update on underwater noise and offshore wind farms. · update on underwater noise and offshore wind...
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Update on underwater noise and offshore wind farms.
Steve Parvin and Dr Jeremy NedwellSubacoustech Ltd
www.subacoustech.com
Aim of study
• To evaluate the subsea noise from construction and operation of wind farms and to rate it in terms of its potential for environmental effect
• “Noise Audit” approach - may include noise during construction, operation and decommissioning
Introduction
• Underwater sound measurement
• Species perceived sound level (dBht)
• Background noise
• Piling noise
• Operational noise
The underwater environment• Most underwater animals use sound
to navigate, communicate and explore their environment (fish, marine mammals, crustaceans, …)
• Man made underwater noise has great capacity to effect their environment
• How do we judge the significance of noise?
Underwater Source LevelsdB re 1 uPa @ 1 metre
Noise source
Source Level
Hear it!
Background noise 110-140
Vessel 170-190
Airgun array 190-240
Piling 170-270
Borehole blasting 220-260
Impact of Underwater sound
• Lethal: Peak levels greater than 240 dB re. 1 uPa (10‟s of metres)
• Injury: Peak levels greater than 220 dB re. 1 uPa (100‟s of metres).
• Behavioural response: Can extend to many 10‟s Kms.
Underwater hearing threshold
0
20
40
60
80
100
120
140
160
180
200
1 10 100 1000 10000 100000 1000000
Frequency (Hz)
So
un
d P
res
su
re L
ev
el
(dB
re
. 1
uP
a)
Fish
Underwater hearing threshold
0
20
40
60
80
100
120
140
160
180
200
1 10 100 1000 10000 100000 1000000
Frequency (Hz)
So
un
d P
ressu
re L
evel
(dB
re.
1 u
Pa
)
Marine mammals
Underwater hearing threshold
0
20
40
60
80
100
120
140
160
180
200
1 10 100 1000 10000 100000 1000000
Frequency (Hz)
So
un
d P
res
su
re L
ev
el(
dB
re
. 1
uP
a)
Human divers and swimmers
Underwater hearing thresholdPerceived loudness dBht
0
20
40
60
80
100
120
140
160
180
200
1 10 100 1000 10000 100000 1000000
Frequency (Hz)
So
un
d P
ressu
re L
evel(
dB
re. 1 u
Pa
)
Noise spectrum
Perceived „loudness‟ dBht
Effects of noiseLevel Comment Effects Human
equivalent
< 0 dBht Animal can‟t hear it
No reaction Soundproof room
0-90 dBht Increasingly loud
Reactions primarily cognitive
e.g. office, workshop
50 - 70 dBht
90-130 dBht Unbearably loud
Instinctive reaction (avoidance)
Roadhammer >100dBht
> 130 dBht Deafening Traumatic hearing damage
Gunfire near ear
Underwater noise survey
• UW sound recording 1 Hz to 175 kHz.
• Dynamic range up to 100 dB.
• Overall sound level (Pk-Pk).
• Species perceived sound level (dBht)
Mid HoyleChannel
WelshChannel
RHYL
Target Measurement Location
Wind Turbine
Not to Scale
N0
N1
N2
N3
S1
S2
S3
S4
S5
W1W2W3
W4
W6
W5
E1E2
E3
E4
N
Background noise
• Measure existing levels of noise prior to the wind farm development
• Determine statistical variation.
Background Noise
0
10
20
30
80 90 100 110 120 130 140 150 160 170 180
Sound Pressure Level (dB re 1 uPa)
Fre
qu
en
cy d
istr
ibu
tio
n (
%) 10 m
5 m
Overall Sound Pressure LevelNorth Hoyle
Background Noise
0
20
40
60
80
100
120
140
160
180
200
1 10 100 1000 10000 100000 1000000
Frequency (Hz)
Sp
ec
tral
lev
el (d
B r
e.
1 u
Pa
2/H
z)
Mean and 95% confidence interval
Background noise
0
10
20
30
40
50
0 10 20 30 40 50 60 70 80 90
dBht (species)
Fre
qu
en
cy
dis
trib
uti
on
(%
)
Salmon
Dab
Bottlenose Dolphin
Harbour Seal
Harbour Porpoise
Cod
Species perceived sound level (dBht)
Background NoiseSummary
• Shallow coastal waters are a noisy environment when compared with deep waters.
