On Fri, Oct 23, 2020 at 03:06:15PM -0400, moskowitz wrote: > My conclusion from experimenting with Harpex to generate spaced > arrays - based on comparing it to an array of mono mics - is that > Harpex's plane wave decomposition function isn't quite ready for > prime time.
Indeed it isn't. What the Harpex algorithm tries to do is to find an *exact* match for up to two sources in each frequency bin. There are two problems related to this: * If either the phases of two sources are close modulo 180 degrees, or the two directions are close to opposite, the computation becomes ill-conditioned. This means it amplifies small errors and the result tends to be inaccurate. * It doesn't allow for a diffuse residual. This is just a consequence of the maths, you can't do better starting from just first order. Starting from second order would solve this in many cases. It would also allow for some more intricate cases. Imagine a choir, spread over an 90 degrees angle, and singing unisono. It's neither a plane wave nor diffuse, but something in between, This is the sort of thing for which Harpex will fail, but which could be handled by starting from higher order input. Steven Boardman wrote: > PS don?t suppose you have a super-cardioid response of the Octamic? We could easily provide a super-cardioid response if you can define what exactly you mean by 'super-cardioid'. I assume it is somewhere between cardioid and hypercardioid. By 'cardioid' we mean the polar response that has a single zero at the back, and the same phase in all other directions. This corresponds to the 'in-phase' decoding in AMB terms. By 'hypercardioid' we mean the polar response that has the maximum directivity for the given order. In other words the one that maximises the on-axis to diffuse ratio. This is also the pattern that corresponds to the 'systematic' or 'max-rV' decoding in AMB terms. Another interesting pattern would be the one that corresponds to the 'max-rE' decoding. It is somewhere between the two ones referred to above, so that would be one way to define 'super- cardioid'. Ciao, -- FA _______________________________________________ Sursound mailing list Sursound@music.vt.edu https://mail.music.vt.edu/mailman/listinfo/sursound - unsubscribe here, edit account or options, view archives and so on.
