Hi John,
Your right. The value in DIY recordists using consistent materials for a sp=
ecific design is in comparing results, and objectively testing changes in p=
arameters.
Beyond that, it has little to do with getting a great recording. If it soun=
ds good, keep doing it.
John Hartog
rockscallop.org
--- In "John Crockett" <> wrote:
>
> Or I have the right stuff and we all have the right stuff! Of course the =
"right" stuff is whatever results in a pleasing, high resolution sonic imag=
e in whatever context the recording will be used.
>
> It's interesting to me that the green foam I bought looks and feels just =
like the mattress foam I have at home. But the green foam is attenuating hi=
gh frequencies at 1dB per inch and I cannot detect any attenuation at all w=
ith the same thickness of mattress foam. Something is going on in the cell =
structure of the foam that is invisible to my eye. Both are clearly open ce=
ll and of similar density. Mysterious.
>
> I measured the attenuation by simply playing a 2000 Hz signal on my compu=
ter and measuring the SPL with a sound level meter, with and without the fo=
am covering the sensor (microphone) of the meter. The same could be done wi=
th a mic and recorder, measuring the dB difference in Audacity or whatever.=
The SPL meter is just easier. I don't know if that is a legit method, but =
it did reveal the difference between the green foam and the mattress foam. =
I am going to search for another foam source, maybe even go to a junkyard a=
nd try to get some car seat foam. That looks denser to me, but will it be m=
ore acoustically dense? Only one way to find out at this point.
>
> BTW, my green foam, at 1.5 lbs per cubic foot density, is similar to the =
foam linked to on the diyboundarymic blog. So maybe it is the "right" stuff=
. Just not identical to what Crown is using, which may be proprietary.
>
> best
>
> John Crockett
> Westminster, Vermont
> The Overflight State
> --- In Peter Shute <pshute@> wrote:
> >
> > So does this mean you've got the the wrong stuff, or that we've all got=
the wrong stuff?
> >
> > How do I make this measurement? If I record a sound source with and wit=
hout it covered by the small piece I have, won't I pick up lots of reflecte=
d sound from other directions?
> >
> > Peter Shute
> >
> >
> > --------------------------
> > Sent using BlackBerry
> >
> > ________________________________
> > From:
> > To:
> > Sent: Fri Jul 13 09:13:09 2012
> > Subject: [Nature Recordists] Re: Foam for SASS
> >
> >
> >
> > Hmmm. By this test, my green foam fails. Using a SPL meter, I am measur=
ing about 1dB per inch attenuation of a 2 kHz signal. Maybe I need to keep =
looking for the right foam. I'm not confident this green stuff is going to =
adequately separate the channels.
> >
> > John Crockett
> > Westminster, Vermont
> >
> > --- In <naturerecordists%40yahoo=
groups.com>, Paul Jacobson <pj@> wrote:
> > >
> > > The SASS patent indicates that the foam for the nose should attenuate=
frequencies above 1200hz by at least 3dB per inch. All you need to do is t=
est for that property.
> > >
> > > cheers
> > > Paul
> > >
> > > On 12/07/2012, at 5:42 AM, Peter Shute wrote:
> > >
> > > >
> > > > It would be good if someone could come up with an objective test fo=
r identifying this stuff. I was told I should be able to blow through it, b=
ut with more difficulty than with medium density foam, which I wouldn't cal=
l an objective test unless I had several samples to compare.
> > >
> > >
> > >
> > >
> >
> >
> >
> >
> >
> >
>
|