![]() Anthropogenic sounds are made by humans and stem from airplanes, cars, trains, ships, and construction sites. Biological sounds are made by animals on land, such as insects, birds, and bats, or by animals in water, such as invertebrates, fishes, and whales. Geophysical sources of sound are wind, rain, hail, breaking waves, polar ice, earthquakes, and volcanoes. 2020).Īnother way of grouping sounds is by their sources: geophysical, biological, or anthropogenic. ![]() The sound of airplanes is generated and heard in air but also transmits into water where it may be detected by aquatic fauna (e.g., Erbe et al. Sound can cross from one medium into another. In both cases, the sound is structure-borne (Dziak et al. Just as earthquakes can be felt on land, submarine earthquakes can be sensed by benthic organisms on the seafloor. Some of the sound may have traveled as a structural vibration through the ground and is therefore referred to as structure-borne. Those looking at the effects of marine seismic survey noise on baleen whales work with water-borne sounds. For example, scientists studying bat echolocation work with air-borne sound. One way is to label sounds according to the medium in which they have traveled: air-borne, water-borne, or structure-borne (also called substrate-borne or ground-borne). There are many ways to describe, quantify, and classify sounds. In contrast to noise, a signal is wanted, because it conveys information. It could be the recorder’s electric self-noise (see also American National Standards Institute 2013 International Organization for Standardization 2017). It could be the ambient noise at a recording site and encompass sound from a multitude of sources near and far. Noise could be the sound near an airport that has the potential to mask speech. One person’s music is another person’s noise. Different listeners might perceive sound differently and classify different sound as noise. Whether a sound is perceived as noise depends on the listener, the situation, as well as acquired cognitive and emotional experiences with that sound. It therefore requires a listener and includes an aspect of perception. Noise is also sound, but typically considered unwanted. As well, the effects of ultrasound on humans have been of concern (Parrack 1966 Acton 1974 Leighton 2018). For example, infrasound from wind turbines has been linked to nausea and other symptoms in humans (Tonin 2018). Also, inaudible doesn’t mean that the sound cannot cause an effect. For example, dolphins hear well into high ultrasonic frequencies above 100 kHz. While sound outside of the human hearing range is inaudible to humans, it may be audible to certain animals. ![]() These definitions are based on the human hearing range of 20 Hz – 20 kHz (American National Standards Institute 2013). For example, ultrasound refers to sound at frequencies above 20 kHz, while infrasound refers to frequencies below 20 Hz. Not all sounds produce an auditory sensation in humans. Sound can also be defined as an auditory sensation that is evoked by such oscillation (American National Standards Institute 2013), however, more general definitions do not require a human listener, do allow for an animal receiver, or don’t require a receiver at all. The more scientific definition of sound refers to an oscillation in pressure and particle displacement that propagates through an acoustic medium (American National Standards Institute 2013 International Organization for Standardization 2017). ![]() Acoustics is the science of sound and includes the generation, propagation, reception, and effects of sound. The sound then travels from the source through the air to our ears. ![]() There has to be a source of sound, such as another person, an animal, or a train. Most people think of sound as something they can hear, such as speech, music, bird song, or noise from an overflying airplane. ![]()
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