PhysicsChapter 4: Sound
Nature of Sound Waves
Introduction
Sound waves in air are longitudinal mechanical waves.
Definition
Longitudinal
Air particles vibrate approximately parallel to the direction in which the sound wave travels.
Mechanical
Sound needs a material medium.
Pressure and Density Variation
Sound consists of alternating compressions and rarefactions. Compression: higher local pressure and density. Rarefaction: lower local pressure and density.
Frequency
Frequency determines pitch.
Amplitude
Amplitude is related to sound intensity and perceived loudness.
Speed
Sound speed depends on properties of the medium and temperature.
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SOUND IN AIR
- Longitudinal
MECHANICAL
- Needs medium
COMPRESSION
- High pressure
RAREFACTION
- Low pressure