You always hear different things in your left and right ears. When the two sounds are the same, they contradict each other so you hear nothing. But if one voice grow louder, then that voice becomes very annoying.
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From @imthewind
You always hear different things in your left and right ears. When the two sounds are the same, they contradict each other so you hear nothing. But if one voice grow louder, then that voice becomes very annoying.