1.
Acoustics is a branch of physics that study the
sound, acoustics concerned with the production, control,
transmission, reception, and effects of sound.
The study of acoustics has been fundamental to many
developments in the arts, science, technology, music, biology,
etc

2.
División of acoustics.
Aero acoustics
Architectural acoustics
Bioacoustics
Biomedical acoustics
Environment noise
Psychoacoustics
Physiological acoustics
Physical acoustics
Speech communication
Structural acoustics
Transduction
Musical acoustics
Underwater acoustics
Nonlinear acoustics

3.
Sound
• Sound is reflected, transmitted, or absorbed by the materials it
encounters.
• Soft surfaces, such as textiles, and bat insulation, tend to absorb sound
waves, preventing them from further motion.
• Hard surfaces, such as ceramic tile, gypsum board, or wood, tend to
reflect sound waves, causing „echo‟. Reverberation is the term used to
describe sound waves that are reflected off of surfaces.
• Dense, massive, materials, such as concrete or brick, tend to transmit
sound waves through the material.
• High frequency sound waves (think of a high whistle) are not capable
of being transmitted through massive, heavy, material.
• Low frequency sound waves (bass) are transmitted through massive
materials.

4.
The human ear is capable of hearing sounds
within a limited range.

5.
Animals have varied hearing ranges

6.
Hearing range of some animals

7.
Hearing range of some animals
• Many animals hear a much wider range of frequencies than
human beings do.
• For example, dog whistles vibrate at a higher frequency than
the human ear can detect, while evidence suggests that
dolphins and whales communicate at frequencies beyond
human hearing (ultrasound).
• Frequency is measured in hertz, or the number of sound
waves a vibrating object gives off per second. The more the
object vibrates, the higher the frequency and the higher the
pitch of the resulting sound.

8.
Decibel levels
• 0 The softest sound a person can hear with normal hearing
• 10 normal breathing
• 20 whispering at 5 feet
• 30 soft whisper
• 50 rainfall
• 60 normal conversation
• 110 shouting in ear
• 120 thunder

9.
Decibel levels
• The human ear's response to sound level is roughly logarithmic (based
on powers of 10), and the dB scale reflects that fact.
•
• An increase of 3dB doubles the sound intensity but a 10dB increase is
required before a sound is perceived to be twice as loud.
• Therefore a small increase in decibels represents a large
increase in intensity.
• For example - 10dB is 10 times more intense than 1dB, while
20dB is 100 times more intense than 1dB.
• The sound intensity multiplies by 10 with every 10dB increase.

10.
Decibel levels
• 130dB - Jack Hammer (at 5ft)
• 120dB - Rock Concert / Pain threshold
• 110dB - Riveter or a Heavy Truck at 50ft
• 90dB - Heavy Traffic (at 5ft)
• 70dB - Department Store or a Noisy Office
• 50dB - Light Traffic
• 30dB - Quiet Auditorium
• 20dB - Faint Whisper (at 5ft)
• 10dB - Soundproof room / anechoic chamber

11.
An anechoic chamber is a space in which
there are no echoes or reverberations.
The surfaces absorb all sound, and reflect none.

12.
Acoustics: sound
• Sound is a mechanical wave and therefore requires a medium in which
it can travel.
• Acoustics is classically divided into sound and vibration.
• Sound refers to waveforms traveling through a fluid medium such as
air
• Vibration describes energy transmitted through denser materials such
as wood, steel, stone, dirt, drywall or anything besides a fluid.
• It is not heard as much as felt, due to its extremely low frequency,
which is below the range of most human hearing.

13.
The speed of sound versus the speed of light
• sound travels at 1130 feet per second at normal room temperature.
• light travels at 299,792,458 meters per second, which is roughly
974,325,489 feet per second (974 million feet per second!!)

14.
Sound Waves:
amplitude & frequency (cycles)

15.
Radio signals: am & fm

16.
Radio signals: am & fm
• „am‟ means: amplitude modulation: the height of each wave changes
• „fm‟ means: frequency modulation: the length of each wave changes
• FM signals have a great advantage over AM signals.
• Both signals are susceptible to slight changes in amplitude.
• With an AM broadcast, these changes result in static. With an FM broadcast, slight
changes in amplitude don't matter -- since the audio signal is conveyed through changes
in frequency, the FM receiver can just ignore changes in amplitude. The result: no static
at all.

17.
Bonded acoustical cotton; recycled cotton, class A non flammable
Melamine Foam Acoustical Panels: fiber free, Class A fire retardant

18.
Fabric wrapped panels provide good acoustical
absorption

19.
Reverberation Time
• Reverberation time refers to the amount of time required for the sound
field in a space to decay 60dB, or to one millionth of the original
power.
• In simple terms this refers to the amount of time it takes for sound
energy to bounce around a room before being absorbed by the
materials and air

20.
Reverberation Time
• Reverberation time is important because it can affect how well you
understand speech, and it can change the way music sounds.
• The effect on speech intelligibility is noticeable in a gymnasium or
arena, where you often can't understand someone who is only 10 or 15
feet away from you

21.
Useful Reflections
• Reflections are an important part of acoustical design for music
performance venues.
• For effective musical acoustics, the reflections have to arrive within
the correct time window, and from the correct direction.

