The Art & Science of Audio & Video

What is Sound?

Physiologically, sound is a vibration in a medium once received by the ear. To achieve this you need three key elements.
1. a sound source
2. a medium for the sound to travel through
3. an ear to detect the sound

In the physical realm sound is a disturbance that creates the sensation of sound. By definition sound is a simple form of energy. When there is a series of disturbances in a medium, such as variations in pressure and alternations in direction of molecular movement the ear interprets that as sound. Sound is objective and therefore exists by definition regardless if there is any living thing to interpret it or be affected by it. So the answer to the old adage, “If a tree fell in the forest and no one was there to hear it would it make a sound?” is yes it would make a sound.

Most of us typically associate sound being transmitted through the air, the air being the “medium”. However the medium can also be solids (metal, wood, and rock), liquids or gases. How do we produce sound? Imagine one of the coiled spring door stops screwed into the base boards behind the doors in your house. Flick the door stop and in begins vibrating back and forth at a rapid pace, this is known as oscillation. This action creates a disturbance in the air molecules around it which are transmitted by creating alternating pressure waves in the form of compressed and rarified air that propagates away from the sound source, in this case the door stop. Should you designate one side of the doorstop (+) positive and the other (-) negative the movement would represent the changing cycle of (+) or (-) potential in reference to (0) which would be the doorstop at its’ resting position.

Now more specifically Acoustic energy is the total energy of any given medium minus the energy it would poses in a state of rest. Vibration refers to the oscillating motion of the media that does not necessarily produce the phenomenon of “sound” to a human ear. Vibration typically will refer to the non audible acoustic phenomena more commonly know as the experience of touch or feeling. However, there is no fundamental difference between the sonic and vibratory forms of energy with the exception that one is not perceived as “sound” to the human ear.

Here are some helpful bits of information concerning sound. Sound travels very fast but is like comparing a Vespa and a F1 race car in comparison to the speed of light. The speed of sound is affected greatly in air by temperature, humidity and wind. In water which is denser than air is approximately 4757 feet/second or four times faster. In steel the speed may reach 16,500 feet/second which is about 15 times faster than in air.

This of course is the cliff notes version of what “sound” truly represents from the viewpoint of a traditional acoustician. However I believe it is a start at establishing some ground work from which we will be building on for the next few weeks.

by Jason Levert May 10th, 2008


June 10, 2008 - Posted by | Class: E=MC2(+/-3db) | , , , , , , ,

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