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- Measurements of humpback whale song sound levels received by a calf in association with a singer
- Male humpback whales produce loud "songs" on the wintering grounds and some sing while escorting mother-calf pairs, exposing them to near-continuous sounds at close proximity. An Acousonde acoustic and movement recording tag deployed on a calf off Maui, Hawaii captured sounds produced by a singing male escort. Root-mean-square received levels ranged from 126 to 158 dB re 1 μPa. These levels represent rare direct measurements of sound to which a newly born humpback calf may be naturally exposed by a conspecific, and may provide a basis for informed decisions regarding anthropogenic sound levels projected near calves., Article
- Chen, Pack, Au, Stimpert
- Underwater sound measurements of a high-speed jet-propelled marine craft: Implications for large whales
- Radiated noise from a high-speed jet-propelled watercraft (the M/V Alakai, 1,646 tons, length 117 m) was measured at hydrophone depths of 3, 6, and 10 m while the ship passed by at speeds of 6.1733 m/sec (12 knots), 12.3467 m/sec (24 knots), and 19.0344 m/sec (37 knots). Noise spectra were similar for all speeds and hydrophone depths. Spectra peaked below 100 Hz and dropped off continuously at higher frequencies. Calculated source level noise was 10 to 20 dB lower than noise from propeller-driven ships and much lower than for ships of similar speed. Although exposure to noise radiating from the M/V Alakai over short time periods is unlikely to cause hearing damage to whales, the combination of low radiated noise levels and high transit speeds leads to a shorter closing time (defined as time between when source level of the ship at a stationary receiver is greater than ambient noise and time that a ship traveling directly toward the receiver arrives at its location) between ship and whale. Compared with other types of ships traveling at similar speeds, closing time for the Alakai ranges from 20 sec shorter (at 6.17333 m/sec [12 knots]) to 22 min shorter (at 19.0344 m/sec [37 knots]). Shortest closing time for the Alakai is 89.1 sec at a speed of 6.17333 m/sec (12 knots). Shortened closing time might reduce successful detection and avoidance of high-speed jet-propelled ships by whales, and increased speed shortens the time during which whales have the opportunity to respond to this detection.
- Rudd, Richlen, Stimpert, Au