Inherent Directionality Determines Spatial Release from Masking at the Tympanum in a Vertebrate with Internally Coupled Ears

Michael S. Caldwell, Norman Lee, Mark A. Bee

Research output: Contribution to journalArticlepeer-review

3 Scopus citations

Abstract

In contrast to humans and other mammals, many animals have internally coupled ears that function as inherently directional pressure-gradient receivers. Two important but unanswered questions are to what extent and how do animals with such ears exploit spatial cues in the perceptual analysis of noisy and complex acoustic scenes? This study of Cope’s gray treefrog (Hyla chrysoscelis) investigated how the inherent directionality of internally coupled ears contributes to spatial release from masking. We used laser vibrometry and signal detection theory to determine the threshold signal-to-noise ratio at which the tympanum’s response to vocalizations could be reliably detected in noise. Thresholds were determined as a function of signal location, noise location, and signal-noise separation. Vocalizations were broadcast from one of three azimuthal locations: frontal (0 °), to the right (+90 °), and to the left (−90 °). Masking noise was broadcast from each of 12 azimuthal angles around the frog (0 to 330 °, 30 ° separation). Variation in the position of the noise source resulted in, on average, 4 dB of spatial release from masking relative to co-located conditions. However, detection thresholds could be up to 9 dB lower in the “best ear for listening” compared to the other ear. The pattern and magnitude of spatial release from masking were well predicted by the tympanum’s inherent directionality. We discuss how the magnitude of masking release observed in the tympanum’s response to spatially separated signals and noise relates to that observed in previous behavioral and neurophysiological studies of frog hearing and communication.

Original languageEnglish (US)
Pages (from-to)259-270
Number of pages12
JournalJARO - Journal of the Association for Research in Otolaryngology
Volume17
Issue number4
DOIs
StatePublished - Aug 1 2016

Bibliographical note

Funding Information:
We thank Katrina Schrode for providing code used in data analysis, Jessica Ward for logistical support, Shelby Seckora, Nathan Buerkle, and Sam Levin for assistance in data collection, and three anonymous reviewers for helpful feedback on earlier drafts. This research was supported by a grant from the National Institute on Deafness and Other Communication Disorders (R01 DC009582).

Funding Information:
We thank Katrina Schrode for providing code used in data analysis, Jessica Ward for logistical support, Shelby Seckora, Nathan Buerkle, and Sam Levin for assistance in data collection, and three anonymous reviewers for helpful feedback on earlier drafts. This research was supported by a grant from the National Institute on Deafness and Other Communication Disorders (R01 DC009582).

Publisher Copyright:
© 2016, Association for Research in Otolaryngology.

Keywords

  • acoustic communication
  • cocktail party problem
  • pressure-gradient receiver
  • sound source segregation
  • spatial unmasking
  • vocal communication

Fingerprint

Dive into the research topics of 'Inherent Directionality Determines Spatial Release from Masking at the Tympanum in a Vertebrate with Internally Coupled Ears'. Together they form a unique fingerprint.

Cite this