Thanks for the info. Here's a good old thread on the topic from DIYMA...If anyone is interested in some background on sound localization, I have a few articles of interest. One company that made large headway in this field was developing audible exit signage, using broadband noise to allow easily localization. Their research made it into NFPA 72 and is included in Annex D for voice evacuation (speech intelligibility and sound localization) for the preservation of life. Two of their articles are here:
\http://www.systemsensor.com/en-us/Documents/localizable_alarms.pdf
http://www.systemsensor.com/en-us/Documents/exitpoint_directional_sound_evacuation.pdf
You'll note that localization doesn't have a hard cutoff above or below a certain frequency. Instead, the spectral content of the noise is what matters. How we localize sound (IID vs ITD) has a frequency cut-off based on the physical distance between our ears.
Page 4 of this article has good graphics to illustrate this:
http://www.systemsensor.com/en-us/Documents/life_saving_directional_sound.pdf
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