http://soundcloud.com/freitojos/20120401t0600z-bestan-a-river
Hello,
Here is one recording that in the first five or six seconds is without hig=
h pass filter 700 hz and all the rest with the high pass filter. The ms set=
up mkh 30/40 was put near a huge wall in the grass near the soil 60cm, agai=
nst the wall 100 cm. with a very deep litle river in front with the microph=
ones pointed to the open space. Can somebody explain the ressonance in the =
first seconds? So the next time I can think to optimize the position of the=
microphones. I think is something similar to the situation with the walls =
that David descrives.
Thank you,
Jos=E9
--- In "Avocet" <> wrote:
>
> I moved my MKH416 pair the other day to near my tree-laden garden as
> the dawn chorus is now hotting up. When I have time to go through the
> hours of recording I'll get some up on my web page.
>
> I had a prop plane fly past high up and as the drone dropped in
> frequency, the level shot up and hit near max level at one point. I
> measured an exact peak frequency - 108.6Hz. I couldn't work out what
> caused this resonant point. Protective mic tent no, too soft, mic
> fault perhaps? It was only on the left mic but I couldn't think of
> anything that would cause such a high-Q ringing resonance and remain
> stable. I went out and hummed at the mic rig at around 108'6Hz but
> there was no resonance at all.
>
> It took my old brain some time to work it out. That mic was looking
> towards the house and 108Hz is equivalent to about 3 metres. There is
> a single storey extension which produces two flat vertical walls about
> 3 meters apart. The plane sound must have produced an "echelon effect"
> from the two walls. There ia no other obvious explanation.
>
> Now I know what to listen for, the left mic does have a small bass tip
> up in the general background LF noise and I can compensate for this.
> However, it is an example of somtimes very noticeable effects we can
> get from nearby objects.
>
> David
>
> David Brinicombe
> North Devon, UK
> Cogito cogito ergo cogito sum - Ambrose Bierce
>
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