Warnecke Michaela, Bates Mary E, Flores Victoria, Simmons James A
J Acoust Soc Am. 2014 May;135(5):3077-85. doi: 10.1121/1.4869483.
Big brown bats (Eptesicus fuscus) use biosonar to navigate and locate objects in their surroundings. During natural foraging, they often encounter echoes returned by a target of interest located to the front while other, often stronger, clutter echoes are returned from objects, such as vegetation, located to the sides or above. Nevertheless, bats behave as if they do not suffer interference from this clutter. Using a two-choice delay discrimination procedure, bats were tested for the masking effectiveness of clutter echoes on target echoes when the target echoes were delivered from the bat's front while clutter echoes were delivered from 90° overhead, a direction of lowpass filtering by the external ears. When clutter echoes are presented from the front at the same delay as target echoes, detection performance declines and clutter masking occurs. When the clutter echoes are presented at the same delay but from overhead, discrimination performance is unaffected and no masking occurs. Thus there is masking release for simultaneous off-axis lowpass clutter compared to masking by simultaneous clutter from the front. The bat's performance for simultaneous target and clutter echoes indicates a new role for the mechanism that separates overlapping echoes by decomposing the bat's auditory time-frequency representation.
大棕蝠（棕蝠）利用生物声纳在周围环境中导航和定位物体。在自然觅食过程中，它们经常会遇到来自前方感兴趣目标返回的回声，而其他通常更强的杂波回声则来自位于侧面或上方的物体，如植被。然而，蝙蝠的行为表现就好像它们没有受到这种杂波的干扰。采用二选一延迟辨别程序，当目标回声从蝙蝠前方发出而杂波回声从头顶90°发出（这是外耳进行低通滤波的方向）时，测试了蝙蝠对杂波回声对目标回声的掩蔽效果。当杂波回声与目标回声以相同延迟从前方呈现时，检测性能下降，出现杂波掩蔽。当杂波回声以相同延迟但从头顶呈现时，辨别性能不受影响，也不发生掩蔽。因此，与来自前方的同时杂波掩蔽相比，同时离轴低通杂波存在掩蔽解除。蝙蝠对同时出现的目标和杂波回声的表现表明，通过分解蝙蝠的听觉时频表征来分离重叠回声的机制有了新作用。
