Listening to an animated TV show and some dialogue was spoken directly behind the camera, and it sounded perfect. My mind immediately understand the direction of the sound.
What exactly is changed to help make the mind perceive the sound is behind us?
In: Biology
So, we only have two ears, meaning just from the perspective of two equal sensors spaced apart, we can tell if something is coming from the left or right based on which side the sound is louder on, but NOT whether it’s coming from the front or the back, because a sound 1 meter in front will have the same loudness as a sound 1 meter behind.
BUT.
There’s another factor: the shape of our ears. Our ears are this cupped flap shape that catches sound differently from the front than from the back. This alters the frequency of the sounds in a certain way, and our brain interprets that as being from in front or behind. By similarly morphing the frequencies of sounds in post (or using special microphones with ear-shaped attachments), recording engineers can create the illusion of in front or behind.
Now engineers can use digital processing to add delays and frequency shift to make it seem like sound is coming from anywhere. In the past, some engineers have gone so far as to place microphones inside an anatomical correct mannequins head and ear canals to record exactly what the sound would be at the ear drum instead of just in open air on a mic stand.
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