开云体育

On Thu, Mar 25, 2021 at 08:29 PM, n4buq wrote:

Is there an analogy between this subject and the way noise-canceling
headphones work? I'm sorry if that's a silly thing to introduce into this
conversation but it might help me understand this a bit better (or not).

There certainly is, in a way, between the title of this thread and noise-canceling headphones:

In noise-canceling headphones, a fraction of the outside environmental noise is in anti-phase added to (effectively subtracted from) the intentional sound (music, speech) and the result is produced by the speakers in the headphone; a nice example of negative feedback. The system works within a limited frequency-dependent amplitude band.

The electronics' automatic adjustment usually is audible for a short period after putting on the headphones and when changing its position on the head, causing some sort of audible "sinking in" impression.

The noise-canceling headphones' circuits can not remove oreven reduce noise present in the signal as fed from the source. OTOH, many noise-canceling headphones have a limited frequency response, effectively forming a low-pass filter for all audio, giving a noise-suppressing effect but that's got nothing to do with the noise-canceling "mechanism" itself.

Raymond