Teach Me Audio

Waveforms

A waveform visually represents a sound wave's journey through a medium over time. Learn how waveforms illustrate sound characteristics.

Any waveform has four fundamental characteristics: frequency, wavelength, amplitude, and velocity.

Don't confuse a waveform with the true nature of sound. Sound waves are longitudinal, where particle vibrations occur in the same direction as the wave travels. However, waveforms are often shown as transverse in audio diagrams for easier visualization.

Frequency

Frequency is how many complete waves pass a certain point per second. It indicates the rate of pressure variations or cycles per second of a wave, measured in Hertz (Hz).

The frequency of a sound determines its pitch - the subjective sensation of how low or high a sound is perceived.

  • Lower frequency sound waves have longer wavelengths and a lower pitch.
  • Higher frequency sound waves have shorter wavelengths and a higher pitch.
Frequency chart comparing lower and higher frequency soundwaves
Figure 1 - Frequency chart comparing lower and higher frequency sound waves

Sine wave at 100 Hz:
Sine wave at 1000 Hz:

The frequency range in which humans can hear is 20 Hz to 20,000 Hz, which is known as the audible range or audio spectrum.

Wavelength

Waveform diagram showing the wavelength of a soundwave
Figure 2 - Waveform diagram showing the wavelength of a sine wave

Wavelength is the distance between two successive points on a wave that are in phase (e.g., from crest to crest or trough to trough). Wavelength is inversely related to frequency.

Amplitude

Waveform diagram showing the amplitude of a soundwave
Figure 3 - Waveform diagram showing the amplitude of a sound wave

Amplitude is the height of the wave, which determines the perceived loudness of the sound. A higher amplitude means a louder sound.

Amplitude is measured in two primary ways:

  1. Zero to peak: Measures the maximum positive or negative signal level.
  2. Root-mean-square (RMS): Measures a more meaningful average level, closer to how humans perceive loudness over time.

Velocity

Velocity is the speed and direction of a sound wave. Sound waves travel at different speeds through different mediums. Through the air at room temperature, sound travels at approximately 344 meters per second.

Generally speaking, the denser the medium, the faster sound travels through it.

Understanding these four fundamental waveform characteristics is essential for tackling equalization, compression, and spatial audio manipulation in your mixes.

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