About this Video

• Video Title: Audio Basics, Episode 1: Signals, Waves, Mixing, and the Physics of Audio
• Channel: Doug Johnson Productions
• Speakers: Doug Johnson
• Duration: 00:46:22

Introduction

This video is the first in a series on audio production fundamentals. Doug Johnson, with over 30 years of experience in audio production, explains sound waves, their propagation, electrical conversion, and how they combine, focusing on the physics involved in creating good-sounding audio.

Key Takeaways

1. Sound Waves and Pressure: Sound is represented by waves; upward movement signifies increased air pressure (compression), while downward movement indicates decreased pressure (rarefaction). The frequency of pressure changes equals the sound's frequency.
2. Sine Waves: The purest sound is a sine wave, visually represented as a smooth, repeating curve. Frequency doubling or halving creates an octave change in musical terms.
3. Wave Combination: Multiple sound sources combine; their waves are added, resulting in a composite wave. Inverse waves cancel each other out, a principle used in noise-canceling headphones.
4. Balanced vs. Unbalanced Audio: Balanced audio (XLR, TRS) uses two signals (one inverted), improving noise reduction by canceling out noise picked up along the cable. Unbalanced audio (RCA, TS) carries only one signal, making it more susceptible to noise.
5. Phase and Delay: The phase of a wave affects its combination with others; 180° out-of-phase waves cancel, while delays between signals create unwanted artifacts.

[{"start_ms":"560","end_ms":"7000","text":"hey everybody Doug here I have promised for a long time that I was going to do a series on audio in terms of doing","start_time_text":"0:00"},{"start_ms":"7000","end_ms":"13480","text":"production my channel viewers are normally involved in video production but this series is going to be appropriate for anybody who wants torn","start_time_text":"0:07"},{"start_ms":"13480","end_ms":"20640","text":"audio as well though I may emphasize some of the video aspects of it just a little bit more so anyway um as","start_time_text":"0:13"},{"start_ms":"20640","end_ms":"27279","text":"mentioned my name is Doug I've been doing audio production for more than 30 years started in the late 80s been doing","start_time_text":"0:20"},{"start_ms":"27279","end_ms":"33680","text":"it kind of uh on the side for pretty much entire time since then and I focused more on video for the last 25","start_time_text":"0:27"},{"start_ms":"33680","end_ms":"39879","text":"years or so but audio has always been at it's always been dear near and dear to my heart and I'm kind of known in this","start_time_text":"0:33"},{"start_ms":"39879","end_ms":"45160","text":"area as the audio snob in terms of people who are doing video but anyway so","start_time_text":"0:39"},{"start_ms":"45160","end_ms":"51520","text":"this lesson is going to be the first of many I don't know exactly how many I haven't planned that out just yet but","start_time_text":"0:45"},{"start_ms":"51520","end_ms":"57039","text":"this one's going to be there to sort of weigh the groundwork let lay the foundation for additional stuff that","start_time_text":"0:51"},{"start_ms":"57039","end_ms":"63120","text":"we're going to cover later on so as such this one's going to be focusing more on some of the fundamental principles like","start_time_text":"0:57"},{"start_ms":"63120","end_ms":"70960","text":"what is a sound wave how does it propagate what does it look like when it's converted to electricity and how","start_time_text":"1:03"},{"start_ms":"70960","end_ms":"77320","text":"those things all sort of interplay with one another and one of the big focuses of this video is going to be how","start_time_text":"1:10"},{"start_ms":"77320","end_ms":"83280","text":"different audio signals combine because that's going to be really important when we start to talk about how to produce","start_time_text":"1:17"},{"start_ms":"83280","end_ms":"89479","text":"good sounding audio because it's kind of kind of important to know what's going on physics wise in what's happening","start_time_text":"1:23"},{"start_ms":"89479","end_ms":"94880","text":"inside the mixer and in the air as well so anyway this is going to be a bit of a","start_time_text":"1:29"},{"start_ms":"94880","end_ms":"101720","text":"lengthy