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Looper's Delight
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Matthias and also Tim already said some things regarding this topic, so I'll only add what hasn't been said before: The directional characteristics are a property of the source (or sink). This property of the source or sink is usually dependant on the frequency, but the directional characteristics are not a property of the sound wave or its frequency. A directional source (like a dynamic speaker) tends to become omnidirectional if the wavelength of the waves reproduced considerably exceeds the dimensions of the source (rule of thumb here). The wavelength is the phase velocity (the velocity with which the wave distributes, here "the speed of sound") divided by the frequency. That means, with a phase velocity of ~300m/s and our speaker a diameter of 0.3m, we get f=1000Hz or a frequency of around 100Hz where the wavelength exceeds the speaker dimensions considerably. Yet, if we reproduced this same 100Hz wave with a speaker a diameter of thirty meters, this speaker would be directional all right... The same is true for the sink (in this case: your head): if the wavelengths considerably exceed the dimension of your head, then it becomes harder to make out the direction a sound comes from from the difference in sound pressure level received by both ears. If a tone of a sufficiently high frequency comes directly from the right side of your head, then the perceived sound level in your right ear is much higher than in your left ear because your head shields your left ear from the directed sound wave. Note that there are other effects you can use to make out from which direction sound comes: decrease in intensity with distance travelled and delay from distance travelled. Actually, two standard stereo miking techniques make use of either the level difference by the directionality of your ears (X/Y, coincident miking) or of the delay (A/B, spaced pair) exclusively and in an exaggerated way. Still, you can perceive the direction sound comes from even for extremely low frequencies, although this only works for very high sound pressure levels. During thunderstorms, you sometimes feel the very low frequency components with your body and are able to make out a direction. There has been some confusion going on about this topic in recent years, caused by companies who try to tell you that you can get "cinema" sound with a sub and a set of miniature sattelites with xover frequencies of 130Hz, 180Hz or even higher. If you do however look up the specs for Dolby Digital, you'll find that while the LFE (which stands for "low frequency effects" and is to be used for the "big bangs" of planes exploding or atomic bombs going off exclusively) channel has a frequency range of 3-120 Hz, the remaining five (or more for the EX format) front, center and surround channels have a specified frequency range of 3-20000 Hz. --- Travis Hartnett <travishartnett@gmail.com> wrote: > Maybe I'm just weird, but I've never found bass to omnidirectional. > Less directional than higher frequencies, okay, but > it takes a lot > less than a gun to my head to figure out where the > bass is coming from > when I see a band play. __________________________________________________ Do You Yahoo!? Tired of spam? Yahoo! Mail has the best spam protection around http://mail.yahoo.com