Follow this link to skip to the main content
Discovery of Sound in the Sea
search
Jump to Topic:
Facts and Myths

The topic of underwater sound is complex and requires a foundation in multiple sciences to fully comprehend. It becomes even more complicated when animals are exposed to anthropogenic sounds in the marine environment. Scientists are just beginning to explore the questions that need to be answered. The scientific process is at work, and it will take time to get these answers, but we are making progress with new discoveries occurring all the time.

This quiz focuses on the science of underwater sound - what is known and what is not known. Your challenge is to determine whether each statement listed below is a fact (something that has been verified to be accurate through the scientific process) or a myth (something that is believed to be false). Once you decide, click on the gold "Answer" box and you will get the accurate response along with links back to places in the DOSITS website where you can get more information on the topic.

Good luck!

1.
The greatest uncertainty in understanding the effects of underwater sound on marine animals is knowing how sound propagates.
This is a MYTH
Determining whether a sound will affect a marine animal requires knowing both how the sound will spread or propagate and how well the animal can hear the sound. The greater uncertainty is in the animal data. Scientists know a great deal about the physics of sound in water and much less about how or what marine animals hear.

Read more on these DOSITS pages:
How do you determine if a sound affects a marine animal?
Sound Movement

2.
Sound rapidly gets weaker as it moves away from a source.
FACT
If we think about sound as a rock thrown into a pond and look at the pond from the side, you will notice that the wave gets smaller as it moves away from the place where the rock fell (the source of the waves). The wave gets smaller because it spreads out and because some of the sound energy is absorbed by seawater.

Read more on these DOSITS pages:
Why does sound get weaker as it travels?
Cylindrical vs. Spherical Spreading (Advanced Topic)

3.
Sounds from World War II are still circling the globe, trapped in the sound channel.
Myth
The sound (SOFAR) channel was discovered in World War II. Sounds travel further in the SOFAR Channel than in other parts of the ocean, but all sounds in water scatter and vanish, just as in air.

Read more on these DOSITS pages:
The SOFAR Channel
History of the SOFAR Channel

4.
Background sounds heard by porpoises are dominated by human noise.
MYTH
Porpoises and other odontocetes (toothed whales) hear best at high frequencies (60-120 kHz and 20-50 kHz, respectively), whereas background or ambient noise is primarily due to humans (noise generated by distant shipping) in the frequency range of 20-500 Hz.

Read more on these DOSITS pages:
What are common underwater sounds?
What sounds can animals hear?

5.
Background sounds heard by the large whales are dominated by human noise.
FACT
The large whales include all species of baleen whales, such as blue, fin, and humpback whales. There are no direct measurements of the hearing abilities of baleen whales. Anatomical evidence and vocalizations suggest that they are adapted to hear best at low frequencies (20 Hz to 2 kHz). Background or ambient noise is primarily due to humans (noise generated by distant shipping) in the frequency range of 20-500 Hz, which overlaps the frequency range at which the large whales are believed to hear best.

Read more on these DOSITS pages:
What are common underwater sounds?
What sounds can animals hear?

6.
Scientists understand how important the effects of anthropogenic sounds are on marine animals.
MYTH
Researchers suggest that increased background noise and specific sound sources might impact marine animals in several ways. However, much more research is needed to understand the potential impacts. It is also not clear how important these impacts are to the well being of the animals and their populations.

Certain sounds might:

  • cause marine animals to change their behavior
  • prevent marine animals from hearing important sounds (masking)
  • cause hearing loss (temporary or permanent) or tissue damage in marine animals.

Read more on these DOSITS pages:
What are the effects of anthropogenic sound on marine animals?

7.
Most marine mammal strandings are due to underwater sound.
MYTH
Observations as far back as Ancient Greece show that marine mammals have been stranding for millennia. There are many potential causes of strandings, including disease, ship strike, pollution exposure, etc. One controversial and unresolved issue is how the use of military sonar relates to strandings, particularly strandings of some species of beaked whales. In several cases worldwide, there is sufficient information about military sonar operations, the times and locations of the strandings to connect the strandings with sonar use. In the last fifty years, in all possible sonar related events, fewer than 50 animals are known to have stranded. In comparison, about 1,000 cetaceans and 2,500 pinnipeds strand annually in the U.S. alone.

