The Physics of Music

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Sound Noun

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[sound]

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Sound

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A form of energy produced by a vibrating object that travels as pressure oscillations through a medium like air.

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Example: Sound travels as a longitudinal wave, creating areas of high pressure (compressions) and low pressure (rarefactions), which can be graphed to show its properties.

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Oscillation Noun

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[os-uh-ley-shuhn]

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Oscillation

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A regular variation in magnitude or position around a central point, such as the pressure changes in a sound wave.

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Example: This diagram shows an oscillation as a wave moving up and down around a central line, like a vibrating guitar string creating a sound wave.

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Reed Noun

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[reed]

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Reed

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A thin strip of material that vibrates when air is blown across it, producing sound in certain musical instruments.

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Example: This image shows a reed instrument and several spare reeds. The reed is the small, thin piece at the mouthpiece that vibrates to create sound.

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Sounding board Noun

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[sound-ing bohrd]

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Sounding board

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A surface on a stringed instrument that vibrates with the strings to amplify the sound by moving more air.

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Example: This diagram identifies the sounding board on an acoustic guitar. This large wooden top surface vibrates when the strings are plucked, amplifying the sound.

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Vocal cords Noun

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[voh-kuhl kordz]

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Vocal cords

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Two membranes in the throat that vibrate as air passes through them, producing the sound of the human voice.

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Example: This diagram shows the vocal cords inside the larynx (voice box) and how they open to let air pass and close to vibrate, producing sound.

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Pitch Noun

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[pich]

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Pitch

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The perceived highness or lowness of a sound, which is determined by the frequency of its vibrations.

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Example: This diagram shows that low-pitched sounds are made of waves with a long wavelength, while high-pitched sounds are made of waves with a short wavelength.

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Resonance Noun

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[rez-uh-nuhns]

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Resonance

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The phenomenon of increasing a vibration's amplitude by applying a periodic force at the system's natural frequency.

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Example: A vibrating tuning fork held over a tube causes the air inside to vibrate. When the air column is the right length, it resonates, amplifying the sound.

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Natural frequency Noun

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[nach-er-uhl free-kwuhn-see]

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Natural frequency

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The specific frequency at which a system oscillates when not subjected to a continuous or repeated external force.

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Example: A vibrating object, like a guitar string, has specific patterns of vibration called modes, each with its own natural frequency. Higher modes have higher frequencies.

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Closed-pipe resonator Noun

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[klohzd-pahyp rez-uh-ney-ter]

Back

Closed-pipe resonator

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A resonating tube with one end closed, which amplifies sound waves when its length is an odd quarter-wavelength multiple.

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Example: This diagram shows how a closed-pipe resonator works. A tuning fork creates sound waves that travel down a tube, reflect off the water (the closed end), and create a loud, resonating sound at specific air column lengths.

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Standing wave Noun

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[stan-ding weyv]

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Standing wave

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A wave pattern with stationary nodes and antinodes, created by the interference of two waves traveling in opposite directions.

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Example: This diagram shows how a string, like on a guitar, creates standing waves. It displays different wave patterns (harmonics) and labels the still points (nodes) and high-vibration points (antinodes).