Rob Danielson wrote:
> from earlier in the string, Walt wrote:
>
>>A desirable sound for self noise
>>would be a smooth hiss, but some mics sputter or crackle. With a smooth
>>hiss, the self noise can actually be audible and not upset the listener.
>
>
> Very true. Narrow bands right around 8K are pretty common. Use a
> narrow peak or notch parametric equalizer to find these spots in all
> three files. These can be removed effectively with successive very
> narrow notches-- avoid a fat single notch if the actual noise is in a
> narrow band (~200-500Hz wide). The sputtering/uneven stuff from some
> mics falls down to 3K and is quite hard to remove without really
> making the recording sound dull. The Rode NT3's I've used have some
> sputtering noises in this range and they're rated at 16dB(A)*. I've
> seen some mics with curious narrow noise bands as low as 4700 Hz.
I understand that some DPA mics are also bad about sputtering. I've
never tested one, however.
> I'm quite sure self noise affects transparency in the low range too
> when field saturation levels in the recordings are low (~<6%). Noise
> in the low range makes its hard to balance the acoustic space
> realistically, especially in relation to individual sounds in the
> lower mid range like the human voice. Lots of folks roll-off the
> bottom end but the space pretty much disappears and its an important
> part of the field experience. I recently found that I could
> significantly boost the 125-600 Hz range in a recording made in a
> quiet location to make a tinny frog chorus sound more natural and
> less harsh on the ears. The boost added warm "air" to recordings
> when made with mics in the 16dB(A) self noise range, and worked
> really well with some mkh-20 recordings too (10dBA). But when I
> tried the boost with recordings made with my Crown PZM's (23dBA), it
> made instant grunge.
>
> The hiss does jump out first, but if you compare clarity at other
> frequencies, you may notice this too.
I agree that the low end is probably neglected in thinking about self
noise. I have found that low end noise issues are often far more
important than those high frequency ones that we generally don't hear as
well anyway, especially at my age.
It's a awful balancing act as low frequency is where distant unwanted
noise is the biggest problem. I love to have a fully complete spectrum,
but often find it essential to filter the low end.
> * The sensitivty of the Rode NT3 is 12dB(A), about 4dB less than
> some other mics with the same self noise rating I regularly use.
> Whenever the record gain is high, its easy to hear this difference in
> sensitivity because its translates into 4dB? of additional noise when
> the sound is played back at final mix level.
This is a whole 'nother aspect of the self noise equation. In what I
said, mic sensitivity was more or less ignored. But it has a bearing in
mic choice vs self noise. The better the mic sensitivity, the less you
will be increasing gain to get the meter reading you want, so the less
you will be lifting the noise floor.
It's no wonder that mics like the MKH-60 with it's self noise of 6dBA
and sensitivity of 40mV/Pa is able to do a amazing amount of dragging
clear sound in.
Walt
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