BOAT ENGINES AFFECT WILDLIFE, AND MAJOR
IMPROVEMENTS ARE 
POSSIBLE
PROPELLER GUARDS keep people and animals in the water from being gashed by propellers. While propeller guards have trade-offs, and boats can still hit cetaceans, propeller guards are a safety item which can help performance: "concentric ring vanes (looks like a bullseye target from the rear)... are said to improve handling at slower speeds, increase thrust, and slightly increase top speeds in some situations."
propellersafety.com/propeller-guard-design-trade-offs
Many articles about propeller guards are at propellersafety.com/
Simple guards are widely sold for $100 to $500.
US Coast Guard proposals on propeller guards are reviewed at:
propellersafety.com/proposed-propeller-guard-regulations/
Jet boats use a water pump in the hull, with no propeller below water, reducing dangers of cutting large animals, and reducing noise underwater. Dangers remain for animals smaller than the water intake; they can be sucked through the pump.
ENGINE NOISE varies, based on engine size, propeller design, gears, whether exhaust (and noise) are discharged in air or, more often, underwater.
Basics https://wildwhales.org/?s=noise
- Underwater sound intensity is compared to a change in sound pressure of 1 micro Pascal (1 µPa) at a distance of 1 meter from the source.
In air, a higher standard reference
sound pressure of 20 micro Pascals is used. - The result is that any specific sound energy is reported with a number 26 dB higher underwater than the number which would be reported in air.
- "Propeller noise from a fast power boat with a 160 dB source level will be heard as a 135 dB noise at a distance of about 20 metres from the boat, but will still be at ~70 dB 14 km from the boat – enough to mask other whales calls and interfere with the ability of whales to locate prey. If multiple vessels are present their noise will add to a louder noise, although this addition is complex: two vessels producing 140 dB sounds side by side will appear to produce 146 dB noise together."
Aquo.eu has broad research on underwater noise.
The European Union has a Technical Group on reducing ocean noise
Ireland
has a detailed survey of noise sources in the
Atlantic west of Ireland 2015-2016. Passing ships were recognizable (p.62) on
underwater hydrophones for 3-4 hours, at 108-112 dB re 1μPa. Three seismic
vessels were present during monitoring, up to 150 km away, with sounds up to
145 dB re 1μPa2.s (SEL).
Whales:
- Nearly 3.8 million detections of echolocation clicks
and 375,000 tonal whistles were collected during 1,657 days of static
acoustic monitoring (p.65) Each species
is reported by month and location.
- Five species of baleen whales were identified: blue,
fin, sei, humpback and minke whales.
- Twenty species of cetacean overall were recorded, analysed and mapped with almost 2,200 sighting records
over the two-year field study.
- Cumulative abundance of 380 Sperm whales was found
using acoustic detection and tracking methods.
- Species such as the Beluga/White whale were found - a
mainly Arctic species
- Minke whales were the most frequently observed and
abundant baleen whale species, numbering approximately 12,000 in summer
and 5,000 in winter and there were significant sightings of Minke whale
calves
- Fin whales occurred in Irish waters both in summer
and winter, the analysis showing the continental slope and nearby deep
waters to be an important area for this species, possibly for feeding
and/or migration.
- Many sound recordings were made of rarely-seen beaked
whales, which are deep-diving offshore species poorly known to science.
- At least three species of beaked whales were recorded
during the ObSERVE surveys, primarily in deep
oceanic waters along the continental margin, the Porcupine and eastern Rockall Basins. The records collected during the
aerial project were sufficient to provide the first estimates recorded for
this study area of 2,500 individuals in summer and 4,000 in winter.
- Endangered Blue whales could be detected underwater
up to 115-200km away and strong seasonal patterns in their sounds were
noted and described.
Dolphins:
- Considerable variation was found in the distribution,
abundance and movements of dolphin species
- Bottlenose dolphins were much more abundant during
the winter than the summer, with densities in the second winter (2016-17)
being among the highest ever recorded.
Ireland at the same time did aerial and bird surveys.
Vancouver’s Port has
- discounts on harbor fees to quiet ships, based on "three quiet-vessel ship classifications and three propeller technologies shown to reduce underwater noise."
