> <General problem with them all is they are fixed, meaning the offending
> sample is presented, its filtered out and that small section is applied for
> the rest of the recording.>>
>
> That's not really how noise reduction algorithms work. The standard model
> divides the spectrum into a thousand or more bands & places a threshold
> dependent gate in each band. When properly set the threshold should be above
> the residual noise but below any desirable audio. Thus, in the presence of
> good, well recorded signal the gates are all open & passing full bandwidth
> audio, which masks the presumably lower level noise. A band with noise but no
> desired frequencies is gated, or turned down in volume. Thus the algorithm is
> constantly adapting to the changing conditions of the audio signal. This CAN
> work extremely well where there is fairly low level noise & a healthy
> separation in volume between that noise & the signal being recorded. When
> noise & signal are anywhere close to one another the process breaks down &
> you can't really save the recording, as the thresholds can no longer
> distinguish noise from signal.
This is how I understand it. But I think the writer's objection is that this
process doesn't track changing -noise- levels. For example, a passing airplane
will be above the thresholds set for the ambient noise. The fact is, these
algorithms have no intelligence, they don't distinguish the sound you want from
the sound you don't want except by level-in-frequency-band. I think Cedar has
some automatically adapting algorithms, but I doubt they'd be effective on
nature sounds.
> << Whats really needed is a temporal EQ where EQ is present at a specific
> granularity, every second, minute, or right down to milliseconds and blended
> between 'temporal EQ frames'. Tracking / learning EQ with noise reduction -
> except Ive not found one yet :( Even EQ plug'ins applied on a track affect
> that track while its active, imagine if you could blend frames of EQ over the
> whole track adjusting for situations where e.g traffic volume increases or
> decreases. Or maybe such a thing exists?>>
>
> Every automatable EQ fits this description, although you run into audible
> artifacts when automating filter sweeps very quickly. Several seconds, rather
> than milliseconds, is a preferable time frame for moving a high pass filter
> to cut occasional instances of offending traffic rumble, though often an
> ultra quick move to catch a wind gust can be made to not sound too unnatural.
Yes.
-Dan
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