Δαφνη Ευτυχια Αρθουρος

I got fed up with the way so many web sites (including some people's journal styles) insist on displaying eensy weensy text so I have to hit the "increase font size" button several times (while others insist on displaying text at a perfectly reasonable size, so that it would be HUGE if I just told the browser to magnify everything), and not being able to read the speech bubbles in comic strips in any browser except Opera (which magnifies images as well as text), so I hauled up the Much Larger monitor I'd planned to use elsewhere, and plugged it in at the bedroom Debian box.

As a side effect, the differences in the waveforms from the two microphones pointing at different parts of a recorder, from my little experiment a few days ago (LJ entry, IJ entry, GJ entry -- only the LJ copy has comments so far (as expected)) became a whole lot easier to see.

A few details on these screen captures are probably in order. This was a tenor recorder with one mic (cardioid dynamic) pointed at the window from above and another (hypercardioid dynamic) pointed at the foot from below. (As noted previously, I tried switching the two microphones, and the difference in placement had a greater effect than the difference between the mics themselves, though I'd prefer to gather the data using a matched pair.) The mics were fed into a budget PA mixer, panned hard left and hard right respectively, very approximately balanced in volume at the mixer, no EQ; and sent to the "line in" jack on the back of a PC running Audacity under Linux. After capture, the stereo track was split into separate mono tracks, and both mono tracks were normalized (if I understand right, that should have fixed the volume difference left over from my attempt to balance them at the mixer). What you're looking at in the screen captures below (or if you squint really hard at the thumbnails above) is the same slice of time from both channels, two cycles worth from the middle of one note, stretched vertically so that each track took up the whole window (minus the toolbar and time strip).

Window:
 
Foot:

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"

If I post a stereo WAV file someplace, would enough of those of you who are interested a) be able to play it without difficulty, and b) be able to turn off one channel at a time to compare the two signals to each other and to the combined sound, without having to futz around trying to fiddle the speaker plug in back of your computer halfway out and such? Or should I do a bunch of cut-and-paste and make a file (WAV or MP3) that switches back and forth between the mics with a voiceover telling you what you're hearing when? [ETA: I did put up a simple stereo clip of a couple of scales with the mics panned as described above, for folks who can split it apart or turn off a channel at a time. See the comment about it.]