But the music from all instruments arrives in cadence independent of distance, and so all frequencies must travel at nearly the same speed. Suppose that high-frequency sounds traveled faster-then the farther you were from the band, the more the sound from the low-pitch instruments would lag that from the high-pitch ones. The purple line with peaks of the same height are from the interference of the waves from two slits the blue line with one big hump in the middle is the diffraction of waves from within one slit and the thick red line is the product of the two, which is the pattern observed on the screen. If this independence were not true, you would certainly notice it for music played by a marching band in a football stadium, for example. Figure 4.11 Diffraction from a double slit. This independence is certainly true in open air for sounds in the audible range of 20 to 20,000 Hz. One of the more important properties of sound is that its speed is nearly independent of frequency. The time for the echo to return is directly proportional to the distance. A bat uses sound echoes to find its way about and to catch prey. Figure 3 shows a use of the speed of sound by a bat to sense distances. \boldsymbolit is 343 m/s, less than a 4% increase. And Diffraction is more in longer wavelength waves, as is less in wider slits. Because Light Wavelength is actually less than a sound wave. The relationship of the speed of sound, its frequency, and wavelength is the same as for all waves: By contrast the wavelength of light is around half a micron, so you need to get the size down to the micron scale before light starts scattering strongly. 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. When a firework explodes, the light energy is perceived before the sound energy. Describe the effects of temperature on the speed of sound.įigure 1.Describe the effects on the speed of sound as it travels through various media.Describe the relationship between the speed of sound, its frequency, and its wavelength.