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 It's Studio Microphone Month at Sweetwater!
It's Studio Microphone Month at Sweetwater!
This month we're celebrating one of the most important pieces of your studio, the microphone! We're giving away a Neuman BCM 104 AND we've updated our online Microphone Department making it easier than ever before to find the microphone you've always dreamed of. Plus, if you're new to microphones, be sure to check out our Microphone Buying Guide where you'll learn about the differences in diaphragm sizes, what a polar pattern is and a whole lot more.
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| Propagation |
In physics, the motion of waves through or along a medium. A "wave" can be sound, electromagnetic, electrical or other type. The concept can even be applied to the motion of an earthquake. A "medium" can be air, a gas, a liquid or a solid. In the case of electromagnetic waves, propagation may occur in a vacuum as well as in material media.
Sound is made up of waves, which are created by vibrating objects and propagated through a medium (normally, the air) from its source to a listener.
It's important to understand that propagation does not mean the wave "travels" through the medium in the manner that you travel from one point to another. A good way to visualize this is to imagine a crowd in a stadium doing, uh... "The wave." The person who starts the wave does not travel the length of the stadium to the other end. Instead, he sets the wave in motion, which is picked up by the next person, who transfers it to the next, and so on. After moving, each person (depending on the level of beer consumption) returns to an "at rest" state. The same is true of sound waves: each air molecule is charged with energy and set into motion, which is then transferred to the next molecule, and ultimately to the molecules nearest to your ear. |
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| Clearing the Air About Sound Waves |
Q: "Does sound really travel the way that graphs and images in books indicate?"
A: We see graphs of wave forms in print so much that it's easy to start thinking of sound as a two-dimensional, linear occurrence. Most often we see a plot that represents the motion of a vibrating string, which also happens to be a depiction of a sine wave. It could be misinterpreted to imply that the sound moves directionally from left to right. Even when we use the "ripples on a pond" visual example we aren't accurately depicting sound wave propagation.
In fact, sound waves generally move in a spherical pattern, in all directions, including vertically. If you're in doubt, climb a tree and note that you can still hear the sound of everything happening on the ground. In some cases steps can be taken to restrict the directionality, such as with a horn, but most sounds will "naturally" seek to disperse in all directions unless otherwise acted upon.
As a pressure wave moves through an increasingly larger space, it does change. First of all, as the energy of the wave is dispersed along an ever-expanding front, it diminishes accordingly until ultimately there is not enough energy to generate further sound. This is a consistent, measurable occurrence - if we consider loss of energy in terms of loudness, the sound pressure level (SPL) drops by approximately 6dB each time the distance from the source doubles if the sound is dispersing in a free space. In other circumstances the losses are less.
Second, the waveform (which is almost always much more complex than the simple sine wave we often use for reference) begins to be reshaped by merging with additional waves in the space. These can be from other instruments, wind noise, voices, machines - anything else that produces a sound. |
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