What is infrasound?
Infrasound is known as a low-frequency sound that is below the audible range of human hearing, typically below 10 Hz. Underwater speakers – also known as sound projectors – are devices used to transmit sound waves through water, often for communication or navigation purposes.
It’s worth noting that hearing sensation does not suddenly disappear at 16 Hz, commonly considered as 20 Hz. Instead, it persists down to very low frequencies of several hertz. As such, it is not possible to clearly define an inaudible infrasound range and an audible audio range as separate regions, unless we restrict the infrasound range to naturally occurring infrasound of very low frequencies.
Infrasound definition. A graphic definition
The graph on the right helps us to understand what infrasound is and its relationship to the hearing threshold.
The range of sound pressure level contours at 1000 Hz spans 100 dB, while at 16 Hz, the range is reduced to around 50 dB. However, you will notice that sound pressures are higher at low frequencies than at high frequencies.
The decrease in the range of sound pressure level contours at lower frequencies is due to the way that the human ear perceives sound. The human ear is less sensitive to low-frequency sounds, and so the perceived loudness of a sound does not increase as quickly as the sound pressure level increases. This means that at lower frequencies, a larger increase in sound pressure level is required to produce a noticeable increase in perceived loudness.
While sounds at very low frequencies may not be audible in the traditional sense, they can still have effects on the body and mind, such as causing vibrations that can be felt or producing sensations of pressure in the ears. To learn more about infrasound
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Examples of natural infrasound
Some natural phenomena produce infrasound, including avalanches, earthquakes, volcanic eruptions, ocean waves and waterfalls. Volcanoes, for example, produce atmospheric infrasound with frequencies ranging from ~ 0.01 to 20 Hz.
It has been identified that some terrestrial and aquatic animals can perceive infrasound by hearing it or detecting the movement of particles produced by the sound wave.
Natural sources of infrasound include:
- Earthquakes. Earthquakes generate low-frequency sound waves that travel long distances through the earth’s crust.
- Volcanic eruptions. Explosive volcanic eruptions can generate powerful infrasound waves.
- Thunderstorms. Lightning strikes during thunderstorms can produce low-frequency sound waves.
- Wind. Strong winds can generate infrasound waves, which can be heard as a low rumbling sound.
- Ocean waves. Large waves in the ocean can produce infrasound waves.
Human-generated (anthropogenic) sources of infrasound include:
- Ships can produce infrasound through various means, including the movement of their propellers and engines, as well as through sonar and acoustic communication systems. In some cases, the sound produced by ships can be intense enough to cause hearing damage or other physiological harm to marine animals that are exposed to it for prolonged periods of time. Efforts have been made to reduce the impact of ship-generated noise on marine life, such as through the development of quieter propellers and engines, and by implementing speed limits and other measures to reduce the intensity of sound produced by ships.
- Drilling and pile driving. To extract fossil fuels or installing monopiles for wind turbines.
- Underwater explosions: Explosions, such as those from underwater demolition or military activities, can produce powerful infrasound waves that travel long distances through the water.
- Seismic surveys: Seismic surveys are used to locate oil and gas reserves under the ocean floor. They involve the use of airguns, which produce high-intensity sound waves that penetrate the seafloor and bounce back to the surface, providing information about the geology of the area.
It’s worth noting that anthropogenic (human-generated) sound in the ocean, including infrasound, can have negative impacts on marine life, such as disrupting communication, causing stress, and even leading to hearing damage or death in some cases.
What Animals Can Hear Infrasound, and How Do They Use It?
Many underwater animals can hear infrasound. Here are some examples.
- Whales have specialized ear structures that allow them to detect infrasound for communication and echolocation.
- Dolphins have sensitive ears that can detect infrasound for communication and echolocation.
- Sharks: Some species of sharks can detect infrasound for hunting and navigation.
- Sea turtles have sensitive hearing and can detect infrasound for communication and navigation.
- Some species of rays can detect infrasound for communication and hunting.
- Squid: Squids produce infrasound for communication and hunting.
- Fish: Some species of fish generates infrasound for communication and navigation.
- Octopus: Octopuses produce infrasound for communication and territorial displays.
Several species of fish produce infrasound for communication and navigation. Here are some examples:
- Cod: Cod produce infrasound during mating and spawning.
- Haddock: Haddock produce infrasound during mating and spawning.
- Catfish: Catfish produce infrasound for communication and navigation.
- Goldfish: Goldfish produce infrasound for communication.
- Oyster toadfish: Oyster toadfish produce infrasound for communication and territorial displays.
- Croakers: Some species of croakers, including the Atlantic croaker, produce infrasound for communication and navigation.
- Salmon: Salmon produce infrasound for communication and navigation during spawning.
These fish produce infrasound by vibrating their swim bladder or other internal organs, which creates sound waves that can travel long distances underwater. This ability to produce and detect infrasound is crucial for their survival, allowing them to communicate, navigate, and locate prey or mates even in murky or dark environments.
