Abstract
A psychoacoustic behavioral technique was used to determine the critical ratios (CRs) of two harbor porpoises for tonal signals with frequencies between 0.315 and 150 kHz, in random Gaussian white noise. The masked 50% detection hearing thresholds were measured using a "go/no-go" response paradigm and an up-down staircase psychometric method. CRs were determined at one masking noise level for each test frequency and were similar in both animals. For signals between 0.315 and 4 kHz, the CRs were relatively constant at around 18 dB. Between 4 and 150 kHz the CR increased gradually from 18 to 39 dB (∼3.3 dB/octave). Generally harbor porpoises can detect tonal signals in Gaussian white noise slightly better than most odontocetes tested so far. By combining the mean CRs found in the present study with the spectrum level of the background noise levels at sea, the basic audiogram, and the directivity index, the detection threshold levels of harbor porpoises for tonal signals in various sea states can be calculated.
| Original language | English |
|---|---|
| Pages (from-to) | 1588-1597 |
| Number of pages | 10 |
| Journal | Journal of the Acoustical Society of America |
| Volume | 126 |
| Issue number | 3 |
| DOIs | |
| Publication status | Published - 2009 |
Bibliographical note
Funding Information:The authors thank students Remona Kerssies, Krista Krijger, Tess van der Drift, Alejandra Vargas, Janna Loot, Eline Berrevoets, and Niek Boonman; and volunteers Menno van den Berg, Jesse Dijkhuizen, Cathy Philipse, Saskia Roose, Joke de Lange, Wijnand de Wolf, Mary Mullaney, Sandra Wisse, and Jaya de Jonge for their help with training and data collection. The authors thank Rob Triesscheijn for making the figures, Bert Meijering, director of sea bait farm Topsy Baits, for providing space for SEAMARCO’s Research Institute, and Hein Hermans for technical support at the Research Institute. The authors thank Willem Verboom (JunoBioacoustics) and Erwin Jansen (TNO-Delft) for the acoustic calibration measurements and TNO-Delft for providing the J-11 transducer for this study. The authors thank Dick de Haan (Wageningen IMARES) for technical assistance and Veenhuis Medical Audio (Marco Veenhuis and Herman Walstra) for donating and modifying the audiometer. The authors thank Teun Tollenaar (T.T. Electronics, Harderwijk) and Menno van den Berg for the construction of the sound generator used during the training phase of the project, and Arie Smink for the construction of the mixer. The authors thank the Royal Netherlands Navy for lending the IJkmonitor for the study, and Hans Heiligenberg and Raymond van Elst (Royal Netherlands Navy) for their help in providing the RANA LF transducer. They also thank Nancy Jennings (dotmoth.co.uk, Bristol, UK) and two anonymous reviewers for their valuable constructive comments on the design of the study and on this manuscript. Funding for this project was obtained from The Netherlands Ministry of Defense (Contract No. WO Bruinvissen 235-06-0003-01). The authors thank Erik van Arkel, Vincent Gales, Ronald de Rooij (DRMV, Netherlands Ministry of Defense), and René Dekeling and Frans Jansen (Royal Netherlands Navy) for their guidance during the project. The training and testing of the porpoises were conducted under authorization of the Netherlands Ministry of Agriculture, Nature and Food Quality, Department of Nature Management, with Endangered Species Permit No. FF/75A/2005/047. The authors thank Seppe Raaphorst and Jan van Spaandonk (Ministry of Agriculture, Nature and Food Quality of the Netherlands) for their assistance in making the harbor porpoises available for this project.