Amplitude is the term we use when were talking about level. The vertical axis that you see on the right side of the spectrum shows the level or amplitude of a signal. A lower amplitude will be heard is quieter than a higher amplitude.
When were using an EQ to add amplitude and a certain frequency area, that's generally referred to as a boost. When we remove amplitude we call that a cut. You'll be practicing boots and cuts at different frequency points when you use the EQ practice tool.
The unit we use to describe amplitude is called the decibel or dB. Take a look at the meter on the right. You see a signal that sitting at -5 dBFS. Now I'm going to open up a fader like what you see in your DAW, and I'm going to turn the signal up, by 2 dB on the fader. If we look back at the meter, we now have a level of -3 dBFS. Let's go back to the fader. Now I will bring the signals down 3 dB, and you'll see that change reflected on the meter.
That's something that might confuse you is that the number zero exist in two places you'll see it on the fader, and you'll see it on the meter. So we need to break this down to explain it a little better.
0 on the fader means "No change". Sometimes we call it "Unity Gain". So when a signal is coming into the fader if it sits at 0, it won't change look at the same reading on your meter. Now let's take a look at the meter. The 0 here is something called 0 dBFS, which is "Full Scale". That's telling us the maximum allowable signal level, before we quit or go into distortion. So whatever we do with our fader to turn off signal up or down, we need to look at our meter and make sure that we don't turn it up so much that the signal crosses above 0. So 0 dBFS is the maximum level you can have without clipping. We described signal relative to that, so a signal that's it and -3 dBFS would be 3 dBFS below the maximum of 0.
You also need to understand the difference between peak level, and what is sometimes called RMS or average level.
Peak level is the absolute level of a signal at a given instant in time. Looking at the waveform for this song, we can visually see the highest peaks.
RMS level is an average of levels over time. A recording can be measured in terms of RMS or average level, as well as peak level.
What's important about peak level is it tells us how close are signal or a recording is to distortion. What's important about RMS level is it's connected to how we hear. So when we look at the RMS or average level, it tells us something about the perceived loudness, whether it's what instrument compared to another in a mix, or the overall sound coming from the speakers compared to what we see on a meter, when we're mastering.
We'll talk more about loudness, when we get into compression, but one thing I want to mention here is we don't really use the word volume when we talk about level, that's more about measuring gases and liquids. We usually like to talk about level and perceived loudness.
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