Sound and vibrations in architecture

Sound is a vibration in an elastic medium such 
as air, water, most building materials, and the earth. 
(Noise can be defined as unwanted sound, that is, 
annoying sound made by others or very loud sound
which may cause hearing loss.)
An elastic medium returns to its normal state after a 
force is removed.
Pressure is a force per unit area. Sound energy progresses
rapidly,producing extremely small changes in atmospheric
 pressure, and can travel great distances. 
However, each vibrating particle moves only an infinitesimal 
amount to either side of its normal position. 
It “bumps’’ adjacent particles and imparts most of its motion 
and energy to them.A full circuit by a displaced particle is called 
a cycle.  The time required for one complete cycle is called the 
period and the number  of complete cycles per second is 
the frequency of vibration. 
Consequently, the reciprocal of frequency is the period. 
Frequency is measured in cycles per second, the unit for 
which is called the hertz (abbreviated Hz).
A pure tone is vibration produced at a single frequency. 
 depicts the variation in pressure caused by striking a tuning
 fork, which produces an almost pure tone by vibrating 
adjacent air molecules. 
Symphonic music consists of numerous tones at different 
frequencies and pressures (that is, a tone is composed of a 
fundamental frequency with multiples of the fundamental, 
called harmonics). 
 theprongs of the tuning fork alternately compress and 
rarefy adjacent air particles. This cyclical motion causes a 
chain reaction between adjacent air particles so that the 
waves (but not the air particles) propagate away from the tuning fork.