Nizami L, Reimer J F, Jesteadt W
Boys Town National Research Hospital, Omaha, Nebraska 68131, USA.
J Acoust Soc Am. 2001 Nov;110(5 Pt 1):2505-15. doi: 10.1121/1.1409371.
Van Schijndel et al. [J. Acoust. Soc. Am. 105, 3425-3435 (1999)] have proposed that the internal excitation evoked by an auditory stimulus is segmented into "windows" according to the stimulus spectrum and stimulus length. This "multiple looks" model accounts for the mid-duration hump they observed in plots of intensity-difference limens (DLs) versus pip duration for Gaussian-shaped 1- and 4-kHz tones, an effect replicated by Baer et al. [J. Acoust. Soc. Am. 106, 1907-1916 (1999)]. However, van Schijndel et al. and Baer et al. used few levels. A greater number of levels were used by Nizami (1999) for Gaussian-shaped 2-kHz tone-pips whose equivalent rectangular duration (D) was 1.25 ms. The DLs show the mid-level hump known for clicks [Raab and Taub, J. Acoust. Soc. Am. 46, 965-968 (1969)]. At some duration this pattern must become the "near-miss to Weber's law." To determine this duration, as well as the level-dependence of the mid-duration hump, DLs were established for Gaussian-shaped 2-kHz tone-pips of D = 1.25, 2.51, and 10.03 ms at levels of 30-90 dB SPL. The across-subject average DLs for the tone-pips rise up at mid-levels for D= 1.25 and D = 2.51 ms. The DLs for D=2.51 ms are larger, creating the mid-duration hump. At all durations, the new DLs are smaller at high levels than at low levels, consistent with the near-miss to Weber's law. DLs were also obtained here for Gaussian-shaped broadband-noise pips of D=0.63, 1.25, 2.51, 5.02, and 10.03 ms. The DLs for the noise-pip show a mid-level hump for all pip durations. The noise-pip DLs decrease as the pip lengthens, such that the plot of DL versus log duration shows a linear decline, with no mid-duration hump. Analysis of variance reveals that the mid-level hump coexists with the classical patterns of level-dependence, perhaps reflecting the existence of two level-encoding mechanisms, one that depends on firing-rates counted over single neurons and which is responsible for the classical patterns, and one that depends on the initial coordinated burst of neuronal spikes caused by rapid ramping, and which presumably causes the mid-level hump.
范·施因德尔等人[《美国声学学会杂志》105, 3425 - 3435 (1999)]提出，听觉刺激引发的内部兴奋会根据刺激频谱和刺激时长被分割成“窗口”。这种“多次观察”模型解释了他们在高斯形状的1千赫和4千赫纯音强度差阈（DLs）与短时程脉冲持续时间的关系图中观察到的中期持续时间峰值，这一效应被贝尔等人[《美国声学学会杂志》106, 1907 - 1916 (1999)]重复验证。然而，范·施因德尔等人和贝尔等人使用的声压级较少。尼扎米（1999年）对等效矩形持续时间（D）为1.25毫秒的高斯形状2千赫短时程脉冲使用了更多的声压级。DLs显示出了众所周知的短时程脉冲的中期声压级峰值[拉布和陶布，《美国声学学会杂志》46, 965 - 968 (1969)]。在某个持续时间，这种模式必定会成为“对韦伯定律的近似偏离”。为了确定这个持续时间以及中期持续时间峰值的声压级依赖性，针对声压级为30 - 90分贝声压级、D = 1.25、2.51和10.03毫秒的高斯形状2千赫短时程脉冲建立了DLs。D = 1.25毫秒和D = 2.51毫秒的短时程脉冲在受试者间的平均DLs在中期声压级处上升。D = 2.51毫秒的DLs更大，形成了中期持续时间峰值。在所有持续时间下，新的DLs在高声压级时比低声压级时更小，这与对韦伯定律的近似偏离一致。这里还获得了D = 0.63、1.25、2.51、5.02和10.03毫秒的高斯形状宽带噪声短时程脉冲的DLs。噪声短时程脉冲的DLs在所有脉冲持续时间下都显示出中期声压级峰值。噪声短时程脉冲的DLs随着脉冲变长而减小，使得DL与对数持续时间的关系图呈现线性下降，没有中期持续时间峰值。方差分析表明，中期声压级峰值与经典的声压级依赖性模式共存，这可能反映了两种声压级编码机制的存在，一种依赖于单个神经元计数的发放率，负责经典模式，另一种依赖于由快速上升引起的神经元尖峰的初始协同爆发，大概导致了中期声压级峰值。
