Re: phantom sources

Hi Philip,

yeah there's been quite a bit of work on this type of thing in audio research. You are also basically correct in that a phantom source will be a little broader than a real source, largely due to the fact that the localization of phantom sources is somewhat frequency dependent. Straightforward amplitude panning will produce a slight discrepancy between the localization at low and high frequency ranges, which leads to a slight change in timbre (manifests as a slight spectral dip at approx. 2kHz) and an increase in the Apparent Source Width (ASW) of the source when it is reproduced as a phantom image.

This is a big problem when dynamically panning a sound as this change in timbre tends to highlight the loudspeakers in a negative way and it significantly reduces the smoothness of the spatial trajectory (incidentally, one the main goals of the Ambisonics spatialization system was to eliminate this issue, which it largely does but not without some costs).

Ville Pullki has done a lot of research in this area, particularly in terms of his amplitude panning system VBAP. He has also conducted research on panning using three loudspeakers (again with VBAP). My recollection is that this will increase the ASW even further, and similarly reduce localization accuracy. Of course there is a strong relationship between the two factors, and the concept of locatedness is useful in this regard.

Anyway, chapter 6 my PhD thesis has lots of specific references in terms of listening tests with phantom sources and the relationship between localization accuracy and apparent source width, both for stereophony and ambisonics. You can find it here -> http://endabates.net/academic.html

Hope that helps,

Dr. Enda Bates

Music & Media Technology,

Trinity College Dublin

On 26 July 2014 16:45, William Yost <William.Yost@xxxxxxx> wrote:

Fine work in Journal of the Acoustical Society of America by Wes Grantham

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On Jul 25, 2014, at 9:17 PM, "Philip Robinson" <philrob22@xxxxxxxxx> wrote:

Howdy y’all,

I’m doing some investigations preliminary to implementing a room acoustics auralization system and want to get some input from the community.

Is there any good literature on the perceptual difference between a phantom source (e.g. between a stereo pair) and a real source (e.g. center channel)? I am interested in more than just simple localization: width, resolution of multiple phantoms, etc.? Is perception of a phantom source the same when panned between a triad or a pair of loudspeakers? My basic understanding is that phantom sources are wider or blurrier than real ones, has this been specifically tested?

Any opinions or references are welcome.

Have a great summer,

Philip W. Robinson

Environmental Design Analyst

Specialist Modelling Group

Foster + Partners

Riverside, 22 Hester Road

London SW11 4AN

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