Whales hear us more than we realize

whales-hear-us-more-than-we-realize

Killer whales and other marine mammals likely hear sonar signals more than we've known. That's because commercially available sonar systems, which are designed to create signals beyond the range of hearing of such animals, also emit signals known to be within their hearing range, scientists have discovered.

The sound is likely very soft and audible only when the animals are within a few hundred meters of the source, say the authors of a new study. The signals would not cause any actual tissue damage, but it's possible that they affect the behavior of some marine mammals, which rely heavily on sound to communicate, navigate, and find food.

The findings come from a team of researchers at the Department of Energy's Pacific Northwest National Laboratory, working together with marine mammal expert Brandon Southall of Southall Environmental Associates. The findings were published April 15 in the journal PLOS ONE.

A team led by Zhiqun (Daniel) Deng, a chief scientist at PNNL, evaluated the signals from three commercially available sonar systems designed to transmit signals at 200 kilohertz. The impact of such systems on marine mammals is not typically analyzed because signals at 200 kilohertz can't be heard by the animals.

The team found that while most of the energy is transmitted near the intended frequency of 200 kilohertz, some of the sound leaks out to lower frequencies within the hearing range of killer whales and other animals such as harbor porpoises, dolphins and beluga whales. The three systems studied produced signals as low as 90, 105 and 130 kilohertz.

At the levels measured, the sounds would be quieter than many other sounds in the ocean, including the sounds the animals themselves make, and they wouldn't be heard at all by the animals beyond a few hundred meters.

"These signals are quiet, but they are audible to the animals, and they would be relatively novel since marine mammals don't encounter many sounds in this range," said Southall, who is the former director of the Ocean Acoustics Program of the National Oceanic and Atmospheric Administration.

"These sounds have the potential to affect animal behavior, even though the main frequency is above what they primarily hear. It may be that environmental assessments should include the effects of these systems. This may not be a major issue, but it deserves further exploration," added Southall.

The new findings have their roots in a project to track marine mammals in Puget Sound, which was part of a broader effort to provide information on the environmental impact of a planned tidal energy project there near Seattle. Researchers had planned to use sonar to help locate killer whales, but some marine mammal experts had observed that the animals might actually be hearing the sonar. Those observations led to the study, which was funded by the Department of Energy's Office of Energy Efficiency and Renewable Energy.

How do the sonar signals actually sound to marine mammals like killer whales? Since high-frequency sonar pings several times per second, it's possible that it sounds like one continuous, high-pitched hum or ping.

"If you think of a keyboard on a piano, the ships would be hitting the low notes quite hard, the middle keys would be most of the sounds of the animals themselves, and the sonar systems we studied would be relatively quieter sounds in the top few octaves on the right of the keyboard," said Southall.

The authors of the paper did not directly study the hearing capability of whales and other marine mammals. Instead, the study focused on the sounds produced by sonar systems, discovering that commercial sonar systems are emitting signals within the animals' known hearing range. Deng and colleagues are currently considering ways to limit signal leakage to reduce the amount of sound from high-frequency sonar systems that would be audible to marine mammals.

Source: DOE/Pacific Northwest National Laboratory 

Reference:

Z. Daniel Deng, Brandon L. Southall, Thomas J. Carlson, Jinshan Xu, Jayson J. Martinez, Mark A. Weiland, and John M. Ingraham, 200 kHz commercial sonar systems generate lower frequency side lobes audible to some marine mammals, PLOS ONE, April 2014, http://dx.plos.org/10.1371/journal.pone.0095315.

Featured image: Sperm whale off the coast of southern California. Image credit: Photo taken under NMFS permit #14534; Author: A. Friedlaender

If you value what we do here, create your ad-free account and support our journalism.

Share:

Producing content you read on this website takes a lot of time, effort, and hard work. If you value what we do here, select the level of your support and register your account.

Your support makes this project fully self-sustainable and keeps us independent and focused on the content we love to create and share.

All our supporters can browse the website without ads, allowing much faster speeds and a clean interface. Your comments will be instantly approved and you’ll have a direct line of communication with us from within your account dashboard. You can suggest new features and apps and you’ll be able to use them before they go live.

You can choose the level of your support.

Stay kind, vigilant and ready!

$5 /month

  • Ad-free account
  • Instant comments
  • Direct communication
  • New features and apps suggestions
  • Early access to new apps and features

$50 /year

$10 /month

  • Ad-free account
  • Instant comments
  • Direct communication
  • New features and apps suggestions
  • Early access to new apps and features

$100 /year

$25 /month

  • Ad-free account
  • Instant comments
  • Direct communication
  • New features and apps suggestions
  • Early access to new apps and features

$200 /year

You can also support us by sending us a one-off payment using PayPal:

One Comment

  1. Sacred Sonic Geometry, music is in everything, every object emits a certain tone. A mathematical universal language tho separately invent means the same thing through-out Antiquity with no barriers, oceans or cultural beliefs to divide them from their true meaning. The sounds and symbols of ancient antiquity could in fact unlock the mysteries of our universe. Resonating sound waves can travel through anything. An invisible energy force that was created at the beginning of time. The secrets of CERN the atomic energy Collider that can split the atoms in order to discovered the creation of the God Atom discovered in reality sound waves of energy. These sound waves once created will last forever, creating a life of their own, traveling through both space and time for an eternity,… Perhaps one day we will be able to capture and listen to ancient sound waves enabling man to travel back in time in the same way or manner we can see our past in the universe through super powerful telescopes pointing into deep space. The language of whales is a very complex multidimensional set of sound waves that are millions of years old and are the loudest octaves created by a living organism in nature. Today we are destroying these magnificent creatures and with their destruction we will be unable to discover and unlock the secrets of our universe, losing our ability to travel back in time or our ability to see clearly into our future. Thomas DeSoto

Leave a reply