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Hey! I’m Ryan and we’re going to talk about sound waves: Specifically what’s called
a standing wave.
Just as every sound has a wavelength, every wavelength has a sound. So, for any given
distance, there is a sound, or frequency that fits in that length.
Standing waves are sound waves that occur when a sound is reflected off of a parallel
surface and it travels back along the same path.
The waves converge upon each other.
So what happens? The crests of the waves can meet up with the
troughs of the other wave and create what’s called a node.This is where the waves equal
each other out and there is no motion. What happens if a crest meets up with another
crest? Or a trough meeting another trough? That’s where you get maximum amplitude,
or an antinode.
The result? The original sound and the reflected sound
will combine to boost certain frequencies and to cancel others.
In a recording or mixing environment this is bad. Especially because It will change
with the size and shape of the room. And as someone who is listening to music,
you won’t be hearing what is the intended result.
So what can be done about them? Number one rule: design the room with no parallel
surfaces. Number two: Make the size of the room with
enough volume to minimize standing waves. This is easy to do when you’re building
from scratch, but not always possible. So there are other solutions.
The first is to use materials such as cloth, fiberglass, or carpet to absorb and soak up
frequencies. Some frequencies may be too much for a little
piece of cloth to handle so we also have what’s called bass traps. Which is exactly what it
sounds like. A bunch of absorptive material meant to reduce low-frequency buildup.
With all of this being said, it’s a steady balance to keep. Too much absorption will
make the room sound dead. Too little and the room will be too live.
So let’s put this into practice. Take the dorm room I’m in.
The official website says it’s 12 feet by 15 feet with a 9 foot ceiling.
To calculate, we use this equation: lambda = velocity over frequency
Where Lambda is wavelength, velocty is the speed of sound, or 1130 ft/sec, and frequency
is expressed in Hertz.
However, we need to do some simple algebra to make this equation work for us. To find
the wavelength, we need to invert the equation to become frequency = velocity over lambda.
Assume velocity = 1130 ft/sec The first distance in 12 feet. We put that
in the equation and we get 94.16 Hz The s econd is 15 feet. This gives us 75.33
Hz. For the ceiling, 9 feet gives us 125.55 Hz.
These three frequencies will give us standing waves in this room.
Alright! A little math, a little science and we’re done. Thanks for watching!.