22.
Useful Reflections
• The reflections help to boost the level of acoustic instruments and
human voices in the audience area.
• They also influence timbre and help define the apparent size or
perspective of the instruments.
• The critical time interval we're talking about is a very brief 0.3 seconds

23.
Useful Reflections
• A properly designed acoustical environment provides a good listening
experience for the audience by enhancing the performance or
presentation.
• Even and natural sound coverage, freedom from intruding noise and a
sense of presence from the performer or presenter are all-important
aspects of "good acoustics.“
• Acoustics should be considered very early in the design process and
the aesthetic concept developed in accordance with those requirements

24.
'Stradia': a sound simulation program

25.
Concert halls demand very careful
acoustical analysis

26.
Acoustical Characteristics
1. Liveness
2. Intimacy
3. Fullness
4. Clarity
5. Warmth
6. Brilliance
7. Texture
8. Blend
9. Ensemble

27.
Liveness
Measure of reverberation time

28.
Fullness vs. Clarity
Refers to the amount of
reflected sound relative to
the amount of direct sound

29.
Warmth vs. Brilliance
Warmth increases with
increasing TR for low frequencies

30.
Texture
“Good texture” when at least
five reflections arrive within
60ms of direct sound

31.
Blend and Ensemble
Ability to hear the
entire performing group
on the stage (ensemble) and
in the audience (blend)

32.
Acoustical Design Problems
1. Focusing of sound
2. Echoes
3. Shadows
4. Resonances
5. External noise
6. Double-valued TR

33.
Focusing of Sound
Occurs with use of
parabolic surfaces
either behind performers
or at rear of auditorium

34.
Echoes
Highly reflective flat or
parabolic wall shapes
Flutter echoes from
parallel walls
Standing waves
between parallel walls

35.
Resonances
Parallel walls
Rectangular practice rooms
Singing in the shower

36.
External noise
Box within a box construction
Practice rooms and concert halls
in adjacent areas

37.
Double-valued TR
Playback room with reverberation
Concert halls with side areas

38.
Architectural acoustics is the science of controlling sound in
buildings. Embraces all aspects of acoustical design for all types of
architectural spaces, in order to optimize environments for many functions,
including business, recreation, learning, worship, communication,
broadcasting and entertainment.
The first application of architectural acoustics was in the design of :
•Opera houses
•Concert halls
•Auditoriums
•Radio and television studios
•Classrooms, etc.

39.
Aula Magna (UCV)
Sydney Opera House

40.
Aula Magna, in
“Universidad Central de
Venezuela” it was design
by Carlos Raul
Villanueva
In the 80´s this concert hall
was catalogued like one of
the 5 rooms with better
acoustics of the world.

41.
All the details, materials, forms, elements and the design
were choose for create a good acustical in the space.
For this, Villanueva asked help from some Acustical
consultans: “Bolt, Beranek and Newman Inc”. The selection of
types of wood, the model of the armchairs and services were
carefully chosen.

42.
Even the fabric of the carpet (casimire) was
selected to contribute with the acusticals properties.
The tapestry in Aula Magna has absorption
capacity, when the room is empty does not distort the
sound.
The material of the doors, and some elements
ubicated in the hall are design to prevent the echo and
noise.

43.
The distinguished
element of this famous hall, are
their clouds also called flying
subjects.
This elements were not
in the original design, but
structure of the hall didn´t
For that reason, allow a good acoutic.
Villanueva asked help from
Alexander Calder who was
the designer of this clouds.
The clouds moved to
adapt to the acoustical
requirement, then were fixed in

44.
Building Acoustics: Room for Music
“the most visible and
interesting spaces in
architectural acoustics”
-It is here that the science of
acoustics and the arts
of architecture and
music are blended

45.
Building Acoustics: Room for Music
- The acoustician can only
work indirectly with the
room surfaces that
reflect, diffuse, or
absorb the primal
energy

46.
Building Acoustics: Room for Music
*Concert halls are rooms designed specifically for
music in which the musicians and the audience
occupy the same space.
*In good concert halls the number of seats ranges from
1700 to 2600, with the best halls averaging around
1850.
*Above 2600 seats, the chances of success are much
reduced and the preferred capacity is between 1750
and 2200.

47.
Building Acoustics: Room for Music
There is no division between the stage and the
audience in a concert hall.
The orchestra is positioned on a raised platform,
sometimes with an organ and choir seating behind it.
To attain long reverberation times, the ceilings of
concert halls are high, 15m(50 ft) or more, and
diffusive, with coffered patterns having deep (15
cm or 6 in) fissures.
Side walls are adorned with columns, caryatids,
statuary, and convex shapes that help diffuse the
reflected energy.

