Breno pointed out that the phase shift is probably just the length of the recorder plus the distance to the mic, divided by the speed of sound. (I think the effect of a phase shift would still be present for a single mic halfway across the room, at least if the description I recall of the sound from the foot coming out in a very narrow cone is correct, because the direct signal bounced off the floor would have a longer path than the signal direct from the window ... right? Note to self: experiment with single distant mic in rooms with and without shag carpeting.) Note that there is some sort of overtone in the sound from the window, but the sound from the foot looks "dirtier" ... er, "ripplier"
Yes, you have a time delay between the two mics due to the distance. But much "character" of the signal seen by the lower mic from the tiny echoes and reverberations inside the instrument.
Neither signal is truly what we think of as a recorders "voice", it's the combination. Hence, a mic placed several feet away and generally pointed at the recorder "mid-body" will capture a truer image of it's voice. And more of the room ambiance (sometimes a good thing, sometimes bad..).
As an aside, this is one of the fascinating differences in flutes such as recorders, tin whistles, etc. verses transverse flutes. A transverse flute generates almost zero sound energy out of the foot, resulting in quite a different mic placement for them...
By the by, I have a long list of suggested reading on the physics of musical instruments and their construction. I suppose I should post it somewhere someday...
(no subject)
Yes, you have a time delay between the two mics due to the distance. But much "character" of the signal seen by the lower mic from the tiny echoes and reverberations inside the instrument.
Neither signal is truly what we think of as a recorders "voice", it's the combination. Hence, a mic placed several feet away and generally pointed at the recorder "mid-body" will capture a truer image of it's voice. And more of the room ambiance (sometimes a good thing, sometimes bad..).
As an aside, this is one of the fascinating differences in flutes such as recorders, tin whistles, etc. verses transverse flutes. A transverse flute generates almost zero sound energy out of the foot, resulting in quite a different mic placement for them...
By the by, I have a long list of suggested reading on the physics of musical instruments and their construction. I suppose I should post it somewhere someday...
Janice