• Greatest variation caused by shipping movements (< 1 kHz).
Piling Noise
• Short duration impulse noise.
• Pile strike every 1 to 3 seconds for up to 6 hours.
• Piling operation takes many months
Underwater piling noiseHammering of a 4.3 m diameter pile,
measured at a range of 3.9 km.
Piling Noise Peak Sound Levels, 4.3 m diameter pile.
150
170
190
210
230
250
270
1 10 100 1000 10000 100000Range (m)
Pk
-pk
SP
L (
dB
re
. 1
uP
a) All transects
SL=260.31 dB re 1 uPa
TL=22 log R
Piling NoiseSpectral content at 1300 and 6000 m
0
20
40
60
80
100
120
140
160
180
200
1 10 100 1000 10000 100000 1000000
Frequency (Hz)
Sp
ec
tra
l le
ve
l (d
B r
e. 1
uP
a2/H
z)
1300 m
6000 m
Piling NoiseSpecies perceived sound level (dBht)
4.3 m diameter pile
40
60
80
100
120
140
160
180
200
1 10 100 1000 10000 100000
Range (m)
dB
ht(
Sp
ec
ies
)
Cod
Dab
Salmon
Bottlenose dolphin
Harbour porpoise
Harbour seal
90 dBht level
Further evidence
• Piling: World‟s largest offshore wind farm
was build on Horns Reef in the Danish North Sea in 2002; observations from ship surveys showed a significant change in behaviour of harbour porpoise on days with pile driving at distances up to 15 km from the wind farm
(Tougaard, J, Carstensen,J, Skov,H, Teilmann,J, and Henriksen, O D (2003). Effects from
pile driving operations on harbour porpoises at Horns Reef offshore windfarm, monitored
by T-PODs and behavioural observations. Report by National Environmental Reseach
Institute, Frederiksborgvej 399, DK-4000 Roskilde,Denmark)
Piling NoiseSummary
• Impact piling generates extremely high underwater sound levels, and should be regarded as capable of causing significant environmental effect.
• Development of mitigation measures ?
Operational Noise
• Subsea noise measurement from operational wind farm.
• Broadband noise for many years.
Operational noiseNorth Hoyle
0
20
40
60
80
100
120
140
160
1 10 100 1000 10000 100000 1000000
Frequency (Hz)
Pre
ss
ure
Sp
ec
tra
l D
en
sit
y
(d
B r
e.
1 u
Pa
2 /
Hz)
3 m range
10 m range
70 m range
100 m range
Background
Sea Sate Zero
Operational Noise
0
20
40
60
80
100
120
140
160
180
200
1 10 100 1000 10000 100000 1000000
Frequency (Hz)
Sp
ec
tral
lev
el (d
B r
e.
1 u
Pa
2/H
z)
Mean and 95% confidence interval
Operational NoiseSpecies Perceived Sound Levels
North Hoyle
0
10
20
30
40
50
0 10 20 30 40 50 60 70 80 90
dBht Species
Fre
qu
en
cy d
istr
ibu
tio
n %
Cod
Dab
Herring
Salmon
Bottlenose Dolphin
Harbour Porpoise
Harbour Seal
Conclusions(so far …)
• Shallow coastal waters are a noisy environment.
• Construction noise and particularly piling has the potential for significant environmental effect.
• Operational wind farm noise is marginally above shallow water noise and is therefore unlikely to adversely effect marine species.
Programme
• Blyth – Operational noise.
• North Hoyle – Background, construction noise.
• Scroby Sands – Background and construction noise.
Report: JR Nedwell, J Langworthy and D Howell. Assessment of sub-sea noise acoustic noise and vibration from offshore wind turbines and its impact on marine wildlife;
Initial measurements of underwater noise during construction of offshore windfarms and comparison with background noise. 544R0423, May 2003.
Programme
• North Hoyle – Operational noise.
• Scroby Sands – Operational noise.
• 1 x Construction noise.
• 2 x Operational noise.
Update on underwater noise and offshore wind farms.
Steve Parvin and Dr Jeremy NedwellSubacoustech Ltd
www.subacoustech.com