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I want to tell you a little bit about sound. The goal here is to give you some fundamental information that will help you as you record, edit and mix audio in Soundbooth. Vibrations create sound. For example, your vocal cords vibrate, out comes sound. Sound can travel through solid objects, or through liquid, but mostly sound is moving air molecules. Those moving molecules behave sort of like waves. Let me show you what I mean. So here we are in Soundbooth, and I have loaded up the file called a440-octaves-tone, which is inside the a440 subfolder inside your Exercises Folder.
Now I'm looking at the soundwave, which I can explain how you look at these soundwaves in other tutorials, but right now, I just want to demonstrate how soundwaves look. This tone is a very simple tone. It's called a440 because it's 440 cycles per second. It's a standard tuning tone used by orchestras and instruments, things like that. Listen to it for a second. (Tone playing.) You've probably heard that tone before. It's the A above middle C, if you know your music, and it has 440 cycles or waves per second. Now the top of this cycle is when that's the most pressure being applied against your eardrum and the bottom here is when the pressure is released completely as your eardrum vibrates to then transmit the sound to your brain.
It happens 440 times per second. If I were to change the amplitude of these peaks, it would sound louder. I'll raise the peaks by raising the decibel level, or the amplitude of the volume, depending on the term that you'd like to use. Now you can see now they are much higher, which means now the peak is higher, the valley is lower, and so this will be a louder tone. (Tone playing.) Simple enough to raise the tone. You can see that that's reflected in the soundwave by the height of the soundwave. I'll do Ctrl+Z to undo that. Let me show you how octaves look.
I am going to open up the entire file so you can see that there's several tones here. (Tone's playing.) Each one of those tones is an octave higher, and the cool thing about sound is that we hear the octave. It's something sort of inherent in us to be able to hear dum... dum... dum... to hear that octave, doh ... doh... and in fact, the octave is double the frequency. So, let me show you something called the Spectral Frequency Display. If you click this button, that opens it up, or you can just drag it up this way, and this shows those tones.
The first tone, (Tones playing.) 440 cycles per second. You can see it right there 400. A little bit above there is 440. Now if I double that, it will be 880. (Tones playing.) If you look over here, you see it's about 880 there. If I double that, it will be 1760. (Tones playing.) That's about 1760 there. (Tones playing.) Then 3520, and then 7040. Now about this time, my dog starts running out of the house. These high-frequency tones are just tough on dogs. They just get all anxious if they start hearing this. Your dog might be doing the same thing right now.
(Tone playing.) And that's the highest one you probably - if your hearing is acute, your hearing is 14,000 or so cycle tone. And other people can't hear it. You notice that if you look up here, you'll see that it's being displayed in terms of the decibel level, but if your hearing is not really great, you might not hear that. Human hearing ranges from about, we'll say 20 or so cycles per second, which is a real low note. Let me go over there (Tone playing.) or it can go up to about 20,000 or so.
And if you can't hear that tone, there at 14,000, that would be not unusual for people. As they get older, they start losing their hearing at that particular level. So, this is basically how audio works. You can see the various frequencies here. As you double the frequency, you increase the pitch by an octave and as you cut the frequency in half you decrease the pitch by an octave, and then the pitch is determined by the cycles per second and the decibel level is dependent on the heighth of the waveforms.
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