Finally, it discusses bone conduction, a mechanism of audition significant in aquatic sound reception. It also examines sound localization, the mechanism used to determine the direction of a sound source. It then describes acoustic impedance, the intrinsic resistance of a substrate or of a mechanism against transmitting sounds. It first discusses sound detection through sound frequency, wavelength, and amplitude. It describes the different aspects of sound, the ability of air and water to transmit sounds, and the opportunities and challenges that living in the two media presents to the organism. Most animals are only sensitive to frequencies above the human range.This chapter analyzes the physics of sound and hearing in water and air. In science and technology, we can also use ultrasound for imaging processes in non-destructive testing procedures, such as acoustic microscopy. These applications range mainly from 1 to 3 MHz, but we can even find frequencies up to 7.5 MHz. Ultrasound waves also have applications in therapeutic procedures, and cancer therapy is one of the more promising areas. When a sound wave strikes the targeted object, it bounces back, and with these echoes, physicians construct images of the organs. Have you heard the term "ultrasound imaging" and don't know why it's called that way? Ultrasound imaging uses ultrasound waves to obtain images of the body's internal organs, which can be used, for example, to calculate the volume of your bladder. Curiously, some animals can perceive this range of sound waves, which is why elephants flee in fear when earthquake events are about to occur. Some natural phenomena also emit infrasound, such as volcanic eruptions (below 20 Hz) and earthquakes (below 10 Hz). They use these signals to communicate over distances up to 10 km. Also, sound waves can behave as longitudinal and transversal when the medium is a solid material.Īs you may imagine, the study of sound waves is mainly concerned with how it propagates through that strange fluid called air, as that's how we usually receive sound.Īlthough we believe we can hear all the sounds emitted by elephants, most of the sounds produced by these animals are low-frequency noises below 20 Hz, known as infrasound. Longitudinal waves are the most relevant in our daily lives as they are present a long as a fluid acts as the propagation medium. The most common example of this type is sea waves. Combined waves: These are a combination of longitudinal and transversal waves.
Transverse waves: The particles move back and forth transversely (at right angles) to the wave motion.Longitudinal waves: Each particle moves back and forth in the same direction as the wave.Mechanical waves are classified into three groups, depending on the direction of the periodic motion relative to the movement of the wave: Examples of electromagnetic waves are light, microwaves, and radio waves. Sound is an example of a mechanical wave, and other examples include ripples on the water's surface, seismic shear waves, and water waves. The main difference is that mechanical waves need a medium to travel (a material), whereas electromagnetic waves can travel through a vacuum. There are two main kinds of waves: mechanical waves and electromagnetic waves. Waves occur when there's a disturbance in a system, and that disturbance travels from one place to another. Waves are everywhere and manifest in different ways.
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