Research...

 

HEARING in Noisy Social Environments (The Frog's "Cocktail Party Problem")

Animals often use acoustic signals to communicate in groups or social aggregations in which multiple individuals signal within a receiver’s hearing range. Consequently, receivers face challenges related to acoustic interference and auditory masking that are not unlike the human cocktail party problem, which refers to the well-known difficulty we have understanding speech in noisy social settings, such as a cocktail party or a crowded cafeteria. Despite a general interest in acoustic signaling in groups, however, animal behaviorists have devoted little attention toward understanding how animals solve their own cocktail-party-like problems. Among the best known examples of "animal cocktail parties" are choruses of frogs.

Our long-term goal is to understand the neural mechanisms for sound source perception in noisy environments. We are currently using behavioral, biomechanical, and neurophysiological methods to investigate how the auditory systems of North American treefrogs exploit spectral, temporal, and spatial cues to perceive mating calls in noisy choruses. Typical frog calls have amplitudes of 80-90 dB SPL (at 1 m), and breeding choruses commonly range in size from dozens to hundreds of calling males, usually of multiple species. In order to reproduce, female frogs must detect, recognize, localize, and discriminate among the calls of individual males in the chorus. Our central hypothesis is that frogs possess low-level, “bottom-up” mechanisms that segregate vocal communication signals from overlapping signals and from the general din of a noisy social environment. This hypothesis is based on preliminary data and on the fact that frogs do not rely on higher-level cognitive processing for communication, and yet they must solve a biological equivalent of the human cocktail party problem. The rationale for our research is that by gaining a better understanding of the bottom-up mechanisms for sound source perception in frogs and other animals, we will contribute to the body of knowledge that could lead to the development of improved biologically-inspired technologies to help the hearing impaired.

Major aspects of ongoing work in the lab involve projects currently funded by the National Institute on Deafness and Other Communication Disorders and the National Science Foundation that investigates how the frog auditory system perceives vocal communication signals (male mating calls) in noisy social environments (breeding choruses). This work has been featured in the University of Minnesota's Drive to Discover campaign and is highlighted in this short YouTube video.

 

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