Reconstructing spectral cues for sound localization from responses to rippled noise stimuli.
Human sound localization in the mid-saggital plane (elevation) relies on an analysis of the idiosyncratic spectral shape cues provided by the head and pinnae. However, because the actual free-field stimulus spectrum is a-priori unknown to the auditory system, the problem of extracting the elevation angle from the sensory spectrum is ill-posed. Here we test different spectral localization models by eliciting head movements toward broad-band noise stimuli with randomly shaped, rippled amplitude spectra emanating from a speaker at a fixed location, while varying the ripple bandwidth between 1.5 and 5.0 cycles/octave. Six listeners participated in the experiments. From the distributions of localization responses toward the individual stimuli, we estimated the listeners' spectral-shape cues underlying their elevation percepts, by applying maximum-likelihood estimation. The reconstructed spectral cues resulted to be invariant to the considerable variation in ripple bandwidth, and for each listener they had a remarkable resemblance to the idiosyncratic head-related transfer functions (HRTFs). These results are not in line with models that rely on the detection of a single peak or notch in the amplitude spectrum, nor with a local analysis of first- and second-order spectral derivatives. Instead, our data support a model in which the auditory system performs a cross-correlation between the sensory input at the eardrum-auditory nerve, and stored representations of HRTF spectral shapes, to extract the perceived elevation angle.
Radboud University/Department of Biophysics, HG00.831//Donders Center for Neuroscience/Heyendaalseweg 135, 6525 AJ Nijmegen, the Netherlands.
A John
http://orcid.org/0000-0001-5957-5712
AJ
Van Opstal
Radboud University/Department of Biophysics, HG00.831//Donders Center for Neuroscience/Heyendaalseweg 135, 6525 AJ Nijmegen, the Netherlands.
Joyce
J
Vliegen
Radboud University/Department of Biophysics, HG00.831//Donders Center for Neuroscience/Heyendaalseweg 135, 6525 AJ Nijmegen, the Netherlands.
Thamar
T
Van Esch
D000161:Acoustic Stimulation / Q000379:methods*; D000328:Adult; D003463:Cues; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D013016:Sound; D013017:Sound Localization / Q000502:physiology*; D055815:Young Adult