On the Relationship Between Environmental Noise, Critical Ratios, and Comodulation Masking Release in the Bottlenose Dolphin (Tursiops truncatus)

  • Brian K. Branstetter
  • Jennifer S. Trickey
  • James J. Finneran
Part of the Advances in Experimental Medicine and Biology book series (AEMB, volume 730)


When one sound interferes with the ability to detect another sound, masking occurs. The potential negative impacts of masking include the inability to effectively communicate, navigate, and forage. Due to the difficulty in acquiring, maintaining, and training marine mammals to participate in psychophysical testing, only a limited number of masking studies have been conducted. Most of these are critical-ratio and critical-band measurements. A primary finding of these studies is that masking typically occurs only when the frequency of the signal and masker are similar (Fletcher 1940). For example, critical-band and notched-noise experiments using white-noise maskers (i.e., the instantaneous amplitude is sampled from a Gaussian distribution and the frequency spectrum is flat) suggest that only noise frequencies within a narrow band centered on a tonal signal contribute to the ­masking of the signal (Au and Moore 1990; Finneran et al. 2002; Southall et al. 2003).


  1. Au WWL, Moore PWB (1990) Critical ratio and critical bandwidth for the Atlantic bottlenose dolphin. J Acoust Soc Am 88:1635–1638.PubMedCrossRefGoogle Scholar
  2. Branstetter BK, Finneran JJ (2008) Comodulation masking release in bottlenose dolphins (Tursiops truncatus). J Acoust Soc Am 124:625–633.PubMedCrossRefGoogle Scholar
  3. Erbe C (2008) Critical ratios of beluga whales (Delphinapterus leucas) and masked signal duration. J Acoust Soc Am 124:2216–2223.PubMedCrossRefGoogle Scholar
  4. Finneran JJ, Schlundt CE, Carder DA, Ridgway SH (2002) Auditory filter shapes for the bottlenose dolphin (Tursiops truncatus) and the white whale (Delphinapterus leucas) derived with notched noise. J Acoust Soc Am 112:322–328.PubMedCrossRefGoogle Scholar
  5. Fletcher H (1940) Auditory patterns. Rev Mod Phys 12:47–65.CrossRefGoogle Scholar
  6. Southall BL, Schusterman RJ, Kastak D (2003) Auditory masking in three pinnipeds: Aerial critical ratios and direct critical bandwidth measurements. J Acoust Soc Am 114:1660–1666.PubMedCrossRefGoogle Scholar

Copyright information

© Springer Science+Business Media, LLC 2012

Authors and Affiliations

  • Brian K. Branstetter
    • 1
  • Jennifer S. Trickey
    • 2
  • James J. Finneran
    • 3
  1. 1.National Marine Mammal FoundationSan DiegoUSA
  2. 2.G2 Software Systems Inc.San DiegoUSA
  3. 3.US Navy Marine Mammal ProgramSpace and Naval Warfare Systems Center PacificSan DiegoUSA

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