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Creating the illusion of distance & moving sources outdoors

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Creating the illusion of distance & moving sources outdoors

Postby Anonymous » Sat Mar 10, 2012 12:11 am

Hello, I've been recording stuff outdoors, but for some trickier parts (such as those that require closer mic'ing) I might need to recreate the effect of instruments played in an open wide expanse like moorland, so that instruments sound far away, change as they move around, become obscured by atmospheric sounds, etc.

I'm wondering the best way to go about this. What should I study/understand about acoustics? I understand that higher frequencies become less apparent with distance (because they run out of energy quicker), but is this a proportionate change? Perhaps there's software that can affect this better than I could ever do manually?

Kind Regards,

José
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Re: Creating the illusion of distance & moving sources outdoors

Postby ef37a » Sat Mar 10, 2012 6:55 am

“Distance of the sound source
The human auditory system has only limited possibilities to determine the distance of a sound source. In the close-up-range there are some indications for distance determination, such as extreme level differences (e.g. when whispering into one ear) or specific pinna resonances in the close-up range.
The auditory system uses these clues to estimate the distance to a sound source:
• Sound spectrum : High frequencies are more quickly damped by the air than low frequencies. Therefore a distant sound source sounds more muffled than a close one, because the high frequencies are attenuated. For sound with a known spectrum (e.g. speech) the distance can be estimated roughly with the help of the perceived sound.
• Loudness: Distant sound sources have a lower loudness than close ones. This aspect can be evaluated especially for well-known sound sources (e.g. known speakers).
• Movement: Similar to the visual system there is also the phenomenon of motion parallax in acoustical perception. For a moving listener nearby sound sources are passing faster than distant sound sources.
• Reflections: In enclosed rooms two types of sound are arriving at a listener: The direct sound arrives at the listener's ears without being reflected at a wall. Reflected sound has been reflected at least one time at a wall before arriving at the listener. The ratio between direct sound and reflected sound can give an indication about the distance of the sound source.” From Wiki/Google.
Then too outside sources are completely “dry”, devoid of any reverberation (unless you want to simulate a large reflecting object. Note too that we retain the ability to localize sources down to very low frequencies outdoors, ‘tis only the “mess” inside a building that prevents us doing this.
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Re: Creating the illusion of distance & moving sources outdoors

Postby Jack Ruston » Sat Mar 10, 2012 10:17 am

In an open moorland for example, there are very few or no early reflections. So you'd need to record your source material in an environment with that in mind. The moment you hear early reflections your brain will interpret an acoustic space which you're trying to remove.

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Re: Creating the illusion of distance & moving sources outdoors

Postby Hugh Robjohns » Sat Mar 10, 2012 12:54 pm

As jack says, to be convincing you need to record in a really, really dead environment. Any hint of early reflections destroys the illusion immediately. You also need to lose some of the top end, as has been said, and also a fair bit of the bottom end too. These two aspects are down to sound wave propagation.

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Re: Creating the illusion of distance & moving sources outdoors

Postby Martin Walker » Sat Mar 10, 2012 2:49 pm

And if you want to spice things up a bit remember that any natural air movement outside (i.e. gusts of wind) will result in cyclic level fades as well as top-end changes, rather like a very large and extremely slow-spinning Leslie speaker


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Re: Creating the illusion of distance & moving sources outdoors

Postby Guest » Sat Mar 10, 2012 3:41 pm

Thanks for that.
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