- Hemmera's study reviews how well many approaches reduce noise, such as propeller design, cleaning, and vibration isolation. portvancouver.com/wp-content/uploads/2017/01/Vessel-Quieting.pdf
- portvancouver.com/wp-content/uploads/2016/04/ECHO-Program-Underwater-Noise-Infographic-April-2016.pdf
- portvancouver.com/wp-content/uploads/2015/03/2008-10-23 Presentation to DCLC on the Marine Mammal Monitoring program by Jacques Whitford.pdf
Specific Boat Engines' Sound, Measured
Underwater
A Finnish study (Seppänen and Nieminen 2004) compared noise from several boats underwater in a lake in Finland, in the summer of 2002. geophysica.fi/pdf/geophysica_2004_40_1-2_023_seppanen.pdf
A 100 HP outboard motor with exhaust underwater was louder underwater than a larger boat with diesel inboard engines.
The diesel boats did not put exhaust below water.
Jet boats use a water pump in the hull, with no propeller below water, and had less noise underwater than other boats tested.
|
Vessels on Lake |
Sound Pressure Level in
Decibels, Relative to 1 Micro-Pascal of Pressure,
at 50-100 meters |
|
Outboard Yamaha 100 HP, 4-Stroke |
140 |
|
Slow Steel Boat, Diesel |
133 |
|
Outboard Yamaha 15 HP |
129 |
|
Outboard Johnson 55 HP |
128 |
|
Outboard Johnson 20 HP |
125 |
|
Fast Jetboat, Diesel |
125 |
geophysica.fi/pdf/geophysica_2004_40_1-2_023_seppanen.pdf
Specific Boat Engines' Sound, Measured in
Air
Boating, a powerboat magazine, measured noise of a Canadian electric boat engine in 2012 in air, in a prototype boat, boatingmag.com/boats/electric-motor-boats
Ski Nautique boat with LTS Marine engine, 206-hp maximum power, 79dB-A on the boat, or silent at idle
"Typically, our idle speed test numbers fall in the 60s [dBA, on non-electric boats], the same level as a casual conversation. As the boat climbs on plane, the engine noise revs up into the 70s. Then it climbs into the 80s at cruising speeds and into the 90s as it nears wide-open throttle; some noisy boats hit the 100s."
A consultant for an oyster company measured boat noises in air, in 2011, in California (p.36).
nps.gov/pore/learn/management/upload/planning_dboc_sup_background_environ_comments_111209.pdf (p.36 of pdf file)
Oyster skiff Powered by 20 HP, 4-Cycle Engine at 50 feet: 62 dBA Lmax, 58 dBA Leq
Oyster Skiff Powered by 40 HP, 4-Cycle Engine at 50 feet: 63 dBA Lmax, 60 dBA Leq
National Park Service overview
A widely-quoted 1995 study submitted to the New Jersey state police by the testing company Noise Unlimited, compared noise in air from several boats, apparently in 1995.
oysterzone.files.wordpress.com/2012/03/noise-unlimited-1995.pdf
The Personal Watercraft Industry Association says personal watercraft became 70% quieter after 1998, and presumably some other engines are also quieter.
