Why Recording Techniques Important-2
Recording Techniques …
How human ear listens a sound and how it perceives :-
It’s fundamental to how we determine the direction from which a sound is coming, in other words: to locate a sound source. This ability is called “localization”.
Two fundamental and dominant abilities allow this to happen: the difference in a sound’s “arrival time” at each ear, and the difference in sound level and quality at each ear.
If a sound is produced directly in front, behind, above, or below a person (or anywhere else in that plane), there is no difference in arrival time or level between the two ears. In these cases, our brain is able to use other information to determine the source direction – above, front, back and below all have their own unique characteristics, but, in general, they are more subtle than the lateral differences. As a result, our localization ability is much more acute in the horizontal plane than in the vertical plane.
For sounds which come from some “off-axis” direction (i.e., left or right), it arrives at one ear before the other (arrival time difference), and, because the head acts as a barrier, there is also a level difference (which varies with frequency) between the two ears.
Our brain processes these differences and determines the direction of the sound source. An everyday example of this is when somebody somewhere in a room talks to us, we are able to determine in what direction that person is.
On the other hand, our ability to process arrival time and level differences becomes seriously degraded at low frequencies. This is why, in stereo systems, it is sometimes acceptable to have only one sub-woofer rather than two. For very low tones (lower than about 70 Hz), we have a hard time knowing where the sound is coming from.
Intimately related to the level difference phenomenon is the fact that that difference becomes more significant as the frequency of the tone is raised. In other words, higher frequency tones will experience a greater loss of level as they diffract around the head and to the ear on the other side, than lower frequency tones.
The key point here is that differences in “arrival time” and sound “level” account for the majority of our sound localization ability.