Read more on these DOSITS pages:
What are the effects of anthropogenic sound on marine animals? - Strandings

8.
Marine mammals must be able to hear a sound in order for it to affect their behavior.
FACT
Hearing is the universal alerting sense in all vertebrates. Sound is so important because animals are able to hear events all around them, no matter where their attention is focused. Many species of blind amphibians, reptiles, fishes and mammals are known, but no naturally profoundly deaf vertebrate species have been discovered. Although hearing is important to all animals, the special qualities of the undersea world emphasize the use of sound.

Read more on these DOSITS pages:
How do you determine if a sound affects a marine animal?

9.
Marine mammals use sound to communicate, navigate, and locate prey.
FACT
Marine animals use sound in the sea to accomplish many tasks. Since light travels relatively short distances in the ocean, sound is often used by animals for such basic activities as finding food or a mate, navigating, and communicating.

Read more on these DOSITS pages:
Why is sound important to marine animals?

10.
Like marine animals, people use sound underwater to accomplish many of the tasks for which we use light in air.
FACT

People use sound in the sea for activities such as research, exploration, navigation, fishing, and communication.

Read more on these DOSITS pages:
People and Sound
How do people and animals use sound in the sea?

11.
Decibel levels in air are the same as decibel levels in water.
MYTH
The decibel is a relative unit of measure, not an absolute one. Confusion arises because relative intensities in water are referenced to 1 microPascal (µPa) whereas sound waves in air are referenced to 20 microPascals (µPa). The intensity of a sound wave depends not only on the pressure of the wave, but also on the density and sound speed of the medium through which the sound is traveling. Therefore, relative sound intensities given in dB in water are not the same as relative sound intensities given in dB in air

Read more on these DOSITS pages:
How does sound in air differ from sound in water?
Introduction to Decibels (Advanced Topic)
What units are used to measure sound?

12.
Sound travels faster in water than in air.
FACT
Sound moves about 1500 meters per second in seawater. That's approximately 15 football fields end-to-end in one second. Sound moves much more slowly in air, at about 340 meters per second, only 3 football fields a second.

Read more on these DOSITS pages:
How fast does sound travel?

13.
The impact of sound on marine life is magnified because sound travels faster through water than it does through air.
MYTH
Sound is energy that travels through a medium, such as air or water. It has a different speed in each medium based on the characteristics of the medium. Sound does travel faster in water than in air. Sound travels approximately 1500 meters per second in seawater, but only approximately 340 meters per second in air. However, the speed at which sound travels is not directly related to its impact. Impact is related to energy received for a given sound and whether the animal can hear the sound. The sound intensity received by the animal, the frequencies the sound contains, and the sensitivity of the species in the area are all important for understanding if a sound may impact an animal.

Read more on these DOSITS page:
What is sound?
How fast does sound travel?
How do you determine if a sound affects a marine animal?

14.
Sound can be used to measure ocean temperature, currents and waves.
FACT
People routinely use sound in the sea for many applications. Because sound travels or propagates differently with different temperatures, currents, and waves, the precise measurements of sound propagation can be used to collect information about the ocean's characteristics.

Read more on these DOSITS pages:
How is sound used to research ocean physics?

15.
Fish species produce many sounds, including grunts, croaks, clicks, and snaps.
FACT
Fishes produce a variety of sounds using different mechanisms and for different reasons. The three main ways fishes produce sounds are by striking or rubbing together skeletal components, using sonic muscles that are located on or near their swim bladder, and by quickly changing speed and direction while swimming. The majority of sounds produced by fishes are low frequency, typically less than 1000 Hz.

