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Microphone Applications for Meeting Facilities

Microphone selection is crucial By Michael Pettersen

This is the first in a series of articles about microphone and automatic mixer applications for meeting facilities such as boardrooms, courtrooms, city council chambers, and legislative chambers.

Audio for meeting facilities is a topic that encompasses a wide range of applications, from a simple public address system in a courtroom to a multi-channel legislative system with recording and broadcast capabilities. Though these systems may vary in size and complexity, they are all governed by the same physical principles and they share certain types of equipment.

Common components of these systems include microphones, automatic and non-automatic mixers, power amplifiers, loudspeakers, and many types of electronic signal processing devices such as equalizers, compressors, and audio time delays. A complete audio system may involve some or all of these items. Proper selection and application of this equipment requires knowledge of both the intended purpose of the sound system and the characteristics of individual components.

The scope of this series is limited to the selection and application of wired microphones, wireless microphones, and microphone mixers for meeting facility sound systems. However, since microphones and mixers act as the interface between the sound source (the talker) and the sound system, it is necessary to include some discussion of these two areas, and sound in general. The objective is to provide you with sufficient information to understand how microphones and mixers are applied to meeting facility sound situations. 

Sound Source
The sound source most often found in meeting facility applications is the speaking voice. Voices may be male or female, loud or soft, single or multiple, close or distant, etc. Pre-recorded audio from video or audiotape is also very common in a meeting facility.

In addition to these desired sound sources there are certain undesired sound sources that may be present: building noise from air conditioning, buzzing light fixtures, noise from meeting participants, sounds from street or air traffic, etc. All these undesired sounds can interfere with the desired sound source.

In this context, the loudspeakers of the sound system must also be considered as a sound source. They are a desired sound source for the meeting participants, but an undesired source for microphone pickup. Feedback (an annoying howl or ringing sound) can occur in any sound system if microphones "hear" too much of the loudspeakers.

Finally, the acoustics of the room are often as important as the sound source itself. Room acoustics are a function of the size and shape of the room, the materials covering the interior surfaces, and even the presence of the human bodies, which absorb sound. The acoustic nature of an area may have a positive or a negative effect on the sound produced by talkers and loudspeakers before the sound is picked up by microphones or heard by listeners. Room acoustics can absorb and diminish some sounds while reflecting or reinforcing other sounds. The latter can contribute to undesired sound in the form of echo or excessive reverberation. In general, intelligibilty problems caused by room acoustics must be solved by acoustic means, not electronic means.

In review, sound sources may be categorized as desired or undesired, and the sound produced may be further classified as direct or ambient. In practice, the "soundfield" or total sound in a space will always consist of both direct and ambient sound except in scientific "anechoic" chambers or, to some extent, outdoors, when there are no nearby reflective surfaces.

This article was written by Michael Pettersen, Director of Shure Incorporateds Applications Engineering department. It was republished from the Shure educational guide, ?Microphone and Automatic Mixer Applications For Meeting Facilities.

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Related Keywords:Audio, meeting facilities, microphone, automatic mixer applications, boardrooms, courtrooms, city council chambers, legislative chambers, presentation


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