Caldwell Michael S, Lee Norman, Bee Mark A
Department of Ecology, Evolution, and Behavior, University of Minnesota, 140 Gortner Laboratory, 1479 Gortner Ave, St. Paul, MN, 55108, USA.
Department of Biology, Gettysburg College, McCreary Hall, 300 North Washington St, Gettysburg, PA, 17325, USA.
J Assoc Res Otolaryngol. 2016 Aug;17(4):259-70. doi: 10.1007/s10162-016-0568-6. Epub 2016 Apr 28.
In contrast to humans and other mammals, many animals have internally coupled ears that function as inherently directional pressure-gradient receivers. Two important but unanswered questions are to what extent and how do animals with such ears exploit spatial cues in the perceptual analysis of noisy and complex acoustic scenes? This study of Cope's gray treefrog (Hyla chrysoscelis) investigated how the inherent directionality of internally coupled ears contributes to spatial release from masking. We used laser vibrometry and signal detection theory to determine the threshold signal-to-noise ratio at which the tympanum's response to vocalizations could be reliably detected in noise. Thresholds were determined as a function of signal location, noise location, and signal-noise separation. Vocalizations were broadcast from one of three azimuthal locations: frontal (0 °), to the right (+90 °), and to the left (-90 °). Masking noise was broadcast from each of 12 azimuthal angles around the frog (0 to 330 °, 30 ° separation). Variation in the position of the noise source resulted in, on average, 4 dB of spatial release from masking relative to co-located conditions. However, detection thresholds could be up to 9 dB lower in the "best ear for listening" compared to the other ear. The pattern and magnitude of spatial release from masking were well predicted by the tympanum's inherent directionality. We discuss how the magnitude of masking release observed in the tympanum's response to spatially separated signals and noise relates to that observed in previous behavioral and neurophysiological studies of frog hearing and communication.
与人类和其他哺乳动物不同，许多动物具有内部耦合的耳朵，其功能是作为固有的定向压力梯度接收器。有两个重要但尚未得到解答的问题：拥有这种耳朵的动物在嘈杂和复杂声学场景的感知分析中在多大程度上以及如何利用空间线索？这项对科普氏灰树蛙（雨蛙）的研究调查了内部耦合耳朵的固有方向性如何有助于空间掩蔽释放。我们使用激光振动测量法和信号检测理论来确定在噪声中能够可靠检测到鼓膜对发声反应的阈值信噪比。阈值是作为信号位置、噪声位置和信号 - 噪声分离的函数来确定的。发声从三个方位位置之一进行广播：正面（0°）、右侧（+90°）和左侧（-90°）。掩蔽噪声从青蛙周围的12个方位角中的每一个进行广播（0至330°，间隔30°）。噪声源位置的变化平均导致相对于共定位条件有4 dB的空间掩蔽释放。然而，与另一只耳朵相比，在“最佳聆听耳朵”中检测阈值可能低至9 dB。鼓膜的固有方向性很好地预测了空间掩蔽释放的模式和幅度。我们讨论了在鼓膜对空间分离的信号和噪声的反应中观察到的掩蔽释放幅度与先前关于青蛙听力和通信的行为和神经生理学研究中观察到的幅度之间的关系。
