At 9:55 PM +1100 10/7/09, Paul Jacobson wrote:
>
>On 05/10/2009, at 5:01 AM, Rob Danielson wrote:
>>>
>>> The high frequency complexities of the wing whirs was the first thing
>>> I noticed when I heard the unprocessed mp3 material. I'll take a
>>> listen to the original and see what else we might be able to learn.
>>> Did you reach an opinion about whether there is some "sizzle" in the
>>> recording from the vegetation? My memory of the situation can be
>>> useful in guiding tone shaping in post. Rob D.
>>
>
>> Given the amount of steady sustain and the "grainy" character of the
>> "hissy" noise, I do suspect its not just from environmental
>> vegetation/wind interaction. You can see from the EQ curve, much of
>> the noise is between 4K Hz and 6K Hz with a large concentration
>> around 4300 Hz. The amount of noise is different from channel to
>> channel and pretty fixed in ratio which also suggests its not
>> environmental. I cannot account for what others may hear above 10Hz
>> with my ears. I bet others can hear plenty up there. This noise is
>> not typical for AT-3032 recordings I've EQ'd before.
>>
>> There seems to be stridency in the loud calls in the original too,
>> but less than in the mp3. I didn't address this in interest of time.
>
>Hi Rob,
>
>I've spent a bit of time playing around with the recordings and going
>back to the quietest bit of predawn recording I can find on the Round
>Hill recording and one I made in still conditions a week earlier. I'm
>now fairly sure the difference is down to the wind and vegetation
>noise. Listening back to the raw recording the noise of the wind in
>the background is quite apparent, and the background noise during
>"silence" does seem to be primarily wind related.
>
>I've also tested the phantom voltage output of the HDP2 right down to
>shutdown. I had to unplug one mic and measure the voltage on the
>channel so it isn't a perfect test. The HDP2 finally shut down when
>the output of the external battery went below 7.5V DC. At this point
>the output of the Li-ion pack was dropping rapidly - in final 10
>minutes it went from just above 10V to shutdown level. The phantom
>voltage remained steady at 46V right until the unit powered down. I'd
>have to drag my scope out of storage to check if there is an increase
>in rail noise as the voltage drops.
>
>I'm struggling to find a clean Spiny-cheeked Honeyeater recording on
>the net as an example. Try this lowbit rate mp3 or a recording by Fred
>Van Gessel :
>
><http://www.birdsinbackyards.net/images/audio/acanthagenys-rufogularis.mp3=
>http://www.birdsinbackyards.net/images/audio/acanthagenys-rufogularis.mp3
>
>These birds have an unusual call that is quite buzzy. I commented to
>my partner during the trip that their calls made you feel like your
>ears are distorting so I'm cautious about ascribing the distortion to
>the recorder or mics.
>
>regards
>Paul
>
Hi Paul--
Although its unusual for wind/vegetative "zizz" to be so stationery
in pitch and in sound level, I trust your experience/memory of the
situation more. Now that you are alert to the phenomenon, maybe
you'll be able to figure out how it happens. It is curious, if it is
a naturally-produced sound.
As for the wing "whirr" phasing, it sounds like the Doppler effect as
the birds flies towards and away from the mics. Perhaps occurring at
higher pitches then we are accustom to. Rob D.
--
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