Sonar pulses have recently made headlines, with an incident involving Australian navy divers and a Chinese navy vessel raising concerns about the potential harm of these acoustic signals. But what exactly are sonar pulses, and how can they affect both humans and marine animals?
Sonar, short for sound navigation and ranging, is a technology that utilizes sound waves to navigate and detect objects underwater. Unlike light, which doesn’t travel as effectively through water, sound travels well due to water’s density. Sonar equipment emits short acoustic pulses and analyzes the echoes that bounce back to determine the presence of various underwater entities such as the seafloor, marine life, and other vessels.
While sonar is widely used by ships of all sizes, including commercial tankers and private boats, military sonars are generally more powerful than their civilian counterparts.
How Sonar Impacts Divers:
Studying the effects of sonar on divers is a challenging task, as intentionally subjecting individuals to harmful sound levels is ethically unacceptable. However, there have been accounts of accidental exposures and anecdotal evidence from naval personnel. Researchers have also conducted studies on human hearing capabilities underwater, both with and without the protective gear like neoprene suits, hoods, and helmets.
Human hearing underwater is not as effective as on land, but divers can still perceive sonar sounds, which are typically mid-to-high pitch noises. Exposure to naval sonars at approximately 150 decibels relative to a reference pressure of one micropascal (1 µPa) has been described by divers as ranging from “unpleasant to severe.” It is important to note that comparing sound exposure underwater to that in the air is challenging due to the significant physical differences between the two mediums.
Human tolerance limits for underwater sound exposure are estimated to be around 180 decibels relative to 1 µPa, which corresponds to being approximately 500 meters away from military sonar. At these levels, divers may experience dizziness, disorientation, temporary impacts on memory and concentration, or temporary hearing loss. The Australian divers in the recent incident sustained minor injuries, but the specific sound levels they were exposed to remain undisclosed.
With higher sound levels, closer proximity, or prolonged exposure, divers may face more severe physiological or health consequences. Extreme cases of impulsive, sudden sounds (not typical of sonar) can potentially damage tissues and organs.
The Impact on Marine Animals:
Insights into the effects of noise underwater on humans can also be drawn from studies conducted on marine animals. While most marine mammals lack outer ears, they possess inner ears similar to ours, making them susceptible to hearing damage from noise exposure. This damage can range from temporary effects, such as ringing ears or reduced sensitivity, to permanent impairment.
Marine mammals heavily rely on sound and hearing in their dark oceanic environment. They use sound for navigation, communication, hunting, and mate-finding. Toothed whales and dolphins have developed a form of biological sonar known as biosonar, which involves emitting clicks and listening for echoes. Interfering with their sounds or compromising their hearing can disrupt crucial behaviors.
It is also worth noting that non-mammalian marine fauna, including fishes, rely on acoustics rather than vision for many of their life functions. Therefore, sound disturbances may have significant implications for their survival and overall ecological balance.
In conclusion, sonar pulses serve as essential tools for underwater navigation and detection. While their impact on humans and marine life remains an ongoing area of research, it is clear that appropriate precautions and regulations are necessary to mitigate any potential harm. By further understanding the intricacies of sonar technology and its effects, we can strive for a harmonious coexistence between humans and the underwater world.
Frequently Asked Questions (FAQ)
1. Can sonar pulses cause injuries to humans?
Yes, sonar pulses can cause injuries to humans, particularly when exposed to high sound levels at close ranges or for extended periods. These injuries may range from dizziness and disorientation to temporary hearing loss and impacts on memory and concentration. Severe physiological or health consequences may occur under extreme conditions.
2. How do sonar pulses impact marine animals?
Marine animals, including marine mammals and fishes, can experience hearing damage from sonar pulses. Interference with their sounds or compromised hearing can disrupt critical behaviors such as navigation, communication, hunting, and mate-finding.
3. Is there a difference between civilian and military sonars?
Yes, military sonars are generally more powerful than civilian sonars. The increased strength of military sonars presents a higher risk for potential harm to both humans and marine life.