title: Effect of level, duration, and inter-pulse interval of 1-2 kHz sonar signal exposures on harbor porpoise hearing.
abstract: Safety criteria for underwater low-frequency active sonar sounds produced during naval exercises are needed to protect harbor porpoise hearing. As a first step toward defining criteria, a porpoise was exposed to sequences consisting of series of 1-s, 1-2 kHz sonar down-sweeps without harmonics (as fatiguing noise) at various combinations of average received sound pressure levels (SPLs; 144-179 dB re 1 μPa), exposure durations (1.9-240 min), and duty cycles (5%-100%). Hearing thresholds were determined for a narrow-band frequency-swept sine wave centered at 1.5 kHz before exposure to the fatiguing noise, and at 1-4, 4-8, 8-12, 48, 96, 144, and 1400 min after exposure, to quantify temporary threshold shifts (TTSs) and recovery of hearing. Results show that the inter-pulse interval of the fatiguing noise is an important parameter in determining the magnitude of noise-induced TTS. For the reported range of exposure combinations (duration and SPL), the energy of the exposure (i.e., cumulative sound exposure level; SELcum) can be used to predict the induced TTS, if the inter-pulse interval is known. Exposures with equal SELcum but with different inter-pulse intervals do not result in the same induced TTS.
authors.affiliation: Sea Mammal Research Company, Julianalaan 46, 3843 CC Harderwijk, The Netherlands.
authors.forename: Ronald A
authors.initials: RA
authors.lastname: Kastelein
authors.affiliation: Sea Mammal Research Company, Julianalaan 46, 3843 CC Harderwijk, The Netherlands.
authors.forename: Lean
authors.initials: L
authors.lastname: Hoek
authors.affiliation: Sea Mammal Research Company, Julianalaan 46, 3843 CC Harderwijk, The Netherlands.
authors.forename: Robin
authors.initials: R
authors.lastname: Gransier
authors.affiliation: Sea Mammal Research Company, Julianalaan 46, 3843 CC Harderwijk, The Netherlands.
authors.forename: Martijn
authors.initials: M
authors.lastname: Rambags
authors.affiliation: Sea Mammal Research Company, Julianalaan 46, 3843 CC Harderwijk, The Netherlands.
authors.forename: Naomi
authors.initials: N
authors.lastname: Claeys
mesh_terms: D000161:Acoustic Stimulation / Q000379:methods*; D000162:Acoustics; D000818:Animals; D001301:Audiometry, Pure-Tone; D001305:Auditory Fatigue; D001309:Auditory Threshold; D004781:Environmental Exposure / Q000009:adverse effects; D006309:Hearing; D008297:Male; D009622:Noise / Q000009:adverse effects*; D050741:Phocoena / Q000502:physiology / Q000523:psychology*; D011312:Pressure; D020127:Recovery of Function; D018570:Risk Assessment; D013018:Sound Spectrography; D013550:Swimming; D013997:Time Factors