Read more on these DOSITS pages:
How do fish produce sounds?
Audio Gallery: Fishes

16.
Stranding events involving multiple beaked whales have coincided closely in time and space with military activities using sonar.
FACT
Investigating the cause of a stranding is very difficult, because scientists must try to reconstruct what happened after the event, have little or no history on the individual animals, and, as a result, can generally draw firm conclusions in only about half of all strandings. However, in four well-documented cases, there is sufficient information about the sonar operations, the times and locations of the strandings, and the injuries to the animals to associate the strandings with sonar use. These events occurred in Greece (1996), the Bahamas (2000), Madeira (2000), and the Canary Islands (2002).

Read more on these DOSITS pages:
What are the effects of anthropogenic sound on marine animals? - Strandings

17.
Anthropogenic sound is the leading cause of marine mammal deaths.
MYTH
Marine mammals face threats from many different human activities, including fishing, habitat destruction, ship strikes, whaling, and sound production. Of these threats, fisheries bycatch kills the most marine mammals. Globally, it is estimated that more than 650,000 marine mammals are killed annually by being accidentally caught in fishing nets (Read et al., 2006)

Read more on these DOSITS pages:
What are the potential effects of anthropogenic sound on marine animals?

18.
In almost all cases, hearing loss due to noise does not occur if the frequency of the sound to which the animal is exposed is outside the range that the animal can hear.
FACT
Hearing loss from sound exposure depends mostly on the sensitivity of the animal to a sound and the interaction of three characteristics of the sound: the frequency of the sound, the intensity of the sound, and the duration or how long the animal is exposed to that sound. Hearing loss does not usually occur if the frequency of the sound to which the animal is exposed is outside the range that the animal can hear. However, one other factor, the rise time of the sound, or how long it takes the sound to reach its highest intensity level, is also important. Very sharp rise times, which can occur with very intense impulse noises, can compound an injury and, in some extreme cases, can impact ears even though the peak frequency of the sound is not in the normal hearing range of the animal.

Read more on these DOSITS pages:
How do you determine if a sound affects a marine animal?
What are the effects of underwater sound on marine mammals?

19.
The only way to reduce the potential effects of anthropogenic sound on marine life is to eliminate the sound source.
MYTH
A variety of approaches have been used to reduce the potential effects of anthropogenic sound, although the extent to which these measures are effective has not been determined:

  • Avoiding marine mammal habitats.
  • Detecting animals and modifying the sound-producing activities.
  • Modifying the sound source.
  • Ramping-up the sound signal intensity.
  • Sound screening.

Read more on these DOSITS pages:
How can we moderate or eliminate the effects of human activities?

20.
There is scientific uncertainty about how underwater sound may be affecting marine life.
FACT
Researchers suggest that increased background noise and specific sound sources might impact marine animals in several ways. The effects vary depending upon the intensity and frequency of the sound, and other variables. It is also not clear how important these impacts are to the well being of the animals and their populations.

Read more on these DOSITS pages:
What are the effects of anthropogenic sound on marine animals?
Scientific Uncertainty
Scientific Method

21.
Low-frequency sound levels in the ocean have increased since the introduction of steam-powered shipping.
FACT
In the frequency range of 20-500 Hz, ambient noise is primarily due to noise generated by distant shipping. Noise generated by shipping has increased as the number of ships on the high seas has increased.

Read more on these DOSITS pages:
How does shipping affect ocean sound levels
What are common underwater sounds?

22.
Science strives to be objective. Feelings and religious or political views should not influence research or conclusions.
Fact
Scientific investigations are based on observations, measurements, and reproducible experimentation. Science is a process for asking questions about the natural world and testing the answers. Personal feelings and religious or political views should not be incorporated into the development of hypotheses, theories, or conclusions.

Read more on these DOSITS pages:
Scientific Method
Scientific Uncertainty

23.
One way to arrive at "scientific truth" is to conduct an opinion poll of scientists.
MYTH
The Scientific Method is an orderly process for asking questions about the natural world and testing the answers. Hypotheses that have been consistently validated through observations or experimentation can eventually be advanced to the status of theory. A theory is a thoroughly substantiated explanation of some aspect of the observable world. Theories come as close to objective truth as possible.

Read more on these DOSITS pages:
Scientific Method
Scientific Uncertainty