tags: mus-407 sound-waves sound
Sound Waves
What is sound?
- Vibration occurring in physical medium
- Vibration causes particle displacement (disturbs particles)
- Particle displacement causes pressure variations
- Propagates away from source in all directions
pressure variations = sound wave
A sound wave transports energy/information, not particles themselves.
The particles themselves do not move from point A to B (although they do move) - it's the wave through particles that move.
While we think of longitudinal waves in 1 direction, it is important to remember that these sound waves move omnidirectionally
- Ex: If I clap my hand, the waves will go out in a sphere
Wave Types
[Transverse] vs. [Longitudinal]
Sound waves are longitudinal in the air, but often depicted as transverse
Wave Features
Compression: region of pressure higher than equilibrium (squished together)
Rarefaction: region of pressure lower than equilibrium (spread apart)
Waveforms
[[Waveform]]: graphical depiction of pressure changes at a point in space over time
- depicts pressure / time
- regular pattern of pressure variations, exhibiting a loss of energy over time
Wave Phenomena
By nature, sound waves can experience the following phenomena:
Reflection & Absorption
Sound waves can be reflected and absorbed by objects and surfaces (usually a combination of both).
Reflection patterns very complex in enclosed spaces.
Materials often strategically chosen to optimize a room's acoustic properties - acousticians are trained to choose and implement these materials to acoustically treat rooms.
Sympathetic Vibration and Resonance
Sympathetic vibration occurs when a sound wave encounters an object and causes it to vibrate in a similar manner
- e.g. acoustic guitar string vibrations transfer to bridge, body, and air-filled cavity
Objects have natural modes of vibration based on shape, material, density, elasticity
When stimulated at one of its natural modes, an object exhibits increased vibrational energy/displacement, called [resonance]