Acoustics plays an important role in the sound ergonomics due to which sound can be distributed equally to entire hall. the following slide gives an overview of the factors of acoustics and its remedies.

1. Gandhinagar Institute of Technology
Active Learning Assignment
Subject :-Physics(2110011)
Semester 2
Topic:- Factors Affecting Acoustics Of Buildings & Their
Remedies
Batch:- H2
Department : - Mechanical
Prepared By:- Burhanuddin Kapadia (170120119026)
Guided by:- Prof. Nirav Pandya

2. CONTENT
• Acoustics
• Factors affecting acoustics of building and its remedies
i. Reverberation Time
ii. Loudness
iii. Focussing
iv. Echo
v. Echelon effect
vi. Resonance
vii. Noise
• Condition for a good acoustics
• Reference

3. ACOUSTICS
• Acoustics is a branch of physics which deals with the generation, propogation,
reception, and analysis of sound waves.
• Accordingly, the science of acoustics spreads across many facets of human society
music, medicine, architecture, industrial production, warfare and more.
• Acoustics is defined by ANSI/ASA S1.1-2013 as
 Science of sound, including its production, transmission, and effects, including biological and psychological
effects.
• The fundamental acoustical process.

4. ACOUSTICS
• The word "acoustic" is derived from the Greek word (ἀκουστικός akoustikos).
• Meaning "of or for hearing, ready to hear"
• (ἀκουστός akoustos), "heard, audible", in turn derives from the verb (ἀκούω akouo), "I
hear".
• The Latin synonym is "sonic", after which the term sonics used to be a synonym for
acoustics and later a branch of acoustics.
• Frequencies above and below the audible range are called "ultrasonic" and "infrasonic",
respectively.

5. FACTORS
• There are many differences in the acoustical properties of buildings or rooms.
• Some are quiet enough to hear a pin drop from one end to the other.
• In others, you almost have to shout to be heard barely across the room.
• Still others are noisy and filled with echo’s.
• There are many factors that determine the acoustical properties of buildings or rooms
within buildings.
• Factors that acoustics of a building are reverberation time, loudness, focusing, Echelon
effect, resonance, noise and Echo.

6. FACTORS
Some
Basic
factor
s

7. FACTORS

8. REVEBREATION TIME
• Persistence or prolongation of sound is known as Revebreation time.
• When is too large in a hall, an overlapping of sounds and echo results.
• If the reverberation is very less, the loudness will be insufficient, sound disappear quickly
and become inaudible.
• A satisfactory value = optimum reverberation time.
• Classrooms reverberation times in the range of 0.4-0.6 seconds.

9. WHAT IS A DESIRABLE REVERBERATION TIME?

10. CALCULATION OF REVERBERATION OF TIME
For dimension in meters For dimension in feet

11. REMEDIES
• The Revebreation time can be maintained at an optimum value by adopting following ways:
i. By providing Windows and openings
ii. By having full capacity of audience in hall or room
iii. By using heavy curtains with folds
iv. By covering the floor with carpets
v. By decorating walls with wallpapers
vi. By covering ceiling with good sound absorbing materials like felt, fibre board, false roofing, etc.

12. LOUDNESS

13. REMEDIES
• If the loudness of the sound is not adequate, it can be increased by adopting the
following ways:
i. By using suitable absorbents at places where noise is high.
ii. By constructing low ceilings for the reflection of sound towards listener.
iii. By using large sounding boards behind the speaker and facing the audience.
iv. By using public address system like loudspeaker.

14. FOCUSSING
• Sound waves falling on the concave surface or curved surfaces of the building after
reflection get focused to a point.
• Intensity of sound is maximum at those points and zero at the other points and this is
called as the focusing effect.
• Those surfaces are known as dead space.
• And, there will be an uneven distribution of sound intensity.
• Equal distribution of sound in the hall is achieved if there is no curved surface in the hall.

15. REMEDY
• Curved surfaces can be avoided.
• If curved surfaces are present, they should be covered with suitable sound absorbing
materials.

