Hello Justin,
On 29 Jun 2011, at 12:44 pm, Justin Bennett wrote: > as I also have 2 DPA 4060-BM's and access to 2 more, I was interested in the > idea too.. > > I have two practical questions / comments > > Theoretically the mics have to be at the surface of a sphere, but > practically, the DPA omni > capsules are side-mounted - if you take the cap off they "point" to one side > with, as far as > i remember, a pressure eqalisation hole in the "back". How could one mount > such mics > so that they are "at the surface" ??? I'm not so sure the best way to deal with this one.... > and this one is for Jo: > >> Then apply BDT to the X, Y, Z. I'd also suggest using a crossover, so that >> HFs are time delays. > > how does this actually work with xyz? I know how it works in stereo - matrix > into M/S and process > each channel separately. - Are X,Y and Z channels treated all like the S > channel in stereo? > don't you need to do anything to W then? In my experiment, I treated W like M and X, Y, Z like S. Gerzon doesn't show using a crossover filter to return HFs to shadowed delays, but I found this seemed to have a better result. (You'll need to carefully match phase at the cross-over point!) For easy modelling of response on a sphere, see: C. P. Brown and R. O. Duda, “An efficient HRTF model for 3-D sound,” in Proceedings of the 1997 IEEE ASSP Workshop on Applications of Signal Processing to Audio and Acoustics, New Paltz, NY, 1997. C. P. Brown and R. O. Duda, “A Structural Model for Binaural Sound Synthesis,” IEEE Transactions on Speech and Signal Processing, vol. 6, no. 5, pp. 476-488, Sep. 1998. Chapter 4 of Etlinger's dissertation steps through the solution in discrete time: D. Etlinger, “A Musically Motivated Approach to Spatial Audio for Large Venues,” PhD Thesis, Northwestern University, 2009. Just do a quick web search for these titles, and they'll come up. You can rig your mics up on a virtual sphere, and then fool around with synthetic signals to see how the results sound. Now, admittedly, the Duda model is 'cheap and cheerful', but can give some idea. Also two chapters that could be useful to look at on the topic. The 1st chapter is pretty easy to follow: G. W. Elko, “Differential Microphone Arrays,” in Audio Signal Processing for Next-Generation Multimedia Communication Systems, Y. (Arden) Huang and J. Benesty, Eds. Boston, USA: Kluwer Academic Publishers, 2004, pp. 11-65. J. Meyer and G. W. Elko, “Spherical Microphone Arrays for 3D Sound Recording,” in Audio Signal Processing for Next-Generation Multimedia Communication Systems, Y. (Arden) Huang and J. Benesty, Eds. Boston, USA: Kluwer Academic Publishers, 2004, pp. 67-89. My best, J Anderson -------------- next part -------------- An HTML attachment was scrubbed... URL: <https://mail.music.vt.edu/mailman/private/sursound/attachments/20110708/00b0c7e8/attachment.html> _______________________________________________ Sursound mailing list [email protected] https://mail.music.vt.edu/mailman/listinfo/sursound
