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More than 1.000 metres below the surface of the oceans. darkness dominates Marine creatures rely on sound for navigation, communication, and searching for food However, this way of life has come under threat from shipping, contributing to a rise in underwater volume of approximately 3.3 decibels(分贝)per decade. The trend shows little sign of levelling off.
With roughly 90% of trade relying on shipping, quieting the ocean through reductions in shipping itself is untenable . While efficiency improvements of shipping may cut noise, experts say more is needed. That is why technologies like modified propellers (螺旋浆) and noise-reducing materials are being developed to help humans and marine life coexist.
Much of the underwater noise a ship produces comes from its propeller. Spinning blades (浆叶) create low pressure, causing the water to boil and produce bubbles, a process known as cavitation(空化现象).When those bubbles collapse, a low-frequency noise is produced, disrupting the movements of marine lives.
One solution, being developed by researchers at the University of British Columbia, integrates flexible polymers(聚合物)into the metal propeller blades allowing their tips to bend and twist. This movement prevents bubbles from forming and thereby reduces the noise the blades produce. Based on simulations, the design could reduce cavitation noise by 20 decibels. Dr Jaiman says researchers intend to start testing a model next year.
Cavitation can also be reduced by increasing the number of bubbles, rather than reducing them. Researchers at MARIN, a Dutch research institute, have blown bubbles onto a propeller's blades, which can dampen the resulting noise. Model-scale tests of this system showed a 12-decibel decrease in low-frequency noise. But shipping noise does not come only from the propeller, with roughly 20% coming from engines and generators. To reduce this, MARIN researchers have experimented with a bubble screen generated from tubes positioned in belts around the outside of the ship These bubbles prevent noise from spreading.
1. Which best explains the underlined word “untenable” in paragraph 2?
A. Impractical.
B. Unavailable
C. Unstable.
D. Immeasurable.
2. What is the main source of underwater noise from ships?
A. The spinning blades.
B. The process of cavitation.
C. The engines and generators.
D. The bubbles generated by ships.
3. What solution is being developed at MARIN?
A.Boosting ship efficiency.
B. Creating flexible blade tips.
C. Generating more bubbles on blades.
D. Using quieter engines and generators.
4. What's the passage mainly about?
A. Strategies to prevent ships from making noise
B. Innovations to minimize underwater ship noise
C. Adapted propeller designs to restore undersea quiet.
D. Negative impacts of underwater noise on marine life
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