Learn how sound is created and what sound waves are, including a lesson on compression and rarefaction.
- [Narrator] To understand how Pro Tools processes audio, it helps to first get an understanding of what sound is, how it travels, and what some of its characteristics are. Here, we'll explore how sound is created. We'll learn about compressions and rarefaction to understand how sound waves behave, and we'll also cover the impact of amplitude and frequency on the audio events we hear. When a physical event occurs in nature it causes vibrations that we perceive as sound. A pluck on a guitar string, or the slam of a bedroom door.
The vibration of the object causes changes in the surrounding air pressure. As air molecules are displaced, the pressure changes, creating regions of high pressure in some areas, and low pressure in others. This is known as compression and rarefaction. As the vibration continues, a repeating pattern of compressions and rarefactions occurs, creating a sound wave. The sound wave moves through the acoustic space, eventually reaching our ears where we perceive it as a sound. If we measure the changes in air pressure using a microphone or other transducer, the amount of air displacement can be seen as the amplitude of the measurement.
This affects our perception of the loudness of the sound. We measure amplitude, or loudness, in decibels, or DB. By measuring how many times the cyclical pattern of compressions and rarefactions occurs per second, we can determine the frequency of the sound wave. The frequency affects our perception of the pitch of the sound. We measure frequency, or pitch, in cycles per second, or hertz. The graphical representation created by measuring the sound wave is what we commonly refer to as a waveform.
The waveform is the shape of the sound, including how the sound changes over time, often referred to as the sound's envelope. The waveform of the sound is what gives the sound its character and makes it unique. It's how we can tell the pluck of a guitar string (plucked guitar string) from the strike of a snare drum. (snare drum tap) When we record sounds into Pro Tools, we must accurately capture the characteristics of amplitude, frequency and waveform of the sound wave. Failure to correctly represent any of these characteristics will result in distortion of the recorded sound.
For information on how an audio waveform is converted to an electrical signal, be sure to check out the video on transducers and for information on how an audio waveform is converted to a digital signal for computer processing, check out the video on analog to digital converters later in this chapter.
AuthorFrank D. Cook
- Getting started with Pro Tools menus, windows, and edit tools
- Creating a session
- Creating a click track
- Recording audio
- Importing audio and video
- Recording, viewing, and editing MIDI data
- Selecting and navigating within tracks
- Adding markers
- Editing clips
- Creating fade effects
- Mixing tracks and adding automation
- Backing up a session
- Bouncing a mix to disk
Skill Level Beginner
Q. This course was updated on 03/23/2017. What changed?
A. Challenges and solutions were added to chapters 3–10 and three videos were updated in the first couple chapters.
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Get In the Mix with Pro Toolswith Brian Lee White2h 46m Intermediate
Mixing Techniques for Pop Music Part 1with Brian Malouf3h 19m Intermediate
1. Getting to Know Pro Tools
2. Getting inside Pro Tools
3. Creating Your First Session
4. Making Your First Audio Recording
5. Importing and Working with Media in a Session
6. Making Your First MIDI Recording
7. Selecting and Navigating
8. Basic Editing Techniques
9. Basic Mixing Techniques
10. Finishing Your Work
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