|
Type of Boat |
dBA at 50 feet |
|
Classic Inboard - 1930 Wooden ChrisCraft, Inboard Motor, Exhaust Outlet Above the Water Line |
72 |
|
Single Outboard Engine - Police Patrol Boat with single 175 hp Johnson Outboard Motor |
81 |
|
Twin Outboard Engine Police Patrol Boat with two 155 hp Evinrude Outboard Motors |
82 |
|
Personal Watercraft No. 1 - Kawasaki JetSki 750 cubic centimeter engine |
81 |
|
Personal Watercraft No. 2 - Kawasaki 900 cubic centimeter 3 cylinder 100 hp, High Performance Model |
76 |
|
Inboard/Outboard with Exhaust Below Water Line - 350 cubic inch (ci) Chevrolet Engine with Outboard Drive |
85 |
|
Inboard/Outboard with Exhaust Above Water Line - Wellcraft Nova 352 ci Engine with Outboard Drive |
90 |
|
Racing Boat No. 1 - Runabout, 283 ci Chevrolet Engine Exhaust Below Water Line |
105 at 77 mph |
|
Racing Boat No. 2 - Hydroplane, 305 ci Chevrolet Engine |
109 at 107 mph |
|
* A-Scale Sound level (dBA) measurements at a distance of 50 feet. A-Scale approximates the sensitivity of the human ear and is used to note the intensity or annoyance level of sounds. Data from NUI Report No. 8077.1, New Jersey State Police-Marine Division. Nov. 1, 1995. |
|
Overall Patterns of Noise
Boat speed is the strongest cause of noise, not boat size. Houghton et al. 2015 measured sound received by whales (with meters attached by suction cups), and characterized boats present (laser measurement). journals.plos.org/plosone/article?id=10.1371/journal.pone.0140119
baleinesendirect.org/en/boat-speed-noise-responsible-for-disturbance-of-killer-whales/
Proposal for Quiet
Zones, where there are many marine mammals and few noises.
sciencedirect.com/science/article/pii/S0025326X1530028X
Maps on right show where quiet zones could be established
without much resistance, because there is not much noise there now. (Williams, Erbe, Ashe, Clark, 2015)
Reducing noise and whale fatalities in the St. Lawrence Estuary. Voluntary efforts by ships to avoid whale feeding areas and reduce speeds from 13 knots to 10 knots achieved a 36% or more reduction in the odds of whale deaths caused by ships, between 2013 and 2015. http://www.qc.dfo-mpo.gc.ca/infoceans/201410/article7-eng.html
Overall Effect of Boats in Orca Habitat.
US study (Veirs and Veirs 2007) measured sound in Orca habitat off Washington state from April 2004 to November 2005.
The quietest noise level (average for 30 minutes, 100-1,500 hz) was 95 dB, relative to 1 micro-pascal of pressure. They considered this "background" noise.
The loudest half hour averaged 130 dB. The difference of 35 dB means it was 56 times as loud.
"Large vessels like tankers, container carriers, ocean liners, fishing vessels, and tugs (hereafter "ships") pass in the shipping channels on the order of a kilometer from the hydrophones and create broad peaks in amplitude, typically lasting 15-60 minutes and having maximum amplitude ~20 dB above ambient" sound (10 times as loud as background, bold added).
"Each ship usually adds 20-25 dB [10-18 times as loud]...; some add nearly 30 dB [32 times] and a few add only 10 dB [3 times]"
"The relatively quiet periods between ships are usually less than 30 minutes, but sometimes last a few hours, particularly during the early morning hours."
"Small vessels like recreational power boats, whale watch boats, and sail boats under power (hereafter "boats") also add ~20 dB ... boats pass faster and closer to the hydrophones, typically creating a spike in amplitude that lasts a few minutes." (also 10 times as loud as background)
"boats usually add 15-20 dB. [6 to 10 times as loud as background]"
The graph of Sound Pressure Levels (SPL) shows that on summer days, noise is almost never under 110 dB [6 times background], and 60% of the time it is under 121 dB, so 40% of the summer days the sound is over 121 dB, 20 times background levels. In winter, 40% of the time sound is over 117 dB, 13 times background.
SPL
means "Sound Pressure Level" or Loudness
SPL means "Sound Pressure Level" or Loudness
Other Links on Noise
A US boat builders' group summarizes the history of US noise limits and proposals in air, without considering underwater life.
nmma.org/assets/cabinets/Cabinet520/Model_Noise_Act_History,_Status,_etc.doc
Erbe 2002 Noise levels of orca-watching boats.
https://aeinews.org/aeiarchive/docs/MMSwworca.pdf
1,000 narwhals died trapped under ice in 2008, because they did not leave their summer area before it froze over. Researchers believe the reason they did not leave was a seismic survey with air guns on their migration route. The seismic survey had "four arrays of up to 37 airguns with a combined maximum volume of 4200 inch3 and a pressure of 2000 psi."
YouTube.com/watch?v=bo_GZ3q_Ays
Scholarly articles on dolphins, whales and sounds