Sound 3 Flashcards
In which direction is sound reflected as it strikes a surface?
Sound is reflected from a surface at the same angle at which it strikes the surface. 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. 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.
What is Reflection ( of sound)?
Sound is constantly being reflected off many different surfaces. 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. When the reflected sound is heard separately, it is called an echo.
How can Reflection of sound be stopped?
by covering reflecting surfaces with sound-absorbing materials such as draperies or acoustical tile. Clothing also absorbs sound; for this reason reverberation is greater in an empty hall than in one filled with people.
How does sound absorbing material work?
sound-absorbing materials (such as draperies) are porous; sound waves entering the tiny air-filled spaces bounce around in them until their energy is spent. They are, in effect, trapped.
What is Refraction of sound?
When a wave passes from one material to another at an angle, it usually changes speed, causing the wave front to bend.
What is Difraction?
When sound waves pass around
an obstacle or through an opening in an obstacle, the edge of the obstacle or the opening acts as a secondary sound source, sending out waves of the same frequency and wavelength (but of lower intensity) as the original source. The spreading out of sound waves from the secondary source is called __________. Because of this phenomenon, sound can be heard around corners despite the fact that sound waves generally travel in a straight line.
What is Interference (of sound)?
Whenever waves interact, interference occurs. 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. When the waves are in phase so that their compressions and rarefactions coincide, they reinforce each other (constructive interference). 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). The interaction between the two waves produces a resultant wave
What is a Beat?
Interference between two waves of nearly but not quite equal frequencies produces a tone of alternately increasing and decreasing intensity, because the two waves continually fall in and out of phase. The pulsations heard are called BEATS. Piano tuners make use of this effect, adjusting the tone of a string against that of a standard tuning fork until beats can no longer be heard.
