The 7 wonders of sound
| Site: | QSC |
| Course: | House of Worship Audio Training |
| Book: | The 7 wonders of sound |
| Printed by: | Guest user |
| Date: | Thursday, 21 November 2024, 7:07 AM |
Description
Lesson Description
Learn the 7 characteristics of sound waves that shape our sonic perception so that we can manipulate them to create a pleasing sonic landscape.
Video Transcript
00:14
Sound engineering is an important skill to master in working with live sound.
00:20
While a technical understanding of how a mixer works will help you achieve the sound you’re looking for,
00:24
any seasoned engineer will tell you that the best equipment you have at your disposal is your own ears.
00:33
“Does it sound good?” can be a very relative standard,
00:36
but knowing the basic principles of how these sound waves work, and how the equipment we use can manipulate these waves,
00:43
is critical to our audio knowledge and achieving a great mix.
00:48
There are 7 characteristics or qualities that make up a sound.
00:53
Understanding these fundamental qualities can help identify and solve audio problems faster
01:00
by knowing what characteristic to compensate for and which tool to use to do so.
01:06
Think about cooking food.
01:09
Putting a meal together requires taking different ingredients and combining them together in certain ways.
01:16
If you don’t understand what the different ingredients taste like before you add them,
01:21
you have no way of knowing how they will affect the overall meal you are preparing. If something doesn’t taste right, how do you know how to fix it?
01:31
Does it need more salt? Is it too sweet? Maybe a pinch of garlic?
01:38
Understanding the characteristics of sounds is like understanding the ingredients in a meal.
01:44
So, let’s go over these characteristics and explain what role they play in making up a sound.
01:50
The first characteristic is “amplitude.” Amplitude is the relative strength of a sound wave. We might describe it as how tall a sound wave is.
02:01
The taller the sound wave, the more amplitude it has and the louder our ears perceive it to be.
02:08
We can actually measure the amplitude of a sound wave. When we do, we use a unit of measure called a Decibel.
02:17
We generally abbreviate this to “dB.” The dB unit is a very common one,
02:22
and seen all over audio equipment, so remember it. The more dB’s, the louder it will be to our ears.
02:30
The second characteristic of sound is “frequency.” Frequency is what our ears perceive as the “pitch” of a sound.
02:39
Does it sound high pitched like a flute or low pitched like a bass guitar?
02:43
We measure frequency in a unit called Hertz, and we abbreviate it to “Hz.”
02:49
You will see the Hz symbol on the EQ section of your mixer.
02:53
When we are measuring hertz, we are actually measuring how many full cycles a sound wave completes in 1 second of time.
03:01
Sometimes frequency is referred to as “Cycles Per Second” for this reason.
03:07
The more cycles per second or hertz, the higher the perceived pitch.
03:12
Here’s 100 Hz.
03:15
Here's 10,000 Hz.
03:18
The third characteristic of sound is “wavelength.”
03:22
Wavelength is the physical size of a sound wave. And yes, sound waves are really physical things.
03:29
You just don’t see them. The lower the frequency the longer the wavelength.
03:35
A 20 Hz wave has a wavelength of 56 feet for a single cycle.
03:41
A 20 kHz wave has a wavelength of .6 inches.
03:46
Because of the actual size, high frequencies are easily absorbed as they travel.
03:50
Things like walls, chairs, people, etc can easily absorb high frequencies,
03:56
whereas lower frequency waves are very difficult to absorb or control.
04:01
The fourth characteristic of sound is “velocity.” Velocity is the speed of the sound wave.
04:08
Sound travels through air at an average speed of 343 meters per second or 1125 feet per second.
04:16
That calculates to roughly 767 miles per hour.
04:22
With sound waves coming at your face at that speed all day long,
04:26
it’s no wonder you’re tired by the end of the day.
04:29
The speed of sound does vary by 2 primary things:
04:33
One is the medium it is traveling through. Like gas, liquid or solid.
04:39
Increased density means increased speed.
04:42
So, for example, sound travels faster through water.
04:47
And, number two is the air temperature. Where increased temperature equals increased speed
04:53
It's important to note that the speed of sound, while fast by car standards is still slow enough to cause trouble.
05:01
For example: Say you have an extra set of loudspeakers set up 50 ft away from the main loudspeakers in your room.
05:08
The sound waves from those loudspeakers will reach the listener’s ears
05:13
before the sound waves from the main loudspeakers at the stage.
05:18
The difference could only be milliseconds, but this will lead to a distinct lack of clarity and intelligibility
05:27
for the people listening to those loudspeakers at the back.
05:30
Don’t worry, in a later video, I’ll tell you how to solve this problem.
05:35
The fifth characteristic is “envelope.” Envelope is the lifespan of the sound wave.
05:42
Some sounds are short. They abruptly happen and then are gone; like hitting a snare drum.
05:48
while others are long and can sustain for a long period of time; like a large church bell.
05:58
Every sound wave has an attack and a decay. The attack is when the sound wave starts.
06:04
The decay is the time it takes to completed die out.
06:08
The initial attack of a sound is sometimes referred to as the “transient.”
06:13
The transient is very important to how our ears perceive the sound.
06:18
Actually if you were to remove the transients from the sound waves of different instruments
06:23
it would be very hard to tell one instrument apart from another.
06:28
The sixth characteristic is “phase.” Phase deals with the timing and shape of a sound wave.
06:34
In sound we can encounter phase issues whenever we have two microphones on a single sound source;
06:42
like drum overheads or choir mics.
06:45
If the timing between the 2 waves becomes off, they start to cancel out frequencies between them,
06:52
usually making it sound thin and sometimes very weird.
06:56
If two sound waves of the same frequency are perfectly 180 degrees out of phase
07:03
you have phase cancelation and you won’t hear either of the sound waves.
07:10
The seventh characteristic is “timbre.”
07:12
Ok, you guys, the debate on how to pronounce this word is real.
07:17
In my circles of influence, I’ve heard it most often pronounced “tamber” with a short a.
07:22
So, I’ll just go with that.
07:26
Timbre refers to the overall tonal qualities of a sound.
07:29
Many factors contribute to the timbre of a sound,
07:33
from transients to the overtones produced by the instrument or sound source.
07:38
Why does a saxophone sound like a sax and nothing like a piano?
07:44
What if they played the exact same note at the exact same loudness? We could all still tell the difference between a sax and a piano right?
07:53
I hope you said, "Yes"!
07:56
Our ears can tell the difference between a sound wave created from a vibrating wooden reed that is resonating a brass tube, like your sax,
08:04
and vibrating steel strings that has been hit with a felt hammer, like your piano.
08:10
By understanding these different characteristics of sound,
08:13
we can identify which “ingredients” in our mix needs adjusting.
08:18
Maybe something is too loud or soft. This is Amplitude.
08:23
Or one channel is too muddy or has too much bass. This would be frequency.
08:29
Or maybe the reverb time on a channel is a bit too long. An example of envelope.
08:34
Now that we know how sound waves work in their natural environment,
08:38
we’ll look at how to capture them and get them into the ears of the listener.