Department of Neuroscience and Carney Institute for Brain Science, Brown University Providence, United States of America.
Speech and Hearing Biosciences and Technology, Harvard University, Boston, United States of America.
PLoS Comput Biol. 2021 Feb 17;17(2):e1008677. doi: 10.1371/journal.pcbi.1008677. eCollection 2021 Feb.
Computational models of animal biosonar seek to identify critical aspects of echo processing responsible for the superior, real-time performance of echolocating bats and dolphins in target tracking and clutter rejection. The Spectrogram Correlation and Transformation (SCAT) model replicates aspects of biosonar imaging in both species by processing wideband biosonar sounds and echoes with auditory mechanisms identified from experiments with bats. The model acquires broadband biosonar broadcasts and echoes, represents them as time-frequency spectrograms using parallel bandpass filters, translates the filtered signals into ten parallel amplitude threshold levels, and then operates on the resulting time-of-occurrence values at each frequency to estimate overall echo range delay. It uses the structure of the echo spectrum by depicting it as a series of local frequency nulls arranged regularly along the frequency axis of the spectrograms after dechirping them relative to the broadcast. Computations take place entirely on the timing of threshold-crossing events for each echo relative to threshold-events for the broadcast. Threshold-crossing times take into account amplitude-latency trading, a physiological feature absent from conventional digital signal processing. Amplitude-latency trading transposes the profile of amplitudes across frequencies into a profile of time-registrations across frequencies. Target shape is extracted from the spacing of the object's individual acoustic reflecting points, or glints, using the mutual interference pattern of peaks and nulls in the echo spectrum. These are merged with the overall range-delay estimate to produce a delay-based reconstruction of the object's distance as well as its glints. Clutter echoes indiscriminately activate multiple parts in the null-detecting system, which then produces the equivalent glint-delay spacings in images, thus blurring the overall echo-delay estimates by adding spurious glint delays to the image. Blurring acts as an anticorrelation process that rejects clutter intrusion into perceptions.
动物生物声纳的计算模型旨在确定回声处理的关键方面，这些方面负责回声定位蝙蝠和海豚在目标跟踪和杂波抑制方面的卓越实时性能。声谱相关和变换 (SCAT) 模型通过处理蝙蝠实验中确定的听觉机制处理宽带生物声纳声音和回声，复制了这两个物种的生物声纳成像的各个方面。该模型获取宽带生物声纳广播和回声，使用平行带通滤波器将其表示为时频声谱图，将滤波信号转换为十个平行的幅度阈值水平，然后在每个频率上对生成的时间发生值进行操作，以估计总体回声范围延迟。它通过将其描绘为一系列局部频率零，在对广播进行去啁啾后，沿着声谱图的频率轴规则排列，从而利用回声频谱的结构。计算完全基于每个回声相对于广播的阈值事件的阈值交叉事件的时间发生。阈值交叉时间考虑了幅度潜伏期交易，这是传统数字信号处理中缺失的生理特征。幅度潜伏期交易将跨频率的幅度分布转换为跨频率的时间注册分布。使用回声频谱中的峰和零的相互干扰模式，从物体的单个声学反射点或亮点的间距中提取目标形状。这些与整体范围延迟估计合并，以产生对象距离的基于延迟的重建以及其亮点。杂波回波不加区分地激活空探测系统的多个部分，然后在图像中产生等效的亮点延迟间距，从而通过向图像添加虚假亮点延迟来模糊整体回声延迟估计。模糊作为一种反相关过程，可以拒绝杂波侵入感知。
