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Dolphins adjust species-specific frequency parameters to compensate for increasing background noise.

Papale E, Gamba M, Perez-Gil M, Martin VM, Giacoma C - PLoS ONE (2015)

Bottom Line: In this study we explored the effects of anthropogenic and natural noise on the acoustic properties of a dolphin communication signal, the whistle.Results show that dolphins increase the whistles' frequency parameters with lower variability in the presence of anthropogenic noise, and increase the end frequency of their whistles when confronted with increasing natural noise.This study provides the first evidence that the synergy among SPLs has a role in shaping the whistles' structure of these three species, with respect to both natural and anthropogenic noise.

View Article: PubMed Central - PubMed

Affiliation: University of Torino, Life Sciences and Systems Biology Department, Torino, Italy.

ABSTRACT
An increase in ocean noise levels could interfere with acoustic communication of marine mammals. In this study we explored the effects of anthropogenic and natural noise on the acoustic properties of a dolphin communication signal, the whistle. A towed array with four elements was used to record environmental background noise and whistles of short-beaked common-, Atlantic spotted- and striped-dolphins in the Canaries archipelago. Four frequency parameters were measured from each whistle, while Sound Pressure Levels (SPL) of the background noise were measured at the central frequencies of seven one-third octave bands, from 5 to 20 kHz. Results show that dolphins increase the whistles' frequency parameters with lower variability in the presence of anthropogenic noise, and increase the end frequency of their whistles when confronted with increasing natural noise. This study provides the first evidence that the synergy among SPLs has a role in shaping the whistles' structure of these three species, with respect to both natural and anthropogenic noise.

No MeSH data available.


Sound Pressure Levels in dB (ref. 1μPa ± 1dB) in the communication frequency bands from 1 to 22 kHz.We considered for each sighting a recording, of maximum 10 sec, collected throughout the period before or after a sequence of whistles. Sound Pressure Levels (SPLs) of the central frequencies of each one-third-octave band were extracted using PRAAT [30]. The mean level of environmental background noise was analyzed in good weather conditions (0–1) (category A) and in the worst weather conditions (2–3) (category B) for which we were sure that no boats were present within one mile from the research vessel. We pooled in a third category all recordings with SPLs overcoming the ones collected in the worst weather conditions, assuming that the highest levels in mid-frequency bands could be attributed to cavitating propellers of passing vessels, audible over long distances (category C).
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pone.0121711.g003: Sound Pressure Levels in dB (ref. 1μPa ± 1dB) in the communication frequency bands from 1 to 22 kHz.We considered for each sighting a recording, of maximum 10 sec, collected throughout the period before or after a sequence of whistles. Sound Pressure Levels (SPLs) of the central frequencies of each one-third-octave band were extracted using PRAAT [30]. The mean level of environmental background noise was analyzed in good weather conditions (0–1) (category A) and in the worst weather conditions (2–3) (category B) for which we were sure that no boats were present within one mile from the research vessel. We pooled in a third category all recordings with SPLs overcoming the ones collected in the worst weather conditions, assuming that the highest levels in mid-frequency bands could be attributed to cavitating propellers of passing vessels, audible over long distances (category C).

Mentions: The environmental background noise recorded during dolphin sightings did not present impulsive events. SPLs measured in the 4.4 kHz—22.4 kHz range varied from a mean of 31.69 dB re 1 μ Pa in low noise for band 4.4–5.6 kHz to a mean of 110.90 dB re 1 μ Pa in high noise for band 8.9–11.2 kHz (Table 1). SPLs mean values of all 4.4 kHz—22.4 kHz bands of environmental noise recorded during standard survey conditions 0–1 (low noise category A) were lower than values obtained in conditions 2–3 (medium noise category B), and these last ones were lower than data obtained when additional sources of anthropogenic noise were present (high noise category C) (Fig. 3).


Dolphins adjust species-specific frequency parameters to compensate for increasing background noise.

Papale E, Gamba M, Perez-Gil M, Martin VM, Giacoma C - PLoS ONE (2015)

Sound Pressure Levels in dB (ref. 1μPa ± 1dB) in the communication frequency bands from 1 to 22 kHz.We considered for each sighting a recording, of maximum 10 sec, collected throughout the period before or after a sequence of whistles. Sound Pressure Levels (SPLs) of the central frequencies of each one-third-octave band were extracted using PRAAT [30]. The mean level of environmental background noise was analyzed in good weather conditions (0–1) (category A) and in the worst weather conditions (2–3) (category B) for which we were sure that no boats were present within one mile from the research vessel. We pooled in a third category all recordings with SPLs overcoming the ones collected in the worst weather conditions, assuming that the highest levels in mid-frequency bands could be attributed to cavitating propellers of passing vessels, audible over long distances (category C).
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4390328&req=5

pone.0121711.g003: Sound Pressure Levels in dB (ref. 1μPa ± 1dB) in the communication frequency bands from 1 to 22 kHz.We considered for each sighting a recording, of maximum 10 sec, collected throughout the period before or after a sequence of whistles. Sound Pressure Levels (SPLs) of the central frequencies of each one-third-octave band were extracted using PRAAT [30]. The mean level of environmental background noise was analyzed in good weather conditions (0–1) (category A) and in the worst weather conditions (2–3) (category B) for which we were sure that no boats were present within one mile from the research vessel. We pooled in a third category all recordings with SPLs overcoming the ones collected in the worst weather conditions, assuming that the highest levels in mid-frequency bands could be attributed to cavitating propellers of passing vessels, audible over long distances (category C).
Mentions: The environmental background noise recorded during dolphin sightings did not present impulsive events. SPLs measured in the 4.4 kHz—22.4 kHz range varied from a mean of 31.69 dB re 1 μ Pa in low noise for band 4.4–5.6 kHz to a mean of 110.90 dB re 1 μ Pa in high noise for band 8.9–11.2 kHz (Table 1). SPLs mean values of all 4.4 kHz—22.4 kHz bands of environmental noise recorded during standard survey conditions 0–1 (low noise category A) were lower than values obtained in conditions 2–3 (medium noise category B), and these last ones were lower than data obtained when additional sources of anthropogenic noise were present (high noise category C) (Fig. 3).

Bottom Line: In this study we explored the effects of anthropogenic and natural noise on the acoustic properties of a dolphin communication signal, the whistle.Results show that dolphins increase the whistles' frequency parameters with lower variability in the presence of anthropogenic noise, and increase the end frequency of their whistles when confronted with increasing natural noise.This study provides the first evidence that the synergy among SPLs has a role in shaping the whistles' structure of these three species, with respect to both natural and anthropogenic noise.

View Article: PubMed Central - PubMed

Affiliation: University of Torino, Life Sciences and Systems Biology Department, Torino, Italy.

ABSTRACT
An increase in ocean noise levels could interfere with acoustic communication of marine mammals. In this study we explored the effects of anthropogenic and natural noise on the acoustic properties of a dolphin communication signal, the whistle. A towed array with four elements was used to record environmental background noise and whistles of short-beaked common-, Atlantic spotted- and striped-dolphins in the Canaries archipelago. Four frequency parameters were measured from each whistle, while Sound Pressure Levels (SPL) of the background noise were measured at the central frequencies of seven one-third octave bands, from 5 to 20 kHz. Results show that dolphins increase the whistles' frequency parameters with lower variability in the presence of anthropogenic noise, and increase the end frequency of their whistles when confronted with increasing natural noise. This study provides the first evidence that the synergy among SPLs has a role in shaping the whistles' structure of these three species, with respect to both natural and anthropogenic noise.

No MeSH data available.