On Thu, Jun 09, 2011 at 11:03:56AM -0400, jim moses wrote: > But the unanswered question is, can we really detect the originating > > direction of low frequency sound if you do not > > have assistance of the over 80-120Hz overtones ? > > > > conventional thought says no. This matches my experience. This description > from wikipedia > http://en.wikipedia.org/wiki/Sound_localization#Evaluation_for_low_frequenciesseems > pretty good to me. > > "For frequencies below 800 Hz, the dimensions of the head (ear distance > 21.5 cm, corresponding to an interaural time delay of 625 µs), are smaller > than the half wavelength of the sound waves. So the auditory system can > determine phase delays between both ears without confusion. Interaural level > differences are very low in this frequency range, especially below about > 200 Hz, so a precise evaluation of the input direction is nearly impossible > on the basis of level differences alone. As the frequency drops below 80 Hz > it becomes difficult or impossible to use either time difference or level > difference to determine a sound's lateral source, because the phase > difference between the ears becomes too small for a directional evaluation. > "
Two more (Euro)cents: Just performed a little experiment. Sine wave of 50 Hz, linear rise to full amplitude in 150 ms, hold 250 ms, linear fade out of 150 ms. The spectrum of such a signal is more than 60 dB down at 100 Hz re. its peak at 50 Hz. Panned to random directions in 3rd order Ambisonics and reproduced on the horizontal octagon at the LABEL studio (Quested SR8). I can *easily* tell from which direction it comes. There is some front/back ambiguity if (and only if) I keep my head fixed, but that is to be expected. Ciao, -- FA _______________________________________________ Sursound mailing list Sursound@music.vt.edu https://mail.music.vt.edu/mailman/listinfo/sursound
