Sound
Acoustic energy travelling as a mechanical wave through a medium (often air).Sound travels through air and depends on air pressure (density of air molecules). The speed at which sound waves propagate depends on the density of the medium in which it's travelling. See specific values [see page 3, here].
Sound waves are measured in pascals or relative to another wave using Decibels.
Like all waves sound waves have Frequency and Wavelength. We can relate these two fields using the formula for velocity \(v = \lambda * f\).
The speed of sound is: \(343 m{s^-1}\)
Variations
The different types of sound reflect the different ways in which sound pressure can differ over time:
| Kind | Examples |
|---|---|
| Impulsive | Explosion. Handclap |
| Noisy | Wind. Surf on the beach |
| Repetitive | Buzzing Insect, Tuning Fork |
Sound Speaking by the human vocal system has it's own [see page 16, categories].
| Type | Description | Example |
|---|---|---|
| Voiced | Vocal cords are vibrating | "Aaaaaa", "Zzzzzzzz" |
| Unvoiced | Vocal cords are not vibrating | "Shhhhh", "ssssssss" |
| Fricative | Sound from turbulent airflow at a constriction | "fah" |
| Plosive | Sound occuring after a blockage is released | "puh!" |
Note: voiced and voiceless plosives really only [see page 14, differ] in the timing of the Voice Onset Time. Voiced VOT is often much lower than voiceless VOT.