what do is meant by sound barrier?
597670
doesn't really exist.  Commonly referred to as MACH.  As you approach Mach the air has trouble getting out of the way fast enough.  This creates a pressure build up.  (why modern jets have swept wings) Once exceeded the jet creates a sonic boom.  \n\nThe sound is still created, but it can't keep up with the source. Try to find a jet by sound alone.  Then find it visually.  It's kinda hard.  Even if directly overhead.
29871
60 dB sound pressure level is about the level of an ordinary conversation.  See source for more info.
577560
http://en.wikipedia.org/wiki/Sound_waves
856862
because it may have pop up blocker, when it blocks pop up a click sound can be heard
84345
Think of an airplane as a boat for a moment. You know that a fast-moving boat causes a wake to form behind it. Well, an airplane does this with sound waves. Sound waves propogate ahead of an airplane if it is going slower than the speed of sound. However, if an airplane breaks the sound barrier, the sound waves are pushed together. At first, you hear nothing, and then you hear the sonic boom (the "wake" of the airplane).
104416
It looks like diffusion. \nSound waves are reflected between parallel lines so that the mulitple reflections makes sound waves diffuse from one point to other. This is the best logical explaination i can think of. But additional info on this question can help to explain further.
654732
Sound is a form of energy which is audible that is it can be registered by the ear. It travels in a medium and cannot travel in vaccuum. It is propagated in air as a series of compression and rarefaction (or expansion zones) these zones exist along the line joining the source and observer.\n\nIt is hard to localise sound unlike light because sound travels due to the disturbance of the material particles themselves.\n\nSound travels faster in a denser medium.
356537
They do.\n\n(It bears mentioning at this point that there is such a thing as subsonic ammunition.)\n\nWhen something moves through the sound barrier (accelerates to beyond the speed of sound,) it creates a conical pressure wave that travels some distance behind.  The distance increases between the object and the face of tis pressure wave increases as velocity increases.\n\nThe size of this pressure wave is roughly governed by the size of the object.  Therefore, aircraft make very loud "sonic booms" whereas bullets tend to make a slight popping-whining sound as they travel past you.\n\nThe noise is, believe me, rather unnerving.
997346
See this all depends.... if this were in the philosophy section, then it could be debatable.  But alas- it's in the botany section, so yes- it does make a sound.  Friction is created as it falls through the air and hits the ground, and that friction causes soundwaves.  Whether someone is there or not is irrelevant.  Humans can only pick up on a certain range of decibels anyways.  That doesn't mean just because we can't hear it, it doens't make a sound.  It just means that we can't hear it.  People need to get unstuck from themselves and think outside the human box.  "If humans can't.... must not be possible."  Meh.
296243
There are materials like curtains, sofa, cushion,etc which absorb sound are used . Rough finished and curved walls with wooden materials will absorb sound.Civil engineers know well about the materials and design the building acordingly.
20017
Popup stopper uses that sound to let you know that a popup has been blocked..do you have Popup Stopper?..if so you can have that sound disabled in the options menu...I used that software years ago and remember it making that sound and driving me nuts..Steve
362546
Sound is a pressure wave. When it hits a surface the pressure wave is sensed as a force wave. Although weight is a force, the force caused by sound is not weight since it is continuously varying about a mean of zero.
510408
As many sounds as you can hear.  Some people are hard of hearing on high or low sounds.
394921
Sound does not travel in a vacuum.
815455
blocked pores and bacteria.
158439
if you listen to tape sound transmission is through air only. \nIf you listen to yourself, sound transmission is through air AND through your bones (vibrations of your vocal chords can travel in your body). \nTry talking under water (do not breath in while doing that...) and it will sound very different again.
364559
I'm going to assume that you are asking which of the two materials you listed are best at absorbing sound vibrations.  There are many methods, the two you listed are valid, albeit a bit primitive, but the link that I have included below may help you much more.  (Cork soundproofing can be quite expensive, btw.)