video so grab a snack grab a drink sit down in a comfortable chair and enjoy the ride so here we go so I'm","start_time_text":"1:34"},{"start_ms":"101720","end_ms":"106920","text":"going to guess pretty much everybody has seen this kind of a display before this is the output of an oscilloscope I've","start_time_text":"1:41"},{"start_ms":"106920","end_ms":"113159","text":"got an actual oscilloscope sitting on the desk here and it's showing you the output of the microphone that I'm","start_time_text":"1:46"},{"start_ms":"113159","end_ms":"120640","text":"holding here in my hand and what we're seeing here is the resulting wave that represents the audio that's coming out","start_time_text":"1:53"},{"start_ms":"120640","end_ms":"126439","text":"of my mouth my speech andout the course of this video I'm going to make a little bit more sense of what you're seeing","start_time_text":"2:00"},{"start_ms":"126439","end_ms":"133520","text":"here and what this means and how you can better understand this and understand","start_time_text":"2:06"},{"start_ms":"133520","end_ms":"140560","text":"what's going on with the audio and what that means in terms of the quality of the sound and and we we'll go beyond","start_time_text":"2:13"},{"start_ms":"140560","end_ms":"146480","text":"that as well but just wanted to start with this to kind of let you see what an audio waveform looks like particularly","start_time_text":"2:20"},{"start_ms":"146480","end_ms":"152200","text":"one that's a spoken voice because it look a little bit different than a","start_time_text":"2:26"},{"start_ms":"152200","end_ms":"158000","text":"musical instrument say for example so anyway with that groundwork let's uh start talking about the wave and what","start_time_text":"2:32"},{"start_ms":"158000","end_ms":"164519","text":"that represents this speaker is going to help me to kind of present a little bit uh better what's going on with sound","start_time_text":"2:38"},{"start_ms":"164519","end_ms":"170360","text":"waves uh it provides a nice visual but what's happening with the speaker is essentially what happens with any sort","start_time_text":"2:44"},{"start_ms":"170360","end_ms":"176200","text":"of Sound Source whether it be someone talking a musical instrument explosion whatever you're seeing the same kind of","start_time_text":"2:50"},{"start_ms":"176200","end_ms":"182120","text":"things happening in those cases so the speaker here has a diaphragm It Moves In","start_time_text":"2:56"},{"start_ms":"182120","end_ms":"187400","text":"and Out in response to an electrical signal I don't be able to see that very well on camera but but it moves in and","start_time_text":"3:02"},{"start_ms":"187400","end_ms":"193440","text":"out and as it does so it changes the pressure of the air in front of it so","start_time_text":"3:07"},{"start_ms":"193440","end_ms":"198720","text":"when it presses outward it increases the pressure and then when it retracts","start_time_text":"3:13"},{"start_ms":"198720","end_ms":"204400","text":"backwards it's lowering the air pressure right the air it it provides resistance","start_time_text":"3:18"},{"start_ms":"204400","end_ms":"210239","text":"right it's not it's not something that you can move for free no energy required and so as it's move this speaker cone is","start_time_text":"3:24"},{"start_ms":"210239","end_ms":"217519","text":"moving in out it's increasing and lowering the air pressure in front of that and that wave moves away from the","start_time_text":"3:30"},{"start_ms":"217519","end_ms":"225760","text":"speaker at the speed of sound that makes sense so what we do is we represent that","start_time_text":"3:37"},{"start_ms":"225760","end_ms":"230920","text":"movement or that rather those changes in air pressure in the air with the wave","start_time_text":"3:45"},{"start_ms":"230920","end_ms":"236480","text":"that I showed you a moment ago in the case of the wave that was on screen and the waves that other waves I'm going to","start_time_text":"3:50"},{"start_ms":"236480","end_ms":"242319","text":"show you here in this video an upward movement represents an increase pressure and a downward movement below the center","start_time_text":"3:56"},{"start_ms":"242319","end_ms":"249040","text":"line represents a lowering of the air pressure now that's