Department of Ecology, Evolution and Behavior, University of Minnesota, Twin Cities, 100 Ecology, 1987 Upper Buford Circle, St. Paul, MN 55108, USA.
Hear Res. 2012 Mar;285(1-2):86-97. doi: 10.1016/j.heares.2012.01.003. Epub 2012 Jan 8.
Humans and other animals often communicate acoustically in noisy social groups, in which the background noise generated by other individuals can mask signals of interest. When listening to speech in the presence of speech-like noise, humans experience a release from auditory masking when target and masker are spatially separated. We investigated spatial release from masking (SRM) in a free-field call recognition task in Cope's gray treefrog (Hyla chrysoscelis). In this species, reproduction requires that females successfully detect, recognize, and localize a conspecific male in the noisy social environment of a breeding chorus. Using no-choice phonotaxis assays, we measured females' signal recognition thresholds in response to a target signal (an advertisement call) in the presence and absence of chorus-shaped noise. Females experienced about 3 dB of masking release, compared with a co-localized condition, when the masker was displaced 90° in azimuth from the target. The magnitude of masking release was independent of the spectral composition of the target (carriers of 1.3 kHz, 2.6 kHz, or both). Our results indicate that frogs experience a modest degree of spatial unmasking when performing a call recognition task in the free-field, and suggest that variation in signal spectral content has small effects on both source identification and spatial unmasking. We discuss these results in the context of spatial unmasking in vertebrates and call recognition in frogs.
人类和其他动物在嘈杂的社会群体中经常通过声学方式进行交流，在这些群体中，其他个体产生的背景噪声会掩盖感兴趣的信号。当在存在类似语音噪声的情况下聆听语音时，当目标和掩蔽者在空间上分开时，人类会体验到听觉掩蔽的释放。我们在 Cope 的灰树蛙（Hyla chrysoscelis）的自由场叫声识别任务中研究了空间掩蔽释放（SRM）。在这个物种中，繁殖需要雌性在繁殖合唱的嘈杂社会环境中成功地检测、识别和定位同种雄性。使用无选择的语音定向测定法，我们测量了雌性在存在和不存在合唱噪声的情况下对目标信号（广告叫声）的信号识别阈值。与共定位条件相比，当掩蔽器在方位上从目标移开 90°时，雌性经历了约 3 dB 的掩蔽释放。掩蔽释放的幅度与目标的光谱组成无关（载波为 1.3 kHz、2.6 kHz 或两者兼有）。我们的结果表明，青蛙在自由场执行叫声识别任务时会经历适度的空间去掩蔽，这表明信号光谱内容的变化对声源识别和空间去掩蔽的影响都很小。我们在脊椎动物的空间去掩蔽和青蛙的叫声识别的背景下讨论了这些结果。
