At 10:56 AM -0500 8/5/09, Curt Olson wrote:
>
>
>Rob Danielson wrote:
>
>>>> Curt, are you using that height with your array with the 2nd
>>>> boundary on the bottom?
>>>
>>> Yea, but let's not go into that here. ; )
>>
>> Could be a pretty big factor though as the hard boundaries that are
>> fairly parallel to the ground in that array reflect more "above the
>> horizon" sound. I would expect it to respond to height changes very
>> differently from free air rigs and and arrays that have vertical
>> boundaries like SASS and the other boundary arrays you developed.
>
>That's right. I noticed this "sweet spot" only very recently when
>using the multi-boundary array. Haven't followed up yet with any other
>rigs. Frankly, until Greg mentioned the same thing yesterday, I had
>assumed the phenomenon might be peculiar to my rig.
>
>>>> Over all types of surfaces?
>>>
>>> To my ear, both near and distant sounds seem to stand out somewhat
>>> more distinctly in the small zone I referred to as the "sweet
>>> spot." I suspect one reason might be that, as Greg noted, certain
>>> types of background noise such as traffic noise, might be slightly
>>> reduced. If that's the case, then I would further suspect that it
>>> might have something to do with the happy accident of desirable
>>> phase cancellation that might occur at certain distances above the
>>> surface, and to which certain microphones or types of arrays
>>> respond in a way that some of us find to be pleasant.
>>
>> If there is advantageous phase cancellation or other ways the low
>> frequencies become attenuated, you should be able to detect the
>> nature of these changes, dynamically, with some fully-enclosed
>> headphones and hand-holding the rig as you lower it from head-height
>> to the ground.
>
>Yea, that's exactly what I've done. I'm thinking the changes are
>subtle enough that static recordings made at various heights would
>probably not be very helpful. It's most easily detected dynamically in
>real time. And again, I gotta think that different mics and different
>mounting schemes will likely respond in altogether different ways than
>what I'm reporting.
>
>> Would be instructive to do this over different ground types such as
>> short grass, large smooth slabs, patches of bare ground, tall grass,
>> brushy undergrowth, etc.
>
>I have not yet made an effort to test these different surface types.
>Will tuck that away for future outings.
>
>> When the ground is absorbing sound waves, I think it is accepted
>> theory that lowest frequency sound sources are less affected than
>> the higher frequencies that are often more helpful in creating
>> spatial clarity. The ratio of sound waves coming directly from
>> distant sources compared to those influenced by the ground is also
>> smaller with near to ground placement. However, considering the
>> larger scale, we're only discussing a ~4 change in height with
>> subject to mic distances being much larger. If you and Greg are
>> producing recording where any technique is improving spatial
>> clarity, its definitely worth looking at the specifics and trying to
>> figure out how its happening. We might need some field tests to get
>> the the bottom of it. Rob D.
>
>Thank you for always pushing us toward more clarity and better
>understanding!
>
>Curt Olson
>
>PS: Did you capture any recordings in BC that you're willing to share?
>
Hi Curt--
I'd guess your array is playing a key role too.
Embarrassingly, we got caught in a technical/legal snag over expired
passports and couldn't go. U.S. Canadian policy changed in June. The
airline process only asked for passport numbers and I didn't suspect
anything (though I should have checked anyway). Even more
frustrating, the small town "connection" airline would not let us
board even though Northwest Airlines said there was a grace period
and we'd be allowed to pass at the border. Oh, were we disappointed.
Without unpacking, we drove the next day to Upper Peninsula Michigan
which was very nice. Nothing spectacular to share so far as I go
through material. I'll post some examples to be sure. I'm quite
happy with the NT2000->MP2->H2 rig with the possible exception that I
think I can detect a little "crustiness" in (rare, slightly under
"0") peaks with the H2's A-D. I really like how simple the button
operation of the H2 is and it handled the data from the 11+ hour
takes flawlessly. I ran the MP2 external preamp at full bore in quiet
settings and the extra saturation from the H2's sensitive line input
seems like it can be a plus. Rob D.
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