> Can anyone tell me why all of my recordings seem to have an intense LF ru=
mble? I know that some of it is the recorder itself, as using a dummy mic s=
howed some signal at around 75 Hz, but almost all of my other recordings ha=
ve this intense low rumble starting around 200 Hz and going down. Is it dis=
tant traffic? The Hum?
Because it=92s there! Most urban environments have a huge rumble from traff=
ic near and far. Most natural environments have it too, from traffic, indus=
try, and ocean far away. I treasure the few places I can go where, in the m=
iddle of the night, there=92s only a slight LF rise.
The reason we don=92t hear it is the good old Fletcher-Munson curve. We=92v=
e evolved to filter out low-level low-frequency noise because it carries no=
helpful information for survival. We hear it in our recordings as soon as =
we turn up above natural playback level, which means every time we play bac=
k our recordings!
-Dan
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