Featured Research

from universities, journals, and other organizations

Falling Snow Can Create A Noisy Nuisance ... Underwater

March 6, 2000
Johns Hopkins University
Snowflakes falling gently onto the water; nothing could be more quiet and peaceful... for humans. But new research shows these falling flakes can create an enormous racket to the ears of marine animals and sensitive sonar.

Tiny white snowflakes floating gently onto the glistening surface of a body of water.

For humans, it's hard to imagine a more quiet and peaceful scene. But to water animals with a keener sense of hearing, these falling flakes can create an enormous racket just below the surface, new research indicates. Noisy snowflakes can also pose problems for electronic "ears" by blurring sensitive sonar readings.

A team of researchers from four universities, including Johns Hopkins, produced these findings about snowflake sounds by analyzing recordings made underwater during winter storms. The researchers attributed the sub-surface noise to some unlikely culprits: oscillating bubbles, too small and short-lived to be seen by the naked eye. Their report was published in a recent issue of the Journal of the Acoustical Society of America.

The researchers concluded that as a snowflake falls onto a body of water, it deposits a tiny amount of air just beneath the surface. Before the bubble reaches the surface and pops, it sends out a piercing sound. "If you submerge a pocket of air trapped in a snowflake, that pocket of air cannot just sit there," explained Andrea Prosperetti, the Charles A. Miller Jr. Distinguished Professor of Mechanical Engineering at Johns Hopkins and a co-author of the article. "The bubble has to adjust its volume, and it will do so by oscillating. And when it oscillates, it emits noise."

This screeching sound, ranging from 50 to 200 kilohertz, is too high-pitched to be heard by human ears, which generally pick up nothing higher than 20 kilohertz. But the snowflake noise could be quite annoying to porpoises and other aquatic animals that can detect the higher frequencies, said Lawrence A. Crum, chair of the Acoustics and Electromagnetics Department at the University of Washington's Applied Physics Laboratory in Seattle. Falling snow can add 30 decibels to underwater noise levels, Crum said.

Crum, the lead author of the study, launched the research project several years ago when he and a colleague used sensitive hydrophones underwater microphones to capture the sound of snowflakes falling on a motel swimming pool in Roanoke, Va. When the recordings were analyzed, the acoustical "fingerprints" of the snowflake sounds were identical to those of bubbles.

Prosperetti, an internationally respected expert in bubble physics, was asked to join in the research because, with the same group, he had earlier conducted studies of underwater noise generated by raindrops. He developed a theoretical foundation to explain how tiny bubbles produced by falling snow could generate the type of sounds recorded by Crum and his colleagues. To do so, Prosperetti had to brush up on his snowflake science.

"Snow is incredibly complex," Prosperetti said. "The shape and size of a snowflake depends very critically upon the temperatures to which it has been exposed not just the temperature on the surface of the Earth but also in the cloud where it formed. We know that snowflakes are made of many ice crystals arranged together in such a way as to leave a lot of space for air because the density of a snowflake is about one-tenth the density of water. That means nine-tenths of the volume of a snowflake is air. When a snowflake strikes the water, it melts, and the air inside is freed up as a bubble. When that bubble oscillates, it makes noise."

Beyond its impact on water animals, this snowflake noise can create electronic "clutter" for people who use sonar devices to track migrating fish or to distinguish between natural and man- made underwater sounds. The new research could help engineers develop equipment that can filter out sounds made by snow falling on water.

The other co-authors of the journal article on snowflake noise were Hugh C. Pumphrey of the Department of Meteorology at the University of Edinburgh in Scotland and Ronald A. Roy of the Department of Aerospace and Mechanical Engineering at Boston University. The research was funded in part by the Office of Naval Research.

Story Source:

The above story is based on materials provided by Johns Hopkins University. Note: Materials may be edited for content and length.

Cite This Page:

Johns Hopkins University. "Falling Snow Can Create A Noisy Nuisance ... Underwater." ScienceDaily. ScienceDaily, 6 March 2000. <www.sciencedaily.com/releases/2000/03/000305122454.htm>.
Johns Hopkins University. (2000, March 6). Falling Snow Can Create A Noisy Nuisance ... Underwater. ScienceDaily. Retrieved August 22, 2014 from www.sciencedaily.com/releases/2000/03/000305122454.htm
Johns Hopkins University. "Falling Snow Can Create A Noisy Nuisance ... Underwater." ScienceDaily. www.sciencedaily.com/releases/2000/03/000305122454.htm (accessed August 22, 2014).

Share This

More Matter & Energy News

Friday, August 22, 2014

Featured Research

from universities, journals, and other organizations

Featured Videos

from AP, Reuters, AFP, and other news services

Is It a Plane? No, It's a Hoverbike

Is It a Plane? No, It's a Hoverbike

Reuters - Business Video Online (Aug. 22, 2014) UK-based Malloy Aeronautics is preparing to test a manned quadcopter capable of out-manouvering a helicopter and presenting a new paradigm for aerial vehicles. A 1/3-sized scale model is already gaining popularity with drone enthusiasts around the world, with the full-sized manned model expected to take flight in the near future. Matthew Stock reports. Video provided by Reuters
Powered by NewsLook.com
Coal Gas Boom in China Holds Climate Risks

Coal Gas Boom in China Holds Climate Risks

AP (Aug. 22, 2014) China's energy revolution could do more harm than good for the environment, despite the country's commitment to reducing pollution and curbing its carbon emissions. (Aug. 22) Video provided by AP
Powered by NewsLook.com
Former TSA X-Ray Scanners Easily Tricked To Miss Weapons

Former TSA X-Ray Scanners Easily Tricked To Miss Weapons

Newsy (Aug. 21, 2014) Researchers found the scanners could be duped simply by placing a weapon off to the side of the body or encasing it under a plastic shield. Video provided by Newsy
Powered by NewsLook.com
Flower Power! Dandelions Make Car Tires?

Flower Power! Dandelions Make Car Tires?

Reuters - Business Video Online (Aug. 20, 2014) Forget rolling on rubber, could car drivers soon be traveling on tires made from dandelions? Teams of scientists are racing to breed a type of the yellow flower whose taproot has a milky fluid with tire-grade rubber particles in it. As Joanna Partridge reports, global tire makers are investing millions in research into a new tire source. Video provided by Reuters
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.


Breaking News:
from the past week

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News


Free Subscriptions

Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile

Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?

Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins