Should be unobtrusive. I am using an inexpensive Radio Shack cassette tape recorder. The sound quality is not so good. Need to manipulate the sound file using a program like SoundEffects-remove extraneous sounds and dead spaces. Otherwise the sound file must be downloaded.
Sound files occupy a lot of disk space.
A semesters worth of lectures may be about 100 Meg of RealAudio. Students and others must have appropriate computer equipment for sound. There is a time cost to students to listen to sound files. The idea of breaking the lectures into smaller segments is to facillitate the listening problem. Of course the genius of Real Audio is that down loading of the sound file is not necessary.