What is sound and how does it act within a room? This video is dedicated to giving you a very basic understanding of sound and how sound behaves. We made this video to be comprehensive and to explain in easy examples using illustrations and graphics.
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"Sound is vibrating air. Sounds simple enough, but when we try to represent that visually things can get a little confusing.
You’re probably used to seeing sound waves represented as a wavy line that resembles waves of water, but in reality sound waves are made up of areas of high and low air pressure. When we graph the pressure wave we end up with the familiar waveforms that you see in audio software.
Sound waves form from air particles colliding into each other. The body of air doesn’t move, rather energy ripples through the air particles as they push into each other.
If you look closely at your speaker while it’s playing you can see the diaphragm move back and forth to create the sound. The vibration of the diaphragm is what initially creates the alternating high and low pressure that becomes sound.
Your ear or microphone work in reverse from the speaker where the air pressure moves the diaphragm of the mic and converts it into an audio signal.
When you pluck a guitar string the string makes a small amount of sound but the vibrations from the string also vibrate the body of the guitar which propagates soundwaves in the same way the speak diaphragm does.
How are notes formed?
A musical note happens when we vibrate the air particles at a consistent frequency. If the diaphragm of the speaker pulses 55 times in one second it will produce a low A note, so the low A has a frequency of 55hz.
We can produce this note digitally with a sine wave. A sine wave is the simplest kind of sound wave as it only produces sound at the base frequency. If we look at the sine waveform we can see it fluctuates from low to high pressure at a consistent rate. This is what gives it that clean artificial sound.
Looking at a sine wave in a spectral frequency display and we can see that it’s only creating energy at one frequency, but what if we look at a square wave.
A square wave is formed by layering harmonics on top of the bass note. Hypothetically, if we layered all the harmonics up into infinity we would end up with a perfectly square shaped waveform. In reality these harmonics cut off at the audible range which is why you see small imperfections in the waveform.
Looking back at the spectral frequency display, we can see with the square wave that the base note is accompanied by several harmonics that stack at regular intervals. Sounds made in the real world tend to have this feature. When you pluck a note on a guitar string the guitar vibrates producing the bass note as well as several harmonics.
This is part of the reason why different instruments sound different when playing the same note. A sin wave is so simple it only has two discernible properties. Frequency which determines the pitch and amplitude which determines the volume of the sound.
A note played on an instrument will also have a frequency and an amplitude, but it will also have what’s called a sound envelope which is a way of describing how the musical note evolves over time.
The sound Envelope is made up of four parts. The Attack, the Decay, the Sustain and the Release.
The Attack describes the time a wave goes from zero amplitude to its maximum.
Decay is the time between the maximum amplitude to its sustained level.
The the period where the wave has
stabilized is the sustain.
The final drop form the sustain level to zero is the Release
These four properties are what give musical notes their unique timbre.
What happens when sound waves interact?
If you shine two lights across each other neither beam is affected by the other, because the light wave is the result of some kind of quantum magic, but sound waves are the result of air pressure so they combine and merge when two sounds are played in concert with each other.
When we stack the harmonics on top of eachother we no longer see the original waves. They combine to form a new shape that represents the resulting sound.
This phenomenon is known as Phase interference and it’s why it’s important to absorb the reflections in your room. Those reflections blend into the original sound meaning you’re no longer hearing the audio as intended."
3 июл 2024
