Frequencies covered by noise cancellation
On Tue, 09 Jun 2009 09:57:24 -0400, Harlan Messinger
wrote:
Don Pearce wrote:
On Mon, 08 Jun 2009 15:44:45 -0400, Harlan Messinger
wrote:
Don Pearce wrote:
Particularly interesting is the fact that at very low frequencies the
actives actually make the noise a bit louder. Once you get beyond
1kHz, of course, the active cancellers do nothing at all, while the
passives just go on getting better.
What are the units of the vertical axis?
dB of isolation.
What does it mean, respectively, for there to be negative and positive
dB of isolation? I would have understood positive dB to mean that the
noise level was worse than without the "isolation".
No, if you are talking isolation, then the more the better, Hence
positive dBs. The bit where the curve dips below the line (negative
isolation) is a frequency range in which the external sounds are
actually a little louder than they would be without the phones.
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