we call those compression and rare refection portions","start_time_text":"4:02"},{"start_ms":"249040","end_ms":"255040","text":"of the wave and so as I talk about it you'll know what that represents and like this","start_time_text":"4:09"},{"start_ms":"255040","end_ms":"262240","text":"speaker as it always comes back to rest in the center the mo center of the motion tends to be at that resting","start_time_text":"4:15"},{"start_ms":"262240","end_ms":"269320","text":"position likewise in air the natural pressure what we experience at any given","start_time_text":"4:22"},{"start_ms":"269320","end_ms":"275120","text":"point in time time that's sort of the neutral point and then any sound waves are increasing and lowering the pressure","start_time_text":"4:29"},{"start_ms":"275120","end_ms":"280560","text":"from there now these pressure changes uh are changing at the frequency of the","start_time_text":"4:35"},{"start_ms":"280560","end_ms":"286680","text":"sound so if you're listening to a say 400 htz tone the pressure is increasing","start_time_text":"4:40"},{"start_ms":"286680","end_ms":"292280","text":"and then decreasing and then returning back to equilibrium 400 times per second","start_time_text":"4:46"},{"start_ms":"292280","end_ms":"297560","text":"and that tends to look like a sine wave which we will take a look at now so here","start_time_text":"4:52"},{"start_ms":"297560","end_ms":"303400","text":"is a 440 HZ tone this is a sine wave which is the most pure the most simple","start_time_text":"4:57"},{"start_ms":"303400","end_ms":"309320","text":"type of sound that we can produce and hear and I'll let you hear what that sounds like so I'll go ahead and click","start_time_text":"5:03"},{"start_ms":"309320","end_ms":"317000","text":"the play button so there you go that is 440 Hertz or 440 cycles per second and","start_time_text":"5:09"},{"start_ms":"317000","end_ms":"322199","text":"uh for anybody in the music world that's a concert a uh but anyway so what you're","start_time_text":"5:17"},{"start_ms":"322199","end_ms":"327240","text":"seeing here is the A visual representation of what is happening with the with the pressure in the air that is","start_time_text":"5:22"},{"start_ms":"327240","end_ms":"333080","text":"produced as a result of a Sound Source generating sound so a increase above the","start_time_text":"5:27"},{"start_ms":"333080","end_ms":"338800","text":"Baseline here is an increase in pressure and then going below the Baseline here is a decrease in pressure which is the","start_time_text":"5:33"},{"start_ms":"338800","end_ms":"344080","text":"rare faction that I mentioned a moment ago and this whole this one cycle that","start_time_text":"5:38"},{"start_ms":"344080","end_ms":"350000","text":"represents one wave one one half one portion of the wave uh is happening 440","start_time_text":"5:44"},{"start_ms":"350000","end_ms":"356880","text":"times per second okay all right now this is by the way of housekeeping in this software anything you see in white here","start_time_text":"5:50"},{"start_ms":"356880","end_ms":"362639","text":"up top that is the output wave that's being generated by this software and","start_time_text":"5:56"},{"start_ms":"362639","end_ms":"368120","text":"then uh this software has the ability to create multiple waves which I'll get into in a moment but you can see here","start_time_text":"6:02"},{"start_ms":"368120","end_ms":"376080","text":"that my the one wave that I'm generating at this point is the one in red here and that is a 440 htz sine wave okay all","start_time_text":"6:08"},{"start_ms":"376080","end_ms":"381440","text":"right um I'll mention that I created the software just for this video and I'm still kind of undecided as whether I","start_time_text":"6:16"},{"start_ms":"381440","end_ms":"388479","text":"want to make this available for free or not uh but at some point if I do I'll have a link to that in the description","start_time_text":"6:21"},{"start_ms":"388479","end_ms":"394800","text":"down below the video okay anyway so there is a 440 htz tone and you're able to hear what that sounds like now just","start_time_text":"6:28"},{"start_ms":"394800","end_ms":"400520","text":"by the way of reference I'm going to take and I'm going to lower that to half of that frequency 220 HZ you can