in Helsinki Peter Sigray Coordinator of the BIAS-project Helsinki - PowerPoint PPT Presentation

HELCOM-BIAS Workshop in Helsinki Peter Sigray Coordinator of the BIAS-project Helsinki November 2014

Underwater Acoustics and Sources Underwater Acoustics • Source generating sound • A medium wherein the sound can propagate • A reciever that is affected There are natural occurring sound and human-made sound

Natural biological sound From DOSIT Discovery of the sound in the sea; http://www.dosits.org/

Natural abiotic ambient sound From DOSIT Discovery of the sound in the sea; http://www.dosits.org/

Anthropogenic sound From DOSIT Discovery of the sound in the sea; http://www.dosits.org/

So Sour urces ces

Summary of sources Natural biological sound The anthropogenic sound Natural non-biological sound levels are rising. Anthropogenic Sound McDonald et al., 2006

Propagation of sound in water Wave propagation depends on several factors • Sea surface • Sea bed • Sound velocity • Absorption Sound velocity of the deep oceans

Underwater sound from the perspective of a fish Sound consists of both: - Sound pressure variations (swim bladder involved) - Particle motion – hearing organ (otholits) - Two main categorize of sound: Impulsive and continuous Both co-exists! Pressure Particle motion http://www.acs.psu.edu/drussell /demos/waves/wavemotion.html

Entities for Sound p r  m s 1 / T  p p pp in [Pa] ( t T ) 2 d t REMEMBER THIS p pp = max(p(t))-min(p(t)) p rms in [Pa] SPL = Sound Pressure Level in dB re. 1µPa (A explosion close by will damage your hearing) SEL = Sound Exposure Level in [dB re 1 µPa²s] (Loud sound in a bar will slowly damage your hearing)

Propagation of sound in shallow water Summer Winter 50 Hz: dashed 500 Hz: solid Summer & Autumn Winter: black Winter& Spring Summer: blue

Ambient noise in Öresund Sound pressure dB re 1 µPa

Ambient noise in Öresund 600 m from shipping lane

Ambient noise 600 m from shipping lane Dist. tol Measured Measured Esitmated intesity Esitmated Ship name Fartygstyp MMSI Speed hydrophon intesity intesity @ 1 m intesity @ 1 m 20-4000 number (knots) (m) (Hz) 123-132 (Hz) 20-4000 (Hz) 123-132 (Hz) Lillgrund Serviceboat 219010942 9 30 124 89 149 114 Finnpartner Passenger ferry 266262000 12 550 133 102 180 149 Viscaria Tanker 258897000 10 630 121 74 169 122 Finneagle Passenger ferry 265740000 11 620 129 99 176 146

Basic physics of underwater acoustics Measured in dB relative to 1µPa  3 dB is a doubling of pressure, 6 dB ten times larger Sound consists of both pressure variations and particle motion Echoes (reverberation) in shallow water acoustics are common – long reverberation The speed of sound in water is 1500 m/s, in air 350 m/s, localization is done differently underwater The environmental influence is large especially the thermocline and the halocline in the Baltic Sea Distinguish between impulsive and continuous sound

Cumulative effects Sound pressure dB re 1 µPa 500 turbines 80 turbines Ambient Source level of wind turbine 136 dB re 1μPa for a 150 Hz tone Cumulative effects has to be estimated

The MSFD Descriptor 11

Indicator 11.1.1: There are evidences that species react to loud sound sources: Member States have to have a book keeping system to avoid exposures that will harm the marine environment Indicator 11.2.1: The trend seems to be increasing in many places: The Member States have to monitor the noise to establish what the trend is

Sources to be included in the Registry • Airgun: SLz-p > 209 dB re 1 μPa m • Low-mid frequency sonar: SL > 176 dB re 1 μPa m • Low-mid freq. acoustic deterrent: SL > 176 dB re 1 μPa m • Generic non-impulsive sound source: SL > 176 dB re 1 μPa m3 Explosions: mTNTeq > 8 g • • Generic impulsive sound source SLE > 186 dB re 1 μPa² m² s