The Basics of Sound Waves: A Sound Engineer’s Perspective

As sound engineers, we build our work on sound waves. Be it recording vocals, mixing tracks, designing an immersive soundscape, or perfecting a live performance, knowing the science behind sound waves is the foundation to delivering great audio.

In this week's #SoundSaturdays, let's dive into the basics of sound waves, their properties, and how they affect our work as sound engineers.

What Are Sound Waves?

At their heart, sound waves are vibrations through a medium: air, water, or solids that our ears interpret as sound. These vibrations create pressure changes in the medium, moving in patterns we call waves.

For sound engineers, these waves are not just physical phenomena-they are the raw material we shape into art.

Key Properties of Sound Waves

Here are the main properties of sound waves that every sound engineer should know:

1. Frequency

Definition: The number of wave cycles per second, measured in Hertz (Hz).

Perception: Frequency determines the pitch of a sound. Higher frequencies correspond to higher pitches, while lower frequencies produce deeper tones.

Application: Audio equalization will increase frequencies for better clarity and balance. Example: increasing the high frequencies increases the brightness in vocals; lowering the low frequency can minimize the rumble.

2. Amplitude

Definition: The vertical height of the wave; amplitude is a measurement of energy or strength of sound.

Perception: The size of amplitude reflects loudness. A bigger amplitude is louder and a smaller amplitude is quieter.

Application: Controlling amplitude is essential for dynamic range. Compressors and limiters reduce peak levels to keep mixes or live performances at similar loudness levels.

3. Wavelength

Definition: The physical space between two successive wave crests.

Relationship to Frequency: The higher the frequency, the shorter the wavelength. Conversely, the lower a frequency, the more wavelength it has.

Application: In live sound, wavelength helps with speaker placement and phase cancellation.

4. Phase

Definition: The relative timing of waves. When two sound waves are aligned, they are "in phase," and their amplitudes combine. When they don't align, they are "out of phase," and may cancel each other out.

Application: Phase problems occur when using more than one microphone. Techniques such as proper mic placement and polarity inversion can help resolve these problems.

5. Timbre

Definition: The characteristic or color of a sound, determined by its harmonic content.

Perception: Timbre is what makes a guitar sound different from a piano, even if they play the same note at the same volume.

Application: As sound engineers, we shape timbre using EQ, filters, and effects to give each instrument or voice its distinct identity.

How Sound Waves Impact Everyday Audio Work

Understanding sound waves is not just theoretical—it directly impacts our day-to-day work:

Recording: Selection and placement of microphones rely on a comprehension of the properties of how sound waves react with the space and the hardware.

Mixing: Balancing frequencies, dynamic control, and phase problems depend on the physical properties of the sound wave.

Live Sound: Managing reflections, delays, and interference is ensuring that audiences have clear and strong sound.

Sound Design: Producing realistic or otherworldly audio often entails manipulation of the sound wave using synthesis and effects.

Practical Tips for Engineers

Use Your Ears and Eyes: Tools like spectrum analyzers are great, but your ears are the ultimate judge. Train them to recognise frequency ranges and phase issues.

Experiment with Phase: Sometimes slight adjustments to mic placement or polarity can fix phase cancellations that compromise your mix.

Leverage Acoustics: Learn how sound waves behave in different environments. Understanding room modes and reflections will improve your mixes and recordings.

Stay Curious: Sound waves are complex, and there's always more to learn. Dive into acoustics, psychoacoustics, and signal processing to refine your skills.

Conclusion

As sound engineers, we are the sculptors of sound waves. By mastering their properties, we gain the power to craft audio that resonates with clarity, emotion, and impact.

Let's keep discovering and sharing the wonders of sound together! Please share your thoughts or questions in the comments below, and tune in next week for #SoundSaturdays!.