$sound waves diffraction corners radius wavelength$

$sound waves diffraction corners radius wavelength$

Such interference can be reduced by use of sound-absorbing materials on reflecting surfaces. In auditoriums, destructive interference between sound from the stage and sound reflected from other parts of the hall can create dead spots in which both volume and clarity of sound are poor. The interaction between the two waves produces a resultant wave. When they are out of phase, so that the compressions of one coincide with the rarefactions of the other, they tend to weaken or even cancel each other (destructive interference). When the waves are in phase so that their compressions and rarefactions coincide, they reinforce each other (constructive interference). For sound waves the phenomenon is perhaps best understood by thinking in terms of the compressions and rarefactions of the two waves as they arrive at some point. Whenever waves interact, interference occurs. Sonar is an artificial form of echolocation. A bat can unerringly locate and catch even a mosquito in total darkness. Sounds with short wavelengths are reflected even from very small objects. Bats and toothed whales emit bursts of sound of frequencies far beyond the upper limits of human hearing, as high as 200,000 Hz in the case of whales. The reflection of sound is used by some animals, notably bats and toothed whales, for echolocation-locating, and in some cases identifying, objects through the sense of hearing rather than the sense of sight. All these sound-absorbing materials are porous sound waves entering the tiny air-filled spaces bounce around in them until their energy is spent. Clothing also absorbs sound for this reason reverberation is greater in an empty hall than in one filled with people. Such problems can usually be corrected by covering reflecting surfaces with sound-absorbing materials such as draperies or acoustical tile. In a poorly designed hall, a speaker's first word may reverberate (echo repeatedly) for several seconds, so that the listeners may hear all the words of a sentence echoing at the same time. The reflection of sound can pose a serious problem in concert halls and auditoriums. (Statuary Hall of the United States Capitol is an example.) Reflection is also used to focus sound in a megaphone and when calling through cupped hands. It also accounts for the effects of so-called whispering galleries, rooms in which a word whispered at one point can be heard distinctly at some other point fairly far away, though it cannot be heard anywhere else in the room. This fact makes it possible to focus sound by means of curved reflecting surfaces in the same way that curved mirrors can be used to focus light. Sound is reflected from a surface at the same angle at which it strikes the surface. When the reflected sound is heard separately, it is called an echo. Most of the time the reflected sound is not noticed, because two identical sounds that reach the human ear less than 1/15 of a second apart cannot be distinguished as separate sounds. Sound is constantly being reflected off many different surfaces.

$sound waves diffraction corners radius wavelength$

Sound waves diffraction corners radius wavelength