Correction: Separating underwater ambient noise from flow noise recorded on stereo acoustic tags attached to marine mammals

Ocean noise varies spatially and temporally and is driven by natural and anthropogenic processes. Increased ambient noise levels can cause signal masking and communication impairment, affecting fitness and recruitment success. However, the effects of increasing ambient noise levels on marine species, such as marine mammals that primarily rely on sound for communication, are not well understood. We investigated the effects of concurrent ambient noise levels on social whistle calls produced by bottlenose dolphins ( Tursiops truncatus ) in the western North Atlantic. Elevated ambient noise levels were mainly caused by ship noise. Increases in ship noise, both within and below the dolphins' call bandwidth, resulted in higher dolphin whistle frequencies and a reduction in whistle contour complexity, an acoustic feature associated with individual identification. Consequently, the noise-induced simplification of dolphin whistles may reduce the information content in these acoustic signals and decrease effective communication, parent–offspring proximity or group cohesion.

Download Full-text

Two new grey whale call types detected on bioacoustic tags

Journal of the Marine Biological Association of the United Kingdom ◽

10.1017/s0025315416001697 ◽

2016 ◽

Vol 98 (5) ◽

pp. 1169-1175 ◽

Cited By ~ 3

Author(s):

Anaid López-Urbán ◽

Aaron Thode ◽

Carmen Bazúa Durán ◽

Jorge UrbáN-R ◽

Steven Swartz

Keyword(s):

Spectral Analysis ◽

Mechanical Vibration ◽

Biosphere Reserve ◽

Flow Noise ◽

Grey Whale ◽

Acoustic Tags

Between 2008 and 2010, 27 acoustic tags were applied to various age and reproductive classes of grey whales in Laguna San Ignacio, Mexico, a part of the Biosphere Reserve ‘El Vizcaino’. Besides previously described S1 and S3 calls, two additional calls were identified: the impulsive S8 call and the slightly frequency-modulated S9 call. These two additional S8 and S9 calls are by far the most common grey whale sounds detected on tags, even though contemporary bottom-mounted acoustic recordings also collected from the lagoon in 2008 yielded no S8 or S9 calls. The new S8 and old S3 calls display similar spectral maxima, even though the S3 is a frequency-modulated harmonic call and the S8 is a broadband impulsive call. This spectral analysis provides evidence that these new call types are not artefacts arising from mechanical vibration or flow noise.

Download Full-text

Noise Model Analysis and Estimation of Effect due to Wind Driven Ambient Noise in Shallow Water

International Journal of Oceanography ◽

10.1155/2011/950838 ◽

2011 ◽

Vol 2011 ◽

pp. 1-4 ◽

Cited By ~ 3

Author(s):

S. Sakthivel Murugan ◽

V. Natarajan ◽

R. Rajesh Kumar

Keyword(s):

Wind Speed ◽

Marine Mammals ◽

Ambient Noise ◽

Signal Transmission ◽

Acoustic Signals ◽

Noise Spectrum ◽

Noise Model ◽

Frequency Range ◽

Entire Frequency Range ◽

Wind Speeds

Signal transmission in ocean using water as a channel is a challenging process due to attenuation, spreading, reverberation, absorption, and so forth, apart from the contribution of acoustic signals due to ambient noises. Ambient noises in sea are of two types: manmade (shipping, aircraft over the sea, motor on boat, etc.) and natural (rain, wind, seismic, etc.), apart from marine mammals and phytoplanktons. Since wind exists in all places and at all time: its effect plays a major role. Hence, in this paper, we concentrate on estimating the effects of wind. Seven sets of data with various wind speeds ranging from 2.11 m/s to 6.57 m/s were used. The analysis is performed for frequencies ranging from 100 Hz to 8 kHz. It is found that a linear relationship between noise spectrum and wind speed exists for the entire frequency range. Further, we developed a noise model for analyzing the noise level. The results of the empirical data are found to fit with results obtained with the aid of noise model.

Download Full-text