ABSTRACT
Forced particle motion forms wave patterns and so allows sound to carry through the air. This wave motion allows noise to diffract, propagate and curve like any other wave motion which is why sound can be heard round corners or through small gaps in a structure. Acoustic absorption occurs when sound comes into contact with an acoustically porous material. In a bedroom the carpet, curtains, bed and bedding are all acoustically absorbent and so have the effect of reducing the reverberation time (echo) within a space. The more distant a noise building is from a noise source then quieter the level of noise from the source will be within the building. This will depend upon wither the noise source is considered as a point source, such as individual items of fixed plant or as a line source, such as noise from a railway line or motorway.