16. ECHO

17. REMEDY
• An echo can be avoided by covering long distance walls and high ceiling with suitable sound-absorbing material.
• The human ear cannot distinguish echo from the original direct sound if the delay is less than 1/10 of a second.
• The velocity of sound in dry air is approximately 343 m/s at a temperature of 25 °C.
• Therefore, the reflecting object must be more than 17.2m from the sound source for echo to be perceived by a
person located at the source.
• When a sound produces an echo in two seconds, the reflecting object is 343m away.
• In nature, canyon walls or rock cliffs facing water are the most common natural settings for hearing echoes.
• The strength of echo is frequently measured in dB sound pressure level (SPL) relative to the directly
transmitted wave.
• Echoes may be desirable (as in sonar) or undesirable (as in telephone systems).

18. ECHELON EFFECT
• The process of combination of multiple echoes and forming of a new sound is known as
echelon effect.
• A set of railings or rectangular surfaces is said to produce echelon effect.
• This echelon effect affects the original quality of sound.

19. REMEDY
• The effect to avoid echelon effect is to cover such surfaces with sound absorbing
materials.

20. RESONANCE
• Acoustic resonance is a phenomenon where acoustic systems amplify sound waves whose frequency matches one of its own
natural frequencies of vibration.
• An acoustically resonant object usually has more than one resonance frequency, especially at harmonics of the strongest
resonance.
• It will easily vibrate at those frequencies, and vibrate less strongly at other frequencies.
• Acoustic resonance is an important consideration for instrument builders, as most acoustic instruments use resonators, such
as the strings and body of a violin, the length of tube in a flute, and the shape of a drum membrane.
• Acoustic resonance is also important for hearing.
• For example, resonance of a stiff structural element, called the basilar membrane within the cochlea of the inner
ear allows hair cells on the membrane to detect sound
• Like mechanical resonance, acoustic resonance can result in catastrophic failure of the vibrator.

21. REMEDY
• The resonance can be avoided by fixing the window panels properly
• Any other vibrating object which may produce resonance can be placed over a suitable
sound absorbing materials.

22. NOISE
• Sound which irritates the ear or unwanted sound is called noise.
• Noises produced are three types:
i. Air Borne noise
ii. Structure-borne noise
iii. Inside noise
• The noise coming from doors windows are categorized in air-borne noise.
• The noise conveyed by the structure of building is called structure borne noise.
• The noise produced inside the room, due to indoor machineries like air conditioner,
generators, fans, etc is categorized under inside noise.

23. REMEDIES
• For external noise:
i. The hall or room can be made air conditioned.
ii. By using doors and windows with proper sound absorbing material between frames and panel.
• For structure-borne noise:
i. By using double walls with air space between them.
ii. By using anti vibration mounts.
iii. By covering floors and walls with proper sound absorbing material.
• For Internal noise:
i. The sound producing machineries can be placed over sound absorbing materials like carpet, pads, wood, felt,
etc
ii. By using curtains.

24. ACOUSTIC CONDITION OF A BUILDING
• The quality of sound and loudness should be uniform throughout the entire hall or
auditorium.
• There should not be any overlapping of sound.
• The presence or absence of audience should not affect the quality of sound.
• Resonance effect should be avoided.
• The hall should have a proper reverberation time.
• The external noise should not disturb the proceeding it the hall.
• There should not be any echelon effect.

25. REFERENCE
• http://infloria.com/factors-affecting-acoustics-of-building-and-their-remedies/
• https://www.ehow.com/info_8050786_factors-affecting-acoustics-buildings.html
• https://en.wikipedia.org/wiki/Acoustics
• http://getseminar.in/showthread.php?tid=17502
• http://hyperphysics.phy-astr.gsu.edu/hbase/Acoustic/revtim.html
• https://www.britannica.com/science/loudness
• http://fascinatingphysics.blogspot.in/2009/08/acoustics-of-auditorium.html