Infrasound Underwater Speaker
Infrasound submarine speakers are specialized devices that can emit low-frequency sound waves. These devices can be used for a variety of purposes, such as underwater communications, imaging the seabed, acoustic sensing applications navigation, emulating anthropogenic and naturally occurring sounds and studying marine life.
Infrasound submarine speakers are a crucial component of underwater communication systems that operate in the infrasonic range. These speakers are specially designed to emit low-frequency sounds that can travel long distances through water, making them ideal for use in submarines, underwater research vessels, and oceanic monitoring systems.
Infrasound underwater projectors can also be used for scientific research, such as studying the behaviour of marine mammals. The use of infrasound in these applications can provide valuable insights into underwater environments that are difficult to study using other methods.
How do researchers use underwater infrasound speakers?
Underwater infrasound projectors are used in a variety of research applications, such as studying the behaviour of marine animals and exploring the geology and topography of the seafloor.
One common use of underwater infrasound projectors is to study the vocalizations and behaviour of marine mammals, such as whales, dolphins, and seals. These animals use low-frequency sounds to communicate over long distances and to navigate in the underwater environment. Researchers can use infrasound projectors to play back recorded sounds or to generate synthetic sounds to elicit specific responses from these animals. This can help them to better understand the vocalization patterns and behaviour of marine mammals and to assess the impacts of anthropogenic noise on these animals.
Underwater infrasound projectors can also be used in underwater geophysical surveys to map the seafloor and study geological features such as underwater canyons, ridges, and faults. By generating low-frequency sound waves and measuring their reflection and transmission through the water and seafloor, researchers can create detailed maps of the underwater environment and study the geological processes that shape the seafloor.
Overall, underwater infrasound projectors are a versatile tool for researchers studying the underwater environment, allowing them to study the behaviour of marine animals, monitor natural phenomena, and explore the geology and topography of the seafloor.
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seismic reflection surveys
in seismic reflection surveys, the frequency of the sound waves used depends on the depth and composition of the sediment and rock layers being studied. Generally, lower-frequency waves are used to study deeper layers, while higher-frequency waves are used to study shallower layers.
The frequency of the sound waves used in seismic reflection surveys typically ranges from 10 Hz to several kilohertz. Lower frequencies (10-200 Hz) are used to penetrate deeper into the seafloor and to study the structure of the Earth’s crust, while higher frequencies (200 Hz – several kilohertz) are used to study shallower layers, such as sediments and shallow geologic structures.
The choice of frequency also depends on the resolution required for the survey. Higher frequency waves provide better resolution and detail but are limited in their ability to penetrate deeper layers. Lower frequency waves can penetrate deeper but have lower resolution.
It’s worth noting that the use of air guns as sound sources in seismic reflection surveys can produce noise pollution in the ocean that can have negative impacts on marine life. Therefore, alternative sound sources are being developed, such as our CBASS, that produce lower-frequency sound waves and are less harmful to marine life.
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Infrasound Submarine Speakers
What we offer
We offer a range of underwater infrasound projectors that represent such a technical improvement that they are considered disruptive technology. In addition to being wider bandwidth and more powerful and reliable than other options on the market, they are smaller, lighter, and more efficient. This C-BASS family can be used for many applications, such as oceanographic, meteorological, and aquatic research. C-BASS now allows the use of infrasound for applications that were not feasible due to equipment size, weight and cost.
C-BASS M72-25
Resonance Frequency (Hz @ 20 m depth): 25
Max. Source Level (dB re 1 uPa @ 1 m): 197
Max. Depth (active compensation): >300 m. | Passive Comp: 10 m.
Diameter: 1.18 meters | Weighs 402 kg
The subaquatic C-BASS M72-25 is the most potent device on the market at this very low-frequency range.
C-BASS M72-30
Resonance Frequency (Hz @ 20 m depth): 30
Max. Source Level (dB re 1 uPa @ 1 m): 199
Max. Depth (active compensation): >300 m. | Passive Comp: 10 m.
Diameter: 1.02 meters | Weighs 355 kg
Note that dB is a logarithmic unit of measurement. A difference of 2 dB represents 60% of the sound power (watts).
C-BASS M72-40
Resonance Frequency (Hz @ 20 m depth): 40
Max. Source Level (dB re 1 uPa @ 1 m): 203
Max. Depth (active compensation): >300 m. | Passive Comp: 10 m.
Diameter: 1.18 meters | Weighs 402 kg
A difference of 6 dB represents, compared to the C-BASS M72-25, a quadrupling of the sound power (watts).
Rising Tide BioAcoustics is a worldwide authorized distributor of GeoSpectrum Technologies Inc. commercial transducers for environmental and bioacoustics applications. The products we commercialize are listed at the bottom.