This page contains some extended explanations about the TCM-1 calculator, in particular the Room Acoustics setting, and some details about the example recordings.
Room Acoustics setting
The Room Acoustics setting in the TCM-1 calculator is intended to allow the user to qualitatively estimate the quality of the acoustical environment in which the microphone(s) will be installed. Five preset settings are offered for Room Acoustics: Poor, Fair, Good, Great, and Perfect. When this setting is changed, it affects the maximum distance that a person is allowed to be from a microphone. Therefore, in a room that is judged to have Perfect acoustics, microphones will be spaced further apart (since it is assumed that talkers can be further from the microphone and still sound acceptable). In a room that is judged to have Poor acoustics, microphones will be spaced closer together (since it is assumed that talkers must be closer to the microphone to sound acceptable).
The two primary factors that affect the subjective assessment of acoustic quality in a room are Noise Floor and Reverb Time. Noise Floor is a measure of how loud the background noise in the room is when it is at rest, measured in A-weighted decibels (dbA). The louder the Noise Floor, the closer a talker will have to be to a microphone to be understood. Reverb Time is a measure of how reverberant a room is, measured as RT60. This is a measurement of how many milliseconds it takes for the reverberant field of a room to decay by 60dB after an impulse sound (like a clap). The higher the Reverb Time, the closer a talker will have to be to a microphone to be understood.
Below is a table that roughly outlines what Biamp recommends as the desired Noise Floor and Reverb Time of each of the five preset Room Acoustics settings. The last column of the table also shows what the TCM-1 calculator uses as the maximum mic-to-talker distance in each of the five preset modes.
|Room Acoustics setting||Noise Floor||Reverb Time (RT60)||Max. Mic-to-Talker Distance|
|Poor||more than 45 dBA||more than 1000 ms||2 meters (6.5 feet)|
|Fair||39-45 dBA||500-1000 ms||2.5 meters (8 feet)|
|Good||37-39 dBA||400-500 ms||3 meters (10 feet)|
|Great||35-37 dBA||300-400 ms||4 meters (13 feet)|
|Perfect||less than 35 dBA||less than 300 ms||5 meters (16.5 feet)|
Biamp has created some sample recordings with the TCM-1 Beamtracking™ microphone in various acoustical spaces. These recordings are intended to demonstrate what the TCM-1 might sound like from different distances, in spaces that have differing reverberation and noise levels. Each recording has been normalized to provide a stable listening volume, therefore a recording at 1 meter will be a similar volume to a recording at 5 meters.
Note that speech quality and speech intelligibility are heavily affected by the noise level and reverb time of the space. As noise levels and reverb times increase, the maximum distance that a talker can be located from the mic (and still be understood) will decrease. For most cases, Biamp doesn't recommend locating a microphone further than 5 meters (16 feet) from a talker, even in spaces with superior acoustics. In spaces with more typical acoustics, limiting distances to 3 meters (10 feet) is a good rule of thumb.
Each recording is available either unfiltered (i.e., what it sounds like directly out of the microphone) or phone-filtered (i.e., what it sounds like after going through the typical filtering that a phone system would apply to it)