What does orthogonality mean in the context of adjacent channels in a filter bank?

First off, what does orthogonality mean in the context of adjacent channels in a filter bank?

Secondly, I am reviewing some code in which the dot product of the transfer functions of adjacent channels are being used to "test orthogonality". Is this a formal method with a name? How does it work?

• Your second question sounds like a strange method to me. The magnitude of a transfer function is nonnegative, so the dot product of two vectors that contain transfer function magnitudes will only be zero (which I would interpret to indicate "orthogonal") if one of the two transfer functions is zero everywhere. – Jason R Oct 5 '12 at 13:14
• OK, I was put off by the fact that the author of the code had called a temporary variable mag, but it turns out that it is the dot product of complex transfer functions. I have edited the question appropriately. Thanks. – learnvst Oct 5 '12 at 14:09