Posted by: "Barry Blesser"
> First, there is no question that an elevated microphone will produce a co=
mb
> filter frequency response because the direct signal will merge with a
> delayed version that bounces from the ground. One observes the same issue
> with office speakerphones where the microphone is as close to the table t=
op
> as possible, thereby avoiding the delayed reflection from the table top.
In the natural environment you are dealing with direct and reflected
sound no matter where you put the mic. By putting it up high you avoid
some of the reflections, particularly those that will have reflected off
something close to the mic location and be louder than those reflecting
off parts of the environment farther away.
The reflections are not as regular and organized as those off a table
top or floor, however. So calling it a comb filter is probably not proper.
> Second, the question of what constitute "natural" pops up. As adults
> standing in the field, our ears are some 5 feed above ground and we too h=
ear
> the comb filter response, but we call that natural because we expect to h=
ear
> it. However, doing a recording is different from human listening, because=
in
> the first case, the sound source and the listener are in one shared
> environment. When reproducing a recording, however, the listening
> environment may be stereo loudspeakers in a laboratory, headphones with s=
ome
> binaural processing, or whatever. There are therefore two sets of acousti=
cs:
> the source space and the listening space.
Indeed, one can make a case for only recording at standard ear height
and only with ear spaced microphones. However, microphones are not ears,
and definitely don't have the processing system we have behind them. We
process and simplify sound before we hear it. Even so far as selectively
removing reflections from individual reflecting objects. Dropping a lot
of the original sound sources entirely. Microphones don't do any of
that, and part of the challenge is to get them to duplicate in some way
our filtration of sound. One way is to simplify the soundfield with
height of the microphone. It is not the only way.
> The same issue appears when trying to record music. Even though the
> applications and goals are different, the discussion about musical space =
in
> my book, Spaces Speak, is directly relevant to all forms of recording. On=
e
> must carefully analyze the choices in the context of the specific goals.
As I've pointed out music is recorded in specifically simplified
environments with regular and organized acoustic features. Nature
recording has no such luxury.
Actually, nowadays music is often a mixture of a bunch of mono mic
pickups picking up individual instruments or groups of instruments mixed
to imitate a organized soundfield. Nature recording rarely tries this
but depends on much simpler pickups that preserve the natural cues of
the soundfield. At least that's how I approach it, one recordist, one
stereo mic setup to record the soundfield. It's quite different from
current music recording.
And that's even without considering the differences in scale. Nature
recording deals with far greater distances than music recording. Which
makes for considerable difference in technique.
Walt
|