Architectural Acoustics
• Factors Affecting Architectural Acoustics
1.Reverberation Time
• When the reverberation time is too high, the sound produced by
the speaker will persist for a long period of time.
• Similarly ,when the reverberation time is low, sound dies quickly
and becomes inaudible in a short amount of time.
• In order to improve the sound, reverberation time of a hall should
be increased to an optimum value.
Remedies :-
• Decreasing total absorption coefficient of the wall
• Placing sound reflection boards inside a hall

2. Loudness
• Reverberation time of a hall is directly proportional to loudness.
• Low loudness results in existence of sound for a shorter period
while high loudness results in existence of sound for a longer
period.
• Therefore sound produced by the speaker should be within
audible range.
Remedies :-
• Placing sound absorbing boards to reduce loundness
• Placing sound reflecting boards to increase loudness

3. Echelon Effect
• Unwanted sounds are produced when people walk on
staircase or floors or hard paved paths due to poor finishing
of the floor surface, structural effects, etc.
• The above mentioned unwanted sound are termed as
‘echelon effect’ .
Remedies :-
• Finishing the floors or stairs very finely.
• Using carpet to caver floors and stairs.

4. Structure-Borne Sound
• Sound waves generated inside a hall are known as structure-borne
sound.
• They are produced due to apparent motion of benches &
footsteps & propagated through walls and floors.
Remedies :-
• Using rigid structures so as to rest the vibrations.
• Introducing discontinuities in the path of sound.
• Converting floor and ceilings with suitable sound absorbing
materials & anti-vibration mouths.

5. Echo
• If the time interval between direct sound and reflected
sound is less than 1/15 of a second, the reflected sound is
helpful in incresing loudness.
• But if the time interval is less than that, then the sound
arrives later and will cause confusion.
Remedies :-
• To prevent unnecessary reflection of sound.
• Covering long distance walls and ceilings with suitable sound
absorbing materials.

6. Focusing due to walls and ceilings
• Sound produced by speaker undergoes multiple reflections at
ceilings and walls.
• Reflected sounds from ceilings and walls should not be focused on
particular point, rather it should be distributed throughout a hall.
• Generally a plane surface reflects sound uniformly but a curved
surface does not. So reflection of sound from a curved surface
produces a harmful effect.
Remedies :-
• Radius of curvature of ceilimg should be kept twice the height of
the building
• Distribution of sound waves from a concave surface should be
made uniform

7. Resonance within a building
• Sound waves get amplifies when the frequency of vibration
of air particles matches with the hall’s natural frequency of
vibration.
• Thus, it results in an unwanted sound effect in side a hall.
Remedies :-
• Model-Hall or a model auditoriun should be kept inside a
vessel which contains water.
• The water-wave particle movememnts are studies and are
used for the construction of actual hall or auditorium.