![]() The time between the P- and S-waves is routinely used to determine the distance to their source, the epicenter of the earthquake. The P-wave gets progressively farther ahead of the S-wave as they travel through Earth’s crust. P-waves have speeds of 4 to 7 km/s, and S-waves correspondingly range in speed from 2 to 5 km/s, both being faster in more rigid material. Both components of earthquakes travel slower in less rigid material, such as sediments. For that reason, the speed of longitudinal or pressure waves (P-waves) in earthquakes in granite is significantly higher than the speed of transverse or shear waves (S-waves). The bulk modulus of granite is greater than its shear modulus. Earthquakes have both longitudinal and transverse components, and these travel at different speeds. Table 17.1 Speed of Sound in Various MediaĮarthquakes, essentially sound waves in Earth’s crust, are an interesting example of how the speed of sound depends on the rigidity of the medium. The relationship of the speed of sound, its frequency, and wavelength is the same as for all waves: ![]() Similar arguments hold that a large instrument creates long-wavelength sounds. So a small instrument creates short-wavelength sounds. High pitch means small wavelength, and the size of a musical instrument is directly related to the wavelengths of sound it produces. Small instruments, such as a piccolo, typically make high-pitch sounds, while large instruments, such as a tuba, typically make low-pitch sounds. The wavelength of sound is not directly sensed, but indirect evidence is found in the correlation of the size of musical instruments with their pitch. You can also directly sense the frequency of a sound. The flash of an explosion is seen well before its sound is heard, implying both that sound travels at a finite speed and that it is much slower than light. You can observe direct evidence of the speed of sound while watching a fireworks display. Sound, like all waves, travels at a certain speed and has the properties of frequency and wavelength. ![]() Sound travels more slowly than light does. It is not dependent upon the sound amplitude, frequency or wavelength.Figure 17.7 When a firework explodes, the light energy is perceived before the sound energy. rho is the density &rho and p is the sound pressure.Notice: The speed of sound is alike on a mountain top as well as at sea level with the same air temperature.Google is not correct (look at the following link): is the answer of Google: "Speed of sound at sea level = 340.29 m/s".This is no good answer, because they forgot to tell us the temperature,and the atmospheric pressure "at sea level" has no sense.The speed of sound in air is determined by the air itself. The air pressureand the density of air (air density) are proportional to each other at the same temperature.It applies always p / &rho = constant. Other speeds, such as those presented below, use values other than those relating to a "standard atmospheric day." They are not incorrect, they are simply based on values other than a "standard atmospheric day."The speed of sound is 343 m/s or 1126.547 ft/s (768.095 mph) at a temperature of 20☌ or 68☏.The speed of sound has nothing to do with the atmospheric pressure at sea level, but the temperature is very important.Scroll down to related links and read the short article "Speed of sound - temperature matters, not air pressure".The air pressure and the air density are proportional to each other at the same temperature.The speed of sound c depends on the temperature of air and not on the air pressure!The humidity of air has some negligible effect on the speed of sound. At standard day values, the speed of sound is 761 mph. The speed of sound is normally calculated using the values of a "standard atmospheric day." A "standard atmospheric day" refers to a sea level pressure of 29.92 in-Hg (1013.2 mb) and a temperature of 15☌ (59☏).
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