> =C2=A0I forgot that it was relatively close to a major highway.
Tom,
A study showed that birds sing louder with a high background noise.
> I seemed to have problems with highway noise even when I had the micropho=
nes pointing away from the highway.
Gunmics have a lot of side lobes at different frequencies and the "gun
effect" only really works at the higher frequencies when the wavelength is=
comparable to the director tube. At 5KHz, the wavelength is around 7cms.
At lower frequencies they have a cardioid response with some really bad rea=
r
lobes. The best rejection is often around 90 deg and in real life you can
get as much as 20db less sensitivity off axis.
Now for the real story. The solid angles including up and down are also
picking up general noise but all this solid angle is less sensitive with a=
gunmic. Sometimes you can also baffle this noise with a car or your body or=
a tree and as I suggested, try putting the rig on the ground. On grass you=
can often hear a drop in the BG hubbub. Don't ask me for the theory but it=
works. I taught this trick to a generation of assistant Sound Recordists
> I was able to get a lot of the highway noise out with the =E2=80=9Chighpa=
ss filter=E2=80=9D in Audacity.=C2=A0
I make no apologies for using filters and my favourite is a gentle LF
roll-off. Many bass cuts have a sharp kink to 6db per octave but mine
doesn't. Any kink in a response produces a resonance of some sort and this=
can often be heard if you listen for it.
You can construct and edit your own filters easily in Audacity using a text=
editor. First find the file:
<EQCurves.xml>
Copy this to a safe place so you can put it back if you goof up. Here are m=
y
default bass roll-off curves (HPF) Don't be put off by it going up to 800HZ=
.
It starts to bite below about 200Hz.
You can use these filters twice or more times and undo them using the inver=
t
function.
<curve name=3D"HPF800-1-2-3">
<point f=3D"20.000000000000" d=3D"-12.700000000000"/>
<point f=3D"200.000000000000" d=3D"-3.000000000000"/>
<point f=3D"400.000000000000" d=3D"-1.000000000000"/>
<point f=3D"800.000000000000" d=3D"0.000000000000"/>
<point f=3D"22049.000000000000" d=3D"0.000000000000"/>
</curve>
<curve name=3D"HPF800-2-4-6default">
<point f=3D"20.000000000000" d=3D"-26.000000000000"/>
<point f=3D"200.000000000000" d=3D"-6.000000000000"/>
<point f=3D"400.000000000000" d=3D"-2.000000000000"/>
<point f=3D"800.000000000000" d=3D"0.000000000000"/>
<point f=3D"22049.000000000000" d=3D"0.000000000000"/>
</curve>
<curve name=3D"HPF800-3-6-9">
<point f=3D"26.000000000000" d=3D"-35.000000000000"/>
<point f=3D"200.000000000000" d=3D"-9.000000000000"/>
<point f=3D"400.000000000000" d=3D"-3.000000000000"/>
<point f=3D"800.000000000000" d=3D"0.000000000000"/>
<point f=3D"22049.000000000011" d=3D"0.000000000000"/>
</curve>
Have fun.
David Brinicombe
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