Auditory Perception in Noisy 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 perceiving 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 comparatively less attention toward understanding how animals solve biological problems that are in many ways similar to the human cocktail party problem. Among the best known examples of "animal cocktail parties" are choruses of frogs and insects, the songbird dawn chorus, and large groups of colonial birds and mammals. Understanding the sensory solutions to the cocktail party problem has been a goal of research on human hearing and speech perception for several decades.

A major aspect of ongoing work in the lab is a project currently funded by the National Institute on Deafness and Other Communication Disorders 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. You can check out a TV commercial HERE. You can find a shorter version on YouTube by clicking HERE.

Our long-term goal is to understand the neural mechanisms for sound source segregation in noisy environments. We are currently using behavioral methods to investigate how the auditory systems of female gray 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. 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 the proposed research is that by gaining a better understanding of the bottom-up mechanisms for sound source segregation in frogs and other animals, we will contribute to the body of knowledge that could lead to the development of biologically-inspired technologies that could help the hearing impaired.

We have also conducted work on this topic in collaboration with Prof. Dr. Georg Klump at the Carl von Ossietzky University in Oldenburg, Germany. In that work, we were using the European starling as a model system for understanding how the brain processes acoustic signals in the presence of noise or other interfering sounds. Aspects of this work continue in collaboration wtih the Klump lab and wtih Dr. Christophe Micheyl in the UMN Auditory Percetion and Cognition Lab headed by Dr. Andrew Oxenham in the Department of Psychology.

Related Publications:

• Bee MA and Schwartz JJ (2009) Behavioral measures of signal recognition thresholds in frogs in the presence and absence of chorus-shaped noise. Journal of the Acoustical Society of America, in press. (Uncorrected Proofs)

• Bee MA and Micheyl C (2008) The cocktail party problem: What is it? How can it be solved? And why should animal behaviorists study it? Journal of Comparative Psychology, 122, 235-251. PDF

• Bee MA (2008) Parallel female preferences for call duration in a diploid ancestor of an allotetraploid treefrog. Animal Behaviour, 76, 845-853. PDF

• Bee MA and Riemersma KK (2008) Does common spatial origin promote the auditory grouping of temporally separated signal elements in grey treefrogs? Animal Behaviour, 76, 831-843. PDF

• Bee MA (2008) Finding a mate at a cocktail party: Spatial release from masking improves acoustic mate recognition in grey treefrogs. Animal Behaviour, 75, 1781-1791. PDF

• Bee MA and Swanson EM (2007) Auditory masking of anuran advertisement calls by road traffic noise. Animal Behaviour, 74, 1765-1776. PDF

• Bee MA ( 2007) Sound source segregation in the grey treefrog: Spatial release from masking by the sound of a chorus. Animal Behaviour, 74, 549-558. PDF

• Bee MA , Buschermöhle M, and Klump GM ( 2007) Detecting modulated signals in modulated noise: II. Neural thresholds from the songbird auditory forebrain. European Journal of Neuroscience, 26, 1979-1994. PDF

• Buschermöhle M, Feudel U, Klump GM, Bee MA , and Freund J (2006) Signal detection enhanced by comodulated noise. Fluctuation and Noise Letters , 6, 339-348. PDF

• Bee MA and Klump GM (2005) Auditory stream segregation in the songbird forebrain: Effects of time intervals on responses to interleaved tone sequences. Brain, Behavior and Evolution, 66, 197-214. PDF

• Bee MA and Klump GM (2004) Primitive auditory stream segregation: A neurophysiological study in the songbird forebrain. Journal of Neurophysiology, 92, 1088-1104. PDF