- Learn the differences between amplitude & frequency.
- Discover how they are used in music.
- Get to grips with FM vs AM
Frequency and amplitude are the building blocks of music, and whether we know it or not, we use them every day.
When a singer performs a crescendo and begins to sing louder, their voice increases in amplitude. Similarly, when the singer sings a higher note, their voice increases in frequency.
While the concepts of frequency and amplitude span across all spheres of music, they have been developed and taken to great lengths within the field of synthesis and audio in general.
Let’s take a look at some definitions, contextual history, and audio applications!
Amplitude & Frequency
Differences
- Amplitude is the loudness of the sound. It is measured in decibels (dB) and is determined by the height of a sound wave when displayed on a graph.
- Frequency is the pitch of the sound. It is measured in Hertz (Hz) and is determined by how many cycles per second a wave vibrates. The faster the sound vibrates, the higher the frequency or pitch of the sound.
Simply put, amplitude measures the wave’s “size,” while frequency measures how quickly the wave oscillates.
Historical Context
AM synthesis can be traced back to early radio technology when amplitude modulation was used for audio transmission. Edwin Armstrong’s pioneering work in radio recognized AM’s creative potential.
FM synthesis can be traced back to John Chowning’s analog synth explorations at Stanford University in the 1960s. Chowning’s research into frequency modulation resulted in the creation of the first FM synthesis algorithm, which revolutionized electronic music.
Fun Fact: Chowning’s work directly influenced the development of the first commercial FM synthesizer, the Yamaha DX7, which became one of the most popular and influential synthesizers of the 1980s.
Understanding The Physics
Sound is simply a vibration of air pressure. A sound source, like a guitar string or synthesizer, vibrates and sends vibrations through the air.
When we graph a sound wave, we see the wave’s energy fluctuating over time.
Amplitude is simply the amount of energy of the wave at its peak. It refers to the loudness of the sound. The higher the amplitude, the louder the sound wave.
To measure amplitude, we look at the distance from the center of a wave to its peak or trough. Amplitude is measured in decibels (dB).
Frequency is the number of cycles the wave goes through per second. This is measured in Hertz (Hz), where 1 Hz equals 1 cycle per second.
The higher the frequency, the higher the pitch of the sound.
In the image below, you can see the note middle C and each octave of the note A, namely A3, A4, and A5, along with their frequencies.
As you go up the keyboard, the frequencies rise and sound higher in pitch.
Wrapping Up
Hopefully, you now understand the differences between Amplitude and Frequency, how they are used in synthesis, and their influence on music culture throughout history. These fundamental building blocks of sound have shaped how we make music today.
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