see","start_time_text":"6:34"},{"start_ms":"400520","end_ms":"405639","text":"that the length of the wave or the wave length has doubled and it sounds like a","start_time_text":"6:40"},{"start_ms":"405639","end_ms":"411120","text":"lower tone but it still sounds like the same note it just one octave lower so","start_time_text":"6:45"},{"start_ms":"411120","end_ms":"418759","text":"anybody who is involved in music familiar with the concept of an octave an octave is a doubling or having of the","start_time_text":"6:51"},{"start_ms":"418759","end_ms":"426440","text":"the frequencies that you're in so there we go and we'll go up to 880 and each time I change uh the octave there it","start_time_text":"6:58"},{"start_ms":"426440","end_ms":"432000","text":"changes the note and the frequency changes by double or half okay all right","start_time_text":"7:06"},{"start_ms":"432000","end_ms":"438960","text":"now the other other thing I wanted to show here before we dive into the software too much is kind of a more three-dimensional well a more visual","start_time_text":"7:12"},{"start_ms":"438960","end_ms":"444039","text":"view of what's going on so imagine this is well we'll say it's an overhead view","start_time_text":"7:18"},{"start_ms":"444039","end_ms":"450160","text":"uh for the sake of discussion here but it really could be any view whatsoever so this in the middle here is is a sound","start_time_text":"7:24"},{"start_ms":"450160","end_ms":"455240","text":"source and it's vibrating at Whatever frequency it's producing the ACT number","start_time_text":"7:30"},{"start_ms":"455240","end_ms":"460879","text":"is not important for what for the sake of discussion here but as it's vibrating you can see that the waves are moving","start_time_text":"7:35"},{"start_ms":"460879","end_ms":"466400","text":"outward from that at in this case the speed of sound anything in white here","start_time_text":"7:40"},{"start_ms":"466400","end_ms":"472240","text":"represents the compression portion of the wave and anything in Black represents the rare ref faction now if I","start_time_text":"7:46"},{"start_ms":"472240","end_ms":"478479","text":"look at this in 3D view this isn't what really happens in 3D but but you'll see that same sine wave that we saw in the","start_time_text":"7:52"},{"start_ms":"478479","end_ms":"484919","text":"other software just a moment ago and as I increase the","start_time_text":"7:58"},{"start_ms":"485159","end_ms":"491599","text":"frequency the spacing between the waves get smaller but they still move out at the same speed and if I decrease the","start_time_text":"8:05"},{"start_ms":"491599","end_ms":"497000","text":"frequency you can see that the spacing between the waves is longer longer","start_time_text":"8:11"},{"start_ms":"497000","end_ms":"502639","text":"wavelength uh and they're coming less frequently lower frequency but the","start_time_text":"8:17"},{"start_ms":"502639","end_ms":"508159","text":"actual speed that they move away from the S the source is always the same okay","start_time_text":"8:22"},{"start_ms":"508159","end_ms":"513518","text":"so these pressure waves that are moving through the air are causing the diaphragm that's in a microphone looks","start_time_text":"8:28"},{"start_ms":"513519","end_ms":"519839","text":"kind of like the diaphragm in the speaker just a lot smaller that cause that diaphragm to move in and out and","start_time_text":"8:33"},{"start_ms":"519839","end_ms":"525120","text":"that generates a voltage which is picked up by a voice coil I'm talking about Dynamic microphones in this case but","start_time_text":"8:39"},{"start_ms":"525120","end_ms":"532320","text":"it's picked up by a voice coil which is then connected to the the output Jack on the back which is the signal that goes through the wires but basically anytime","start_time_text":"8:45"},{"start_ms":"532320","end_ms":"538640","text":"that diaphragm moves inward that's going to generate a positive voltage on the output and anytime that diaphragm moves","start_time_text":"8:52"},{"start_ms":"538640","end_ms":"544800","text":"backwards because of a lower pressure that's going to generate a negative voltage on on the output on the wire and","start_time_text":"8:58"},{"start_ms":"544800","end_ms":"552760","text":"that's what we're seeing on the various graphs and charts that