deally, room noise should be less than 50 dBa (where dBa refers to decibels, adjusted). Interior locations are best (street noise is not possible to control). Avoid high-traffic areas such as reception lobbies, cafeterias, bullpen environments, and heavily-used adjacent corridors. Soundproofing walls and double-glazing the windows can block ambient noise. This is worth the effort in the case of a boardroom installation but may not be in the case of roll-about or set-top systems. Acoustic treatment need not be expensive. Carpeting a room, hanging panels or drapes over windows, and placing screens in front of sound-generating equipment. Hang a partial curtain (so that it is well above people's heads when they are walking) from a high ceiling about mid-room from side to side Implementing Group-Oriented Systems to limit reflective noise. Poorly designed HVAC (heating, venting and air conditioning) systems cause ambient noise. Installations should be equipped with proper-sized fans and should be physically isolated. Older fluorescent lights (which are also notorious for generating 60-cycle-hum in sound systems), computer fans, and vibrating objects can also generate unwanted noise. Audio quality is primarily a product of the acoustical properties of the room, the amplification system, and the selection and placement of microphones and speakers. Loudspeakers should be placed at the level of the listeners' ears to create a direct path for the sound waves, and SO that reflections are minimized. Regardless of design, to some degree, User B's microphone will capture sounds from User B's speakers, and will transmit User A's audio back to him. This is an undesirable effect called direct acoustic coupling. Unidirectional microphones (that pick up sounds from one side, as opposed to omnidirectional, that that pick up sounds from all sides) are suited for conferencing because they minimize the sound picked up from the speakers and thereby reduce direct acoustic coupling. Unidirectional microphones respond differently depending 