Composite critical ratio functions for odontocete cetaceans

Area of Science:

• Marine biology
• Bioacoustics
• Auditory science

Background:

• Critical ratios (CRs) are vital for understanding auditory detection thresholds in noise.
• Existing CR data for cetaceans are limited, especially at lower frequencies affected by human-generated noise.
• A systematic method for predicting CRs, like a composite frequency-dependent function, is lacking.

Purpose of the Study:

• To measure CRs in bottlenose dolphins (Tursiops truncatus).
• To develop and estimate composite CR functions for predicting auditory masking.
• To address data gaps in cetacean auditory science, particularly for low-frequency noise impacts.

Main Methods:

• Auditory evoked potential (AEP) measurements were used to determine detection thresholds.
• Two bottlenose dolphins were tested across a range of tonal signal frequencies and noise levels.
• Statistical modeling was employed to derive composite frequency-dependent CR functions.

Main Results:

• Measured CRs for bottlenose dolphins, providing new empirical data.
• Developed composite CR functions that model frequency-dependent auditory masking.
• Demonstrated the utility of composite models for extrapolating CRs across a broader frequency spectrum.

Conclusions:

• The developed composite CR functions offer a systematic approach to predict auditory masking in bottlenose dolphins.
• These models can be applied to assess the impact of anthropogenic noise on cetacean hearing.
• The study contributes valuable data to marine mammal bioacoustics and conservation efforts.