noises, buzz from fluorescent lighting, noises from outside the room, and paper shuffling; (6) sound system problems, including electronic and acoustic feedback; (7) telephone system feedback, including squealing and howling whenever a phone line is introduced and phone coupler problems; (8) other telephone system concerns, including listener fatigue from processing out line noise and compensating for thin, tinny audio; and (9) satellite echo, i.e., delayed repetition of voices over the satellite. Three diagrams are included to illustrate reverberation and its effects on transmitted audio, acoustic coupling generated by an open microphone and speaker, and the use of an acoustic echo canceller. (DLS) ******************************************************************************** Reproductions supplied by EDRS are the best that can be made from the original document. ******************************************************************************** U.S. DEPARTMENT OF EDUCATION Office of Educational Research and Improvement EDUCATIONAL RESOURCES INFORMATION CENTER (ERIC) O This document has been reproduced as received from the person or organization originating it. Minor changes have been made to improve reproduction quality. Points of view or opinions stated in this document do not necessarily represent official OERI position or policy. Improving Audio Quality in Distance Learning Applications Craig H. Richardson President & CEO ASPI Digital Introduction PERMISSION TO REPRODUCE THIS MATERIAL HAS BEEN GRANTED BY C.H. Olgren TO THE EDUCATIONAL RESOURCES INFORMATION CENTER (ERIC). If you're like most educators, distance learning represents a fim and interesting challenge for cr, ko you. The logistics of dealing with multiple locations and the problem of keeping everyone oo (NI interested in your topic are your main concerns. And, if the distance learning network is designed correctly, they should be your only concerns. 12.1 The problem is that in a large number of distance learning networks, careful attention is paid to the video sidecamera locations, position of the lighting, ability to view monitors, etc. but little attention is paid to the audio, which carries the bulk of your message (unless you're conducting a final exam on sign language or lip reading!). Does your distance learning network have any of these problems? Bottom of the barrel sound (the rooms sound hollow and boomy) Feedback/squealing in the PA system + Feedback/squealing whenever you bring a phone line into the conference Voices are distorted or garbled (difficult to hear or understand participants) Fans or blowers overpower voices + Some voices are too faint, others too loud Background noise is really annoying Acoustic echo (you hear your own voice coming back to you, or your students hear their own voices coming back to them) + Satellite networks: your students hear their voices coming back to them over the satellite, with a long delay + Telephone networks: the audio is thin, tinny, difficult to listen to for long periods of time You do not have to put up with bad audio in your distance learning network! This paper will discuss the most common causes of the problems encountered with audio systems, and practical suggestions for correcting the problems. It's (Almost) All in the Acoustics Here is a bold (but true) statement: Most audio problems in your distance learning network are caused by poor acoustics in the classrooms. With only a few exceptions, the majority of your problems can be traced to the hard surfaces you'll find in the classroomwalls, floors, ceiling, windows, and tables. A room with lots of parallel hard surfaces is said to be highly reverberant, meaning a sound introduced into the o room will bounce around for some time before decaying beyond your ability to hear it (see Figure 1). 0 a(z 2 Improving Audio Quality 301 But, you say, we've had reverberant classrooms ever since schoolhouses were first designed. What makes them a problem in distance learning?