americanforest said:Ok then, I can generalize my questions and ask why do low frequency waves pass through matter and high frequency waves are not able to?
americanforest said:A strange question that I recently thought of. Both sound and light are waves so why is it that I can hear through walls and around corners but can't "see" through walls and around corners?
americanforest said:Here's another sound related question : If I am in the desert (or any barren, flat, place with air to propagate through) and my friend is standing miles and miles away with some kind of GPS system so I can look directly at him, can I shout and have him hear me, assuming there is nothing in the way. As far as I can tell, the problem with getting sound waves a certain distance is one of avoiding refraction and reflection.
What you are describing here is the frequency dependent attenuation due to absorption losses. This is a relatively weak effect compared to the geometric power reduction with distance (inverse square for a point source, linear inverse for a line source, etc.).ranger said:The further you are from the source of the sound, the longer are its wave lengths with a lower frequency. Do you know how the frequency of the wave affects our ability to hear?
Gokul43201 said:What you are describing here is the frequency dependent attenuation due to absorption losses. This is a relatively weak effect compared to the geometric power reduction with distance (inverse square for a point source, linear inverse for a line source, etc.).
The important point here is that the sound intensity level decreases with distance from the source. When the intensity level falls below the minimum detection threshold for a human ear, the sound will no longer be heard by the average human being.
Light and sound are completely different things. The reasons why radio waves pass through walls is different from why sound waves are transmitted through walls (read that wording carefully!).pivoxa15 said:You are thinking low freq = sound. high freq = light. But you must first understand that light and sound are fundalmentally two different waves. LIght is an electromagnetic wave and sound is a longitudanal wave due to longitudanal oscillations of particles in the medium in which sound exists hence a mechanical wave.
Neither light nor sound necessarily propagate in circles (and they aren't fields themselves). A laser or even a good flashlight does not and sound from a trumpet (for example) is also highly directional, as, of course, is sound transmitted through a rod.americanforest said:This leads to another question which is not really related at all to this conversation: do all fields propagate out in circles like this, thus explaining the inverse square dependency (at least for electricity and gravity, the two I have studied so far)?
This is true for a gravitational field and electric field. You can say the field is radially symmetric.This leads to another question which is not really related at all to this conversation: do all fields propagate out in circles like this, thus explaining the inverse square dependency (at least for electricity and gravity, the two I have studied so far)?
This is close, but not correct. Actually, the energy from a point source radiates outwards so that all the energy emitted during an interval [itex]\delta t[/itex] is, at some subsequent time t, spread over a spherical shell of radius r=ct (where c is the speed of propagation of the energy, assuming all the energy propagates at the same speed) and thickness [itex]\delta r=c \delta t[/itex]. The volume of this spherical shell is given by the product of the thickness and the surface area, [itex]\delta V = 4 \pi r^2 \delta r[/itex]. Energy conservation then leads us to the result that [itex]I(r) \cdot 4 \pi r^2\delta r = constant[/itex]. Thus, the origin of the inverse square power dissipation from a point source is due to the surface area of a sphere being proportional to [itex]r^2[/itex].americanforest said:I think I understand what you're saying, and I think it helped me understand something else, this inverse square rule that seems to pop up all over the place. Looking at this http://hyperphysics.phy-astr.gsu.edu/hbase/sound/imgsou/rwave2.gif" I realized that the energy(or whatever quantity) of the sound in this case starts our propagating in a small circle whose radius gets bigger and bigger, eventually the same energy (??) has to fill a much bigger circle's area and so is obviously weaker at any given point on the level curve. Since the area of a circle is ~r^2 this helps me understand all the ~r^2 rules popping up in Electricity, Gravity, who field strength decreases the same way.