Can a longitudinal sound wave be parallel of perpendicular ro the source?Why or why not?
I’m not sure I understand what you mean. Here are some possibilities: 1) By the orientation of the “sound wave”, you presumably mean one or another of the following: i) the iso-phase surfaces (the “wave fronts”); ii) the direction of the energy travel (usually perpendicular to the wave-fronts; the way they’re moving; also called the wavevector direction). 2) By the orientation of the “source”, you presumably mean one or another of the following: i) the tangent of some sort of source plane (parallel to the transducer face or something like that; probably parallel to the wave-fronts, but not necessarily depending on how the source is phased); ii) the _normal_ to the source front (more normally what one means by the “orientation of the source”; of course, this can be in different directions for a curved source). Consider a point source. It has no “direction” other than “out” (depending on the medium through which the sound goes). Wavefronts from such a source will be concentric expanding
