Re: Blind Source Separation by Sparse Decomposition ("Richard J. Fabbri" )

Subject: Re: Blind Source Separation by Sparse Decomposition
From:    "Richard J. Fabbri"  <fabbri(at)NETAXIS.COM>
Date:    Wed, 8 Sep 1999 18:33:45 -0400

Al, If you have ever heard (voltage comparator per my email) clipped speech (nth approximation to Licklider's "infinitely-clipped" speech) then, you know the remarkable job our hearing does perceiving the spoken word via zero-crossings. Yes, assumptions such as band limiting and zero-mean reduce the universe of possible signal reconstructions once given a measured set of zero-crossings. But, these ideas can also be appreciated as schema satisfying Time-Domain boundary conditions where the "boundaries" are the zero-crossings. My reason for proposing Binaural audition w/ clipping is probably becoming quite clear but, I will not write that reason hear. Anyone who wants to witness a startling demo of "stream segregation", otherwise known to Cherry as "The Cocktail Party Effect", should simply playback a Binaural recording thru voltage comparators and listen to those comparators through stereo headphones. While listening to these reconstructed (Binaural) spatial sources, recognize that we're not discussing theory ... we are: - Demonstrating psychoacoustics - Demonstrating source "segregation" via zero-crossings. Primarily period & interaural delay are encoded by zero-crossings. Most of the additional (directional) encoding, caused by pinnae and head diffraction, have been removed from the Binaural signals found at the L/R comparator outputs, i.e., some degradation of Front/Back and Up/Down discrimination will be experienced while listening to clipped Binaural recordings. But, can anyone explain these reconstructed spatial sources via a frequency analysis of "infinitely-clipped" (Binaural) channels? If not, then, how SHOULD we approach the CASA problem? Are there other tools and models we have ignored? Finally, there are better approaches to zero-crossing reconstruction, i.e., perceived with high fidelity but, these require a time-domain theory that will make no general progress thru our community while frequency analysis remains unquestioned. Try the above experiment. How do zero-crossings help us separate spatial sources? Can you explain this zero-crossing effect using frequency analysis? Rich

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