acted from the return echo. Modern echo cancellation systems are amazingly effective. With sophisticated echo cancellation systems, unidirectional microphones are no longer required. Continuous speech can be provided in both directions. Interruptions and side conversations (rude as they might be) are captured and transmitted. Audio is automatically adjusted to keep it from being too bright (too much residual echo) or too dead (no natural echo). Because they are processing-intensive, echo cancellation methods may introduce slight delays to interactive speech. It is important to work closely with a supplier or multimedia systems integrator to develop a strategy for providing high-quality audio in a conferencing facility. Modeling can cut down the work, but there is no substitute for experimenting with microphone types, quantities, and placements. One should be particularly careful if the conference room is large or if multiple microphones will be used. Background noise and reverberation (the reflection of sound waves) are cumulative if all microphones are on at once. One solution (albeit cumbersome) is to use speak-listen control systems (sometimes called push-to-talk microphones). These do not allow interruption and thereby result in a condition called capture. However, they do provide good volume and are great in large, noisy rooms with big groups. Systems are available that use automatic mixing techniques (for instance, noise adaptive threshold) to manage microphones. Speech detection circuitry provides a way to turn microphones on and off automatically, and to preclude the necessity for manual adjustment. Systems of this type give the floor to the loudest sound, even if it is something as disruptive as a sneeze. Auto adaptive technology seeks to counter such ill effects, but effectiveness varies with techniques. Some provide outstanding coverage and feedback rejection, while others deliver mediocre performance. One would be wise to arrange an installation as 30-day money-back-if-not-satisfied trial. Many speake