1. SURFACE EFFECTS AND PROPAGATION CHARACTERISTICS
Sound propagating through air encounters objects that will redirect it, absorb it, bend it, and or scatter it
Depending on the environment some or all of these can take place

2. Reflection
The sound signal hits a flat hard surface and reflects an identical wave from the surface at the same identical angle that it approached it at (angle of incidence)
In such conditions sound
reflects away from the surface
and loses intensity inversely
as distance increases
NB The above conditions do not
Usually take place rather we
have diffusion due to curved and
deformed
surfaces.

3. Diffusion
Is the same as reflection but sound waves impact irregular surfaces. Thus the scattering happens at many different angles
If the irregularities are 0,25 wavelength the effect is perceptible

4. Diffraction
Sound waves bend around the surface of an object. This happens when an object is greater than the wavelength of an approaching sound wave.
The creation of an acoustic shadow takes precedence hence a strong attenuation of the sound behind the object

5. Absorption
A sound signal impacts a surface and some of the signal gets absorbed.
In highly absorptive material the energy behind the sound wave gets dissipated and preventing reflection from taking place.

6. Refraction
Sound waves passing through one medium to another refract ie the direction of the sound changes due to the change of speed of sound in one medium to the other.
The angle of incidence of the incoming sound wave differs with the angle of refraction after it enters the other medium
Sound passing from a thinner/less dense to a thicker/denser material refracts away from the surface of the denser medium.

7. Sound pressure levels (SPL)