The human auditory system is equipped with two inputs - left and right ears.
This “binaural” processing system provides us with the ability to localize where sound is coming from, something that a one-eared listener would have difficulty in doing.
Playback systems may utilize any number of channels to surround the listener with sound, but two channels is always enough to simulate the human listener.
Recording enthusiasts have long discovered the benefits of stereo microphones. While not necessarily “human-like,” they can produce recordings that add spaciousness and realism to the recorded material.
Two-channel acoustic measurements are important for the same reason - they add a human characteristic to the data.
For our discussion here, I’ll use the term “binaural” to describe recording processes that provide data for two ears - there is no need to distinguish between making a recording and making a measurement, as either or both could be of interest.
Let’s look at some of the ways to get binaural data. Many modern measurement platforms support two-channel recording. We will assume that one of them is being used, allowing our discussion to be confined to microphone techniques.
One of the first decisions that must be made by the data gatherer is whether accuracy or realism is more important.
After a little consideration, it becomes apparent that one cannot have both. Setup parameters that provide a more accurate view of the loudspeaker’s response will require that the effects of the environment be minimized.
On the other hand, if the effect of the room is to be considered, then accuracy will need to be sacrificed to include it.
The question becomes, “Do I want to know what is actually happening, or do I want to know what is perceived to be happening?”
The answer to this question will fundamentally affect the method used to collect the data.
It’s important to note that at least three responses are being gathered in the recording - the loudspeaker, the listener and the room.
The listener’s response is a constant. The ear/brain system is assumed to be processing sound the same way at every seat. The loudspeaker’s response can be dramatically position dependent, but it does not have to be.
Loudspeakers that are designed for covering an audience evenly can have a similar response over a large area.