we're going to be looking at here today so that movement back and forth inward positive outward","start_time_text":"9:04"},{"start_ms":"552760","end_ms":"559040","text":"negative and that's happening at the the rate of the frequency that the microphone or combination of frequencies","start_time_text":"9:12"},{"start_ms":"559040","end_ms":"565600","text":"uh are picking up now just a little bit of trivia for you so in the world of audio we talk about analog and we talk","start_time_text":"9:19"},{"start_ms":"565600","end_ms":"571640","text":"about digital and ultimately every every audio source and every playback device","start_time_text":"9:25"},{"start_ms":"571640","end_ms":"577079","text":"pretty much is analog uh but very often we have the signals being conveyed in","start_time_text":"9:31"},{"start_ms":"577079","end_ms":"583160","text":"digital I'll get into the intri intricacies of those in a future video but for right now I wanted to kind of","start_time_text":"9:37"},{"start_ms":"583160","end_ms":"590320","text":"talk about where the word analog comes from and this is something I didn't understand till I had a aord recording studio class in college but what's","start_time_text":"9:43"},{"start_ms":"590320","end_ms":"598800","text":"happening is the the wave that is being conveyed down a wire looks like the sound wave that is","start_time_text":"9:50"},{"start_ms":"598800","end_ms":"605160","text":"being picked up by the microphone in other words it is analogous to that original Source that's where the word","start_time_text":"9:58"},{"start_ms":"605160","end_ms":"611000","text":"analog actually comes from so when we talk about analog audio we're talking about the signals that are traveling","start_time_text":"10:05"},{"start_ms":"611000","end_ms":"616120","text":"through our wies through our mixers the signals that are being picked up by the microphone that being played by the","start_time_text":"10:11"},{"start_ms":"616120","end_ms":"621800","text":"speaker are analogous to the original Sound Source that was being picked up","start_time_text":"10:16"},{"start_ms":"621800","end_ms":"627600","text":"that's where the term comes from so just a little bit of trivia that's kind of cool to know all right with that said uh","start_time_text":"10:21"},{"start_ms":"627600","end_ms":"632839","text":"let's kind of talk about what happens when we have multiple sound sources and","start_time_text":"10:27"},{"start_ms":"632839","end_ms":"639279","text":"how that relates to the the sound pressure level that is occurring as a result of that so I'm going to add a","start_time_text":"10:32"},{"start_ms":"639279","end_ms":"646800","text":"second tone into here and just for the sake of discussion here I'm going to do one at 220 Herz and one at 440 Herz and","start_time_text":"10:39"},{"start_ms":"646800","end_ms":"651880","text":"I'm going to go ahead and play that so you can hear what that sounds like and as you can hear from there","start_time_text":"10:46"},{"start_ms":"651880","end_ms":"659639","text":"there are two distinct tones one Higher One lower and they sound good together because one is a multiple of the other","start_time_text":"10:51"},{"start_ms":"659639","end_ms":"666440","text":"and that creates Harmony and when we're talking about Harmony in audio in music","start_time_text":"10:59"},{"start_ms":"666440","end_ms":"671480","text":"it's it basically means that the relationship between the different frequencies is","start_time_text":"11:06"},{"start_ms":"671480","end_ms":"678880","text":"mathematically uh pleasing I can get I can kind of get into what that means a little bit here more in a bit but if we","start_time_text":"11:11"},{"start_ms":"678880","end_ms":"686880","text":"take a look up here at the top we can see there's the Red Wave that's one 4 140 Herz the Green Wave at 220 HZ and","start_time_text":"11:18"},{"start_ms":"686880","end_ms":"692440","text":"then the white is the combination of the too and what you'll notice here is that","start_time_text":"11:26"},{"start_ms":"692440","end_ms":"699360","text":"there isn't two separate waves being moved that are moving through the air necessarily in this case it's one","start_time_text":"11:32"},{"start_ms":"699360","end_ms":"704440","text":"combined wave and that increase and decrease in air