Thanks, but not the same theory I wrote about some time ago.
I should keep notes - searching past posts is such a tedious task!
I should keep notes - searching past posts is such a tedious task!
Regards diffraction at baffle edges, that can be almost eliminated. A narrow straight edged baffle puts the diffraction close to the driver so diffractions blend with it. A wide baffle reflects so could spoil the imaging for some people.
No, it was a rather off-piste theory that postulated that sound was not propagated by waves, but by particles. The name given to those particles currently eludes me.
I'm not talking about vibration of the particles of the medium, I am talking about sound itself consisting of particles!
However, as I don't recall that rather sensational theory, there's no point in discussing the matter further.
What I really mean is that it is a load of bunkum!
However, as I don't recall that rather sensational theory, there's no point in discussing the matter further.
What I really mean is that it is a load of bunkum!
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Gotcha, it was probably a theory to explain an observation, apparently sometimes it's useful to describe matter as behaving like a wave.
How does an air molecule at the wavefront pass it's energy to molecules around it? I can't imagine it being only in one direction.
How does an air molecule at the wavefront pass it's energy to molecules around it? I can't imagine it being only in one direction.
I'm not sure what your direction of questioning is, but first of all let's define a wavefront.
A wave front is an imaginary surface drawn through all the points of a wave that vibrate in unison i.e. in phase. This applies to both transverse waves like light, and longitudinal waves like sound.
When sound travels through air, the molecules of the air simply vibrate to and fro along the direction of energy propagation. Each molecule vibrates slightly out of phase with its neighbour, resulting in the compressions and rarefactions of air particles by which energy is transferred in a longitudinal wave.
A longitudinal wave will propagate in all directions from a point source via the vibrations of the air molecules.
A wave front is an imaginary surface drawn through all the points of a wave that vibrate in unison i.e. in phase. This applies to both transverse waves like light, and longitudinal waves like sound.
When sound travels through air, the molecules of the air simply vibrate to and fro along the direction of energy propagation. Each molecule vibrates slightly out of phase with its neighbour, resulting in the compressions and rarefactions of air particles by which energy is transferred in a longitudinal wave.
A longitudinal wave will propagate in all directions from a point source via the vibrations of the air molecules.
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When that is depicted in an animation it's usually bounded at the sides in some way as if each molecule only effects the next molecule in the direct path/angle of the wave's direction of propagation.
Ripple tank and graphic presentations of sound "waves" are just 2-dimensional. In real world sound propagates/expands 3-dimensionally from the source (typically a pointsource, but it's relative to wavelength/driver diameter).
When an ear or a microphone is used to detect sound signal/pressure variations, it "sees" a 2-dimensional phenomen - pressure variations at that spot. This is how and what what we typically measure with loudspeaker design and evaluation
Sound_Propagation
http://assets.press.princeton.edu/chapters/s9912.pdf
When an ear or a microphone is used to detect sound signal/pressure variations, it "sees" a 2-dimensional phenomen - pressure variations at that spot. This is how and what what we typically measure with loudspeaker design and evaluation
Sound_Propagation
http://assets.press.princeton.edu/chapters/s9912.pdf
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Those show the effect on pressure which is useful as it's the result of the molecules interacting. A line source would show what's happening at the edge of the wavefront, one could infer why, but does that show the physics of what's happening in reality?
Isn't it the case that each molecule is only reacting to the motion of it's "immediate" neighbours?
Isn't it the case that each molecule is only reacting to the motion of it's "immediate" neighbours?
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Physics is but an interpretation of reality, and frequently a poor one at that!
So it will forever be merely an academic question? I wonder what answer Charlie will chose to believe.
Troels Gravesen presented an interesting article on wide baffled speakers in relation to the baffle step phenomenon here: www.troelsgravesen.dk/Acapella_WB.htm. It deals more with the practical rather than the theoretical aspects of baffle step as applied to loudspeaker construction.
I personally have struggled with the practical aspects of baffle step in trying to determine at what point does one need to be concerned about it when designing and building a loudspeaker. I understand that a free-standing loudspeaker with a narrow baffle that is positioned well out into a room's space will require more correction than a wide-baffled speaker and that one positioned against a wall will require perhaps none at all, but how does one quantify the baffle step phenomenon reliably? In other words, how wide does the baffle need to be and/or how close to a wall behind or to the side does it need to be to eliminate the need for baffle step correction?
I personally have struggled with the practical aspects of baffle step in trying to determine at what point does one need to be concerned about it when designing and building a loudspeaker. I understand that a free-standing loudspeaker with a narrow baffle that is positioned well out into a room's space will require more correction than a wide-baffled speaker and that one positioned against a wall will require perhaps none at all, but how does one quantify the baffle step phenomenon reliably? In other words, how wide does the baffle need to be and/or how close to a wall behind or to the side does it need to be to eliminate the need for baffle step correction?