Erbe Christine
JASCO Research Ltd., 55 Fiddlewood Crescent, Bellbowrie, Qld 4070, Australia.
J Acoust Soc Am. 2008 Oct;124(4):2216-23. doi: 10.1121/1.2970094.
This article examines the masking of a complex beluga vocalization by natural and anthropogenic noise. The call consisted of six 150 ms pulses exhibiting spectral peaks between 800 Hz and 8 kHz. Comparing the spectra and spectrograms of the call and noises at detection threshold showed that the animal did not hear the entire call at threshold. It only heard parts of the call in frequency and time. From the masked hearing thresholds in broadband continuous noises, critical ratios were computed. Fletcher critical bands were narrower than either 15 or 111 of an octave at the low frequencies of the call (<2 kHz), depending on which frequency the animal cued on. From the masked hearing thresholds in intermittent noises, the audible signal duration at detection threshold was computed. The intermittent noises differed in gap length, gap number, and masking, but the total audible signal duration at threshold was the same: 660 ms. This observation supports a multiple-looks model. The two amplitude modulated noises exhibited weaker masking than the unmodulated noises hinting at a comodulation masking release.
本文研究了自然噪声和人为噪声对白鲸复杂发声的掩蔽作用。该叫声由六个150毫秒的脉冲组成，频谱峰值在800赫兹至8千赫兹之间。将叫声与检测阈值下的噪声频谱及声谱图进行比较，发现动物在阈值时并未听到整个叫声。它仅在频率和时间上听到了叫声的部分内容。根据宽带连续噪声中的掩蔽听力阈值，计算出了临界比率。在叫声的低频部分（<2千赫兹），弗莱彻临界带宽比一个八度的15分之一或111分之一更窄，这取决于动物所关注的频率。根据间歇噪声中的掩蔽听力阈值，计算出了检测阈值时的可听信号持续时间。间歇噪声在间隙长度、间隙数量和掩蔽方面存在差异，但阈值时的总可听信号持续时间相同：660毫秒。这一观察结果支持了多注视模型。两种调幅噪声的掩蔽作用比未调制噪声弱，这暗示了共调制掩蔽释放。