pressure is following","start_time_text":"11:39"},{"start_ms":"704440","end_ms":"710800","text":"this pattern so any given molecule of air that's that's relaying that audio","start_time_text":"11:44"},{"start_ms":"710800","end_ms":"715880","text":"signal that's the sort of movement that it's going to be going to be making as","start_time_text":"11:50"},{"start_ms":"715880","end_ms":"722360","text":"it is propagating that sound wave through the air from source to to","start_time_text":"11:55"},{"start_ms":"722360","end_ms":"728160","text":"listener okay so you don't have a situation where some","start_time_text":"12:02"},{"start_ms":"728160","end_ms":"733399","text":"air molecules are moving at one frequency and other molecules are moving at a different frequency they're all","start_time_text":"12:08"},{"start_ms":"733399","end_ms":"738880","text":"moving kind of the same and the combination of the two frequencies is","start_time_text":"12:13"},{"start_ms":"738880","end_ms":"744680","text":"simplified into a single wave and that's what that wave looks like now mathematically if we wanted to look at","start_time_text":"12:18"},{"start_ms":"744680","end_ms":"750720","text":"it that way what's happening is that the two waves are being summed together they're being added together and that","start_time_text":"12:24"},{"start_ms":"750720","end_ms":"755920","text":"creates a composite wave that uh represents both frequencies together in","start_time_text":"12:30"},{"start_ms":"755920","end_ms":"763279","text":"fact we can can keep adding more and more and more so if I want to do another one here and we'll do this one up","start_time_text":"12:35"},{"start_ms":"763279","end_ms":"769760","text":"at we'll do there 880 HZ you can see that there's now a Blue Wave it's a","start_time_text":"12:43"},{"start_ms":"769760","end_ms":"777360","text":"little bit a little bit hard to see in there but there's a Blue Wave in there now and that has also added to the signal and has made the output wave the","start_time_text":"12:49"},{"start_ms":"777360","end_ms":"782519","text":"way the white one more complicated let you hear that so there you go there's there's","start_time_text":"12:57"},{"start_ms":"782519","end_ms":"789240","text":"three separate tones in there okay now um sine waves are the most fundamental","start_time_text":"13:02"},{"start_ms":"789240","end_ms":"795959","text":"that we uh Sound Source that we deal with but very few sound sources actually are sine waves they're actually lot more","start_time_text":"13:09"},{"start_ms":"795959","end_ms":"802440","text":"complicated than that and at any given time any wave that you are seeing or","start_time_text":"13:15"},{"start_ms":"802440","end_ms":"808800","text":"hearing is different levels different combinations of different frequencies that are being merged together so like","start_time_text":"13:22"},{"start_ms":"808800","end_ms":"815680","text":"the sound to my voice or uh the music coming out of a speaker or a pair of headphones or whatever there's one","start_time_text":"13:28"},{"start_ms":"815680","end_ms":"822399","text":"output wave there but you're hearing all sorts of different frequencies and even within a given instrument or Voice or","start_time_text":"13:35"},{"start_ms":"822399","end_ms":"829240","text":"whatever there are a bunch of uh component frequencies that make that up uh qu quite often that's uh fundamental","start_time_text":"13:42"},{"start_ms":"829240","end_ms":"835519","text":"and some harmonics but there's there can be others as well so what I've done in this software here is I've actually uh","start_time_text":"13:49"},{"start_ms":"835519","end_ms":"841880","text":"added the ability to represent a couple different types of waves that we encounter so so here is a sine wave","start_time_text":"13:55"},{"start_ms":"841880","end_ms":"851360","text":"actually start at 220 it's a little easier to hear there we go so 220 and as I drag from a sign over to a square","start_time_text":"14:01"},{"start_ms":"851360","end_ms":"856959","text":"wave you see that that Wave It's got some sharp edges on it and those sharp","start_time_text":"14:11"},{"start_ms":"856959","end_ms":"864399","text":"edges show up as high frequencies and so it's got this is edgier it's more aggressive then we go over here to a