Classification of Sound

In physics, sound is a vibration that propagates as a typically audible mechanical wave of pressure and displacement, through a medium such as air or water. In physiology andpsychology, sound is the reception of such waves and their perception by the brain

Sound is a longitudinal, mechanical wave.

Sound can travel through any medium, but it cannot travel through a vacuum. There is no sound in outer space.

Sound is a variation in pressure. A region of increased pressure on a sound wave is called acompression (or condensation). A region of decreased pressure on a sound wave is called ararefaction (or dilation).

The sources of sound

  • vibrating solids
  • rapid expansion or compression (explosions and implositons)
  • Smooth (laminar) air flow around blunt obstacles may result in the formation of vorticies (the plural of vortex) that snap off or shed with a characteristic frequency. This process is called vortex shedding and is another means by which sound waves are formed. This is how a whistle or flute produces sound. Aslo the aeolian harp effect of singing power lines and fluttering venetian blinds.

What are the different characteristics of a wave? What are the things that can be measured about waves? Amplitude, frequency (and period), wavelength, speed, and maybe phase. Deal with each one in that order.

Amplitude, Intensity, Loudness, Volume

Amplitude goes with intensity, loudness, or volume. That’s the basic idea. The details go in a separate section.

speed of sound

The speed of sound depends upon the type of medium and its state. It is generally affected by two things: elasticity and inertia.


v = √ K  = √ γP  = √ γkT
ρ ρ M
K = bulk modulus
ρ = density
γ = cP/cV (specific heat ratio)
P = absolute pressure
k = boltzmann’s constant
T = absolute temperature
M = molecular mass


v = √ E
E = young’s modulus
ρ = density


v = √ K
K = bulk modulus
ρ = density

Video materials for Classification of Sound: