The Physics of Sound
Sound is all around us. It’s in the buzz of traffic, the rhythm of music, the chirping of birds, the hum of the refrigerator, and the tone of my children's voices. At its core, sound is energy moving through stuff—air, water, metal, and the body. The concept of ‘energy moving through stuff’ is indeed ancient: in my studies of Daoist cosmology, this is the way that Qi gets described.
I have learned that sound has a whole world of physics working behind the scenes. From the first tiny vibration to the complex ways our brains process pitch and tone, sound is a mix of movement, energy, and perception. And when you really understand how it all works, you can start using it intentionally—whether that’s for making music, designing immersive sound experiences, or helping people feel more calm and connected.
In these writings, I would like to outline the basics, both to inculcate my learning and to offer this information back out via my website. Vibration, frequency, pitch, loudness, and resonance are the building blocks behind everything from a symphony to a sounding with singing bowls.
Vibration: Where Sound Begins
Sound starts with something shaking. Literally. When an object vibrates, it pushes and pulls on the particles around it. Those little pushes travel through the air (or another medium), kind of like a ripple in water. When those ripples reach your ears, your brain interprets them as sound.
Example: I really enjoyed the videos in our class materials depicting how sound moves through, salt, sand, and water. I went deep into researching the Chladni Plate. The Chladni plate is a metal plate that’s sprinkled with fine sand, salt, or even powder. When the plate is vibrated—usually with a violin bow or a speaker emitting a pure tone—it starts to resonate at specific frequencies. These vibrations move through the metal plate, creating standing wave patterns. The sand or salt moves away from the vibrating parts of the plate and settles into the areas that aren't vibrating—called nodes. The result? Beautiful, symmetrical patterns that visually map the frequency of the vibration. These patterns change depending on the pitch being played.
The higher the frequency, the more complex and intricate the patterns become. It has many practical applications:
in sound healing & education, to help people understand how vibration affects matter.
in cymatics (the study of visible sound): Artists and researchers use it to explore the relationship between sound and form.
as a performance piece: Some musicians and artists incorporate Chladni patterns into live shows for an added layer of visual resonance. My co-founder and I plan to do a residency at RPI this fall and will experiment with using one.
Sound partials are the breakdown of tones into its parts. All sound partials have individual properties such as pitch and volume. The fundamental tone is the lowest, most dominant tone. Other partial tones are overtones. When the ratio of the frequency of the fundamental to the overtone is equal to a positive integer multiple, it’s called a harmonic. Harmonics are an integral part of sound: they are integer multiples of a fundamental frequency. If the fundamental is 100 Hz, the first harmonic is 200 Hz, the second harmonic is 300 Hz, and so on. The harmonic series has a mathematical relationship to the fundamental frequency. With overtones, there is not an exact mathematical integer relationship with the fundamental. Natural sounds from voices, nature, or instruments are rich in overtones.
Frequency: The Speed of Vibration
Frequency is all about how fast something is vibrating. It's measured in hertz (Hz)—meaning cycles per second. High frequency = fast vibrations, like a whistle. Low frequency = slow vibrations, like a djembe beat. Frequency is a big deal because it’s directly tied to what we perceive as pitch.
Examples:
Musical notes: the A above middle C vibrates at 440 Hz. Double that to 880 Hz and you get the same note an octave higher.
Binaural tones, also known as “binaural beats”: these happen when you play two slightly different frequencies in each ear—your brain picks up the difference between them. For example, 210 Hz in one ear and 200 Hz in the other creates a perceived 10 Hz frequency, which can help sync your brainwaves.
Our work with the Third Tone Project creates immersive audio experiences that use specific frequencies to help guide listeners into meditative or focused mental states—tapping into alpha, theta, and other brainwave ranges.
Pitch: What Frequency Sounds Like
Pitch is how high or low a sound seems to us—and it’s basically how we perceive frequency. While frequency is a number, pitch is what your brain makes of it. Different people might hear the same sound slightly differently depending on age, hearing ability, and even cultural background.
Examples:
Voices: A child’s voice usually has a higher pitch because their vocal cords are shorter and tighter. A bass singer’s deep voice is caused by slower-vibrating vocal cords.
Polyphonic singing / Overtone singing: Using the human voice as a sound healing instrument is ancient and powerful. Vocal toning involves holding a specific pitch—like a low hum or vowel sound—and allowing its vibration to resonate in the body. In a group setting, a facilitator may guide participants to tone the vowel "A" at a middle pitch (around 440 Hz) to open the heart space. The collective resonance can help create a deeply present atmosphere.
Amplitude: How Big the Vibration Is
Loudness, or amplitude, has to do with how strong the vibration is—technically, the amplitude of the sound wave. Bigger amplitude = louder sound. Loudness is measured in decibels (dB), and our ears are pretty sensitive to changes.
Examples:
Whisper: Around 30 dB.
Normal conversation: About 60 dB.
Rock concert: Often 100 dB or more (bring earplugs!).
Resonance: When Everything Lines Up
Resonance happens when an object or system naturally vibrates at a certain frequency—and then something else comes along and vibrates at that same frequency. The two amplify each other, and suddenly, the sound gets a lot stronger without much extra effort.
Examples:
Wine glass trick: Hit the right note and the glass vibrates so much it might even shatter.
Bridge collapse, like the one at Tacoma Narrows in 1940: Wind happened to hit the bridge’s natural frequency, causing it to wobble out of control and eventually collapse. Resonance can be beautiful—or dangerous.
Applications:
Musical instruments: The wooden body of a guitar or violin is shaped to resonate with the strings, making the sound louder and richer.
In sound healing, resonance is everything. Whether it’s using tones that resonate with specific frequencies in the body or tuning sound spaces to naturally amplify certain vibrations, sound practitioners can lean into resonance to support their listeners' experiences.
Consonance and dissonance shape our emotional reaction to sound, while resonance taps into our physical and energetic response.
Understanding the difference—and how to use each intentionally—is at the heart of everything from music composition to sound therapy. Whether crafting a song, leading a sound bath, or just tuning into the environment, these principles help create sound that moves people—inside and out.
