freddofrog
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No, air "vibrates" at a frequency (or spectra of frequencues). If you take one frequency, it's easier to explain.
A vibrating guitar string vibrates "transversely" which means that the vibration is at right-angles to the direction of the energy travel (and light is a transverse wave as well).
However sound is a "longitudinal" wave, which is actually easier to consider, because the vibration is in the same direction as the energy travel. In effect, for a single frequency set up as a "standing wave", the vibration constists of air at slightly higher densities and slightly lower densities spread out in the air space, with one higher density and one lower density region in the wavelength of the frequency.
This is what you will get from one loudspeaker. If you place another loudspeaker next to it, then if it is wired in anti-phase, the lower density regions over lap with the higher density regions from the other speaker, and vice versa, so they cancel one another out. Obviously the two centres of excitation are not at the same point, so they cannot totally cancel out.
As you move the speakers further apart, the cancellation pattern starts to change, depending on the resonance of the air space. Two speakers wired anti-phase opposite one another in car doors, will produce a very different pattern of vibration in comparison to when wired in-phase. In-phase will basically resonate the air-space more efficiently than anti-phase.
A vibrating guitar string vibrates "transversely" which means that the vibration is at right-angles to the direction of the energy travel (and light is a transverse wave as well).
However sound is a "longitudinal" wave, which is actually easier to consider, because the vibration is in the same direction as the energy travel. In effect, for a single frequency set up as a "standing wave", the vibration constists of air at slightly higher densities and slightly lower densities spread out in the air space, with one higher density and one lower density region in the wavelength of the frequency.
This is what you will get from one loudspeaker. If you place another loudspeaker next to it, then if it is wired in anti-phase, the lower density regions over lap with the higher density regions from the other speaker, and vice versa, so they cancel one another out. Obviously the two centres of excitation are not at the same point, so they cannot totally cancel out.
As you move the speakers further apart, the cancellation pattern starts to change, depending on the resonance of the air space. Two speakers wired anti-phase opposite one another in car doors, will produce a very different pattern of vibration in comparison to when wired in-phase. In-phase will basically resonate the air-space more efficiently than anti-phase.
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