Van Opstal A John, Vliegen Joyce, Van Esch Thamar
Radboud University/Department of Biophysics, HG00.831//Donders Center for Neuroscience/Heyendaalseweg 135, 6525 AJ Nijmegen, the Netherlands.
PLoS One. 2017 Mar 23;12(3):e0174185. doi: 10.1371/journal.pone.0174185. eCollection 2017.
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.
人类在中矢状面（仰角）的声音定位依赖于对头部和耳廓提供的独特频谱形状线索的分析。然而，由于听觉系统事先并不知道实际自由场刺激频谱，从感觉频谱中提取仰角的问题是不适定的。在这里，我们通过引发头部朝向来自固定位置扬声器发出的具有随机形状、起伏幅度频谱的宽带噪声刺激移动，同时将起伏带宽在1.5至5.0周期/倍频程之间变化，来测试不同的频谱定位模型。六名听众参与了实验。从对各个刺激的定位反应分布中，我们通过应用最大似然估计来估计听众仰角感知背后的频谱形状线索。重建的频谱线索对于起伏带宽的显著变化是不变的，并且对于每个听众来说，它们与独特的头部相关传递函数（HRTF）有显著的相似性。这些结果与依赖于检测幅度频谱中的单个峰值或凹陷的模型不一致，也与对一阶和二阶频谱导数的局部分析不一致。相反，我们的数据支持这样一种模型，即听觉系统在鼓膜 - 听神经处的感觉输入与HRTF频谱形状的存储表示之间执行互相关，以提取感知到的仰角。
