I was one of those kids who put round pegs in square holes. Out-of-the box thinking didn't apply. Now I'm one of those adults... Regarding recent posts: I don't think anybody wants to listen to pink noise unless you're performing the exercises in Dave Moulton's Golden Ear training. But recordings of Gaussian, weighted, and band-limited noise are highly purposeful--we all know this.
Digital recordings of pink noise are even better than the old days of analog noise generators because we have a replicable reference that we can overlay or compare measurements to. On average, pink noise gives a predictable spectrum, but without a recording and known time reference, we can't repeat the EXACT same signal over and over--again, no news here. But here's something I wish to try (I've touched on this in past posts, but now my design is more concrete). Briefly, I propose a recording of a recording in order to validate *accuracy* of spatial reproduction. A human element need not be present (this ain't social science). By rotating my TetraMic on a fixture that permits rotation on its central axis (see figure in link below)**, I can use a single loudspeaker to create the equivalent of a circular array of n loudspeakers playing bursts of narrowband noise (or music, if you prefer). I use narrowband (octave or third-octave) noise in lieu of pink noise to improve the SNR. This recording will provide the initial B-formatted files of noise bursts. I'll arbitrarily rotate the mic in 60-degree increments for a total of 6 positions. Because a single speaker is being used, I only have to calibrate one speaker at one location. Regardless, I now have an equivalent recording of a 6-speaker, horizontal-only array. For playback, I will use a cubical array that consists of eight loudspeakers: four below the horizontal plane (plane as it passes through the mic) and four above this plane. Four of the speakers are inverted so that the speakers above mirror the speakers below. I am building a frame that permits easy mounting of the speakers. Each speaker has its own *shelf* that angles the speaker toward the center of the cube. The frame can be transported out-of-doors and away from reflecting surfaces (other than ground reflections). I work on a ranch (part-time) and is why I have ready access to an open space. Next I play the initial recording that consisted of noise bursts emanating from six virtual speakers, but the processed recording is played thru the cubic arrangement. At the center of the cube is the TetraMic. This time there this is no speaker (or speakers) on the horizontal plane passing thru the mic, but the initial recording was made from a virtual array of speakers lying on this plane. If the playback provides a true physical replication of the original recording, the resulting B-formatted files of the recording-of-a-recording should closely match the B-formatted files from the first recording in both level and spectral make-up. To a listener, the virtual surround (first recording) should appear as speakers in a circular array, each equally spaced 60 degrees apart and at ear level, when played through the cubic array. Of course, I'm assuming the listener is positioned such that his/her ears lie on the horizontal plane that passes thru the center of cubic array. But when we replace the listener with the mic, the physical wave fronts will provide objective evidence of *accuracy* in terms of spatial orientation at the listening position. If the radius of the virtual (circular) array is greater than the distance to the faces of the cube, we might also get a sense of sound-to-source distance that goes beyond the (imaginary) sides formed by the cubical array. But because distance-to-source judgments depend on familiarity of a sound or SNR, I'd rather rely on objective results obtained via this proposed iterative recording process. Maybe my idea is not original (though it is independently conceived), or even the bestest of ideas. But then, it isn't beneath me to put round pegs in square holes and do my own experimentation. Note that this experiment is void of music, doesn't require human subjects, but it is all about Ambisonics. Best to All, Eric 'Blockhead' C. **URL to photo is www.cochlearconcepts.com/for_sursound/tetra_mount.jpg -------------- next part -------------- An HTML attachment was scrubbed... URL: <https://mail.music.vt.edu/mailman/private/sursound/attachments/20130703/3cff4821/attachment.html> _______________________________________________ Sursound mailing list Sursound@music.vt.edu https://mail.music.vt.edu/mailman/listinfo/sursound
