PHYSICS OF SOUND

SOUND• An oscillation through matter• A transfer of energy• Takes the form of a mechanical

wave of pressure and displacement

• Moves outward from the point of origin

• Sounds can interact with other sound and objects (reflectivity, interference, refraction)

WHAT IS A WAVE?Waves move over long distances – the movement of the material it passes through is limited.What we ‘see’ when we see a wave is the energy moving through matter.To create a wave, there needs to be some initial energy input.

TYPES OF WAVES• Longitudinal wave

• along direction of motion

• Transverse wave• at right-angle to

direction of motion• Surface wave

SOUNDWAVES

MECHANICAL WAVES• Also known as pressure or compression waves• Energy propagates in the same direction as

the wave

𝐴 (𝑥 ,𝑡 )=𝐴0 cos (𝑘𝑥−𝜔𝑡+𝜙)

𝐸∝ 𝐴2 𝑘=2𝜋𝜆 𝜔=2𝜋 𝑓

𝑣= 𝑓 𝜆=𝜆𝑇 =

𝑑𝑖𝑠𝑡𝑎𝑛𝑐𝑒𝑡𝑖𝑚𝑒

CHARACTERISTICS OF WAVESAmplitude – how tall the wave is from its point of equilibrium to its peak.

Angular frequency – the time it takes to go through a whole wave cycle, trough to trough or peak to peak.

Sound pressure / Intensity – sound power per unit area.

Wave number – The higher this number is, the higher this pitch will be.

CHARACTERISTICS OF SOUND• Pitch – how “high” or “low”• Duration – how “long” or “short”• Loudness – how “loud” or “soft”• Timbre – the perceived quality of the sound. A guitar as opposed to a

piano or thud of a falling rock or a mechanical drill.• Sonic Texture – the number of sound sources and the interaction between

them. A quartet as opposed to an orchestra.• Spatial Location – the distance and location of the sound source.

INTERFERENCE PATTERNS• When waves overlap, they add and subtract.

STANDING WAVES• A phenomena that is caused by waves being reflected back and forth

inside of a medium at specific frequencies or two waves traveling in opposite directions.

STANDING WAVES

SUMMARY• Waves are cyclical.• Waves can be described by a few simple values, mostly: , , , and .• Waves move away from the point of origin radially and lose power by • Waves can add together or subtract from each other, based off their

amplitude.• Standing waves form from interference

ContactBlake Nicholson