Spatial and Temporal Variability of Ambient Underwater Sound in the Baltic Sea

Area of Science:

• Marine acoustics
• Environmental science
• Oceanography

Background:

• Anthropogenic underwater sound poses a chronic threat to marine species.
• Limited research exists on the spatial and temporal variability of ambient sound and its influencing factors.

Purpose of the Study:

• To analyze large-scale, long-term underwater sound monitoring data from the Baltic Sea.
• To investigate the variability of ambient sound levels influenced by natural conditions and ship traffic.

Main Methods:

• Conducted underwater sound monitoring across 36 Baltic Sea locations throughout 2014.
• Calculated and analyzed sound pressure levels in 63 Hz, 125 Hz, and 2 kHz one-third octave bands.
• Examined annual and monthly median levels and probability density functions.

Main Results:

• Significant spatial variations in sound pressure levels were observed, with annual medians differing by nearly 50 dB at 63 Hz.
• Monthly median differences reached up to 15 dB at 63 Hz.
• Maritime traffic was found to elevate ambient sound levels in many Baltic Sea areas.

Conclusions:

• Underwater ambient sound in the Baltic Sea exhibits substantial spatial and temporal variability.
• Ship traffic is a significant contributor to elevated sound levels.
• Further research is needed to understand the full impact on marine ecosystems.