48.
Building Acoustics: Room for Music
An opera house is a mix of a legitimate theatre and a
concert hall, which constrains the design more than a
pure concert hall.
In opera, the stage performance rather than the orchestra
is the main attraction
The orchestra is seated in a pit below the stage to
balance the level between the singer and the orchestra.
The conductor, who must be visible to both the orchestra
and the vocalists, stands with his head just at stage level.
Open pits, where the orchestra is open to the audience
with minimal stage overhang, give the best results in large
rooms

49.
Building Acoustics: Room for Music
GENERAL DESIGN PARAMETERS
The audience should feel enveloped or surrounded
by the sound
Sound must have adequate loudness that is evenly
distributed throughout the hall.
Noise from exterior sources and mechanical
equipment must be controlled so that the quietest
instrumental sound can be heard

50.
Building Acoustics: Room for Music
Hall Shape

51.
Building Acoustics: Room for Music
Heavy plaster is the most commonly encountered wall
and ceiling material
Plaster may also be applied directly onto grouted
concrete block or concrete
When wood is used it should be heavy, at least 1”
(25 mm) thick, and be backed with a solid masonry
or concrete.
Wood can be glued directly to concrete block or
concrete walls or applied on furring strips
Floors are constructed of concrete or wood on
concrete

52.
Auditorium
Design

53.
General Design Considerations
1. Visual
2. Ventilation
3. Acoustical
a. seating
b. stage
c. room shape
d. room walls

54.
Control of TR
TR = 0.050 V / A
Where:
TR = reverberation time in second
V = room volume in cubic feet
A = total room absorption in sabins

55.
TR Calculation
A = a1A1 + a2A2 + a3A3 + a4A4 + …
An is one section of absorbent area
an is absorption coefficient
TR = 0.050 V/A

56.
Some Absorption Coefficients
Frequency (Hz)
Material 125 250 500 1000 2000 4000
Concrete/brick 0.01 0.01 0.02 0.02 0.02 0.03
Glass 0.19 0.08 0.06 0.04 0.03 0.02
Plasterboard 0.20 0.15 0.10 0.08 0.04 0.02
Plywood 0.45 0.25 0.13 0.11 0.10 0.09
Carpet 0.10 0.20 0.30 0.35 0.50 0.60
Curtains 0.05 0.12 0.25 0.35 0.40 0.45
Acoustical board 0.25 0.45 0.80 0.90 0.90 0.90

57.
Absorptions (in sabins)
Frequency (Hz)
Material 125 250 500 1000 2000
Unupholstered seat 0.15 0.22 0.25 0.28 0.50
Upholstered seat 3.0 3.1 3.1 3.2 3.4
Adult person 2.5 3.5 4.2 4.6 5.0
Adult/upholstered seat 3.0 3.8 4.5 5.0 5.2

58.
Dekelbaum
Concert Hall
at the
U MD
Smith Center

59.
Dekelbaum Concert Hall (front)

60.
Dekelbaum Concert Hall (rear)

61.
Microphone
configuration
in
concert hall

62.
Loudspeaker
configuration
in home
listening rooms

63.
NOISE
MEASUREMENT
& ABATEMENT

64.
The nature of sound
Sound, a manifestation of vibration, travels in wave patterns through
solids, liquids and gases.
The waves, caused by vibration of the molecules, follow sine functions,
typified by the amplitude and wavelength (or frequency)
Sound waves of equal
amplitude with increasing
frequency from top to
bottom

65.
Sound propagation

66.
Amplitude and wavelength
(period)

67.
Bels and decibels

68.
Sound power and intensity

69.
Sound pressure level

70.
Sound pressure for known sounds

71.
How sound is measured
•Pressure, P, usually Pascals
•Frequency, f, usually Hertz P = 1/f
•Intensity, I, usually W/m2 I = W/A
•Bels, L’, derived from logarithmic ratio L’ = log (Q/Qo)
•Decibels, L, derived from bels L = 10*log (Q/Qo)
E.g. Implications of the decibel scale: doubling sound level
would mean that the sound will increase by 10*log2 = +3dB
Ten times the sound level = 10*log10 = +10dB

72.
Exposure to high sound levels

73.
Reflecting on noise
 “Noise" derived from "nausea," meaning seasickness
 Noise is among the most pervasive pollutants today
 Noise is unavoidable for many machines
 We experience noise in a number of ways
environmental
cause and victim
generated by others “second-hand”
 Noise negatively affects human health and well-being
 The air into which second-hand noise is emitted and
on which it travels is a "commons“, a public good

74.
Noise regulation
Noise regulation includes statutes or guidelines relating to
sound transmission established by national, state or
provincial and municipal levels of government. After a
watershed passage of the U.S. Noise Control Act of
1972[1], the program was abandoned at the federal level,
under President Ronald Reagan, in 1981 and the issue was
left to local and state governments. Although the UK and
Japan enacted national laws in 1960 and 1967 respectively,
these laws were not at all comprehensive or fully
enforceable as to address (a) generally rising ambient noise
(b) enforceable numerical source limits on aircraft and
motor vehicles or (c) comprehensive directives to local
government.

75.
Local noise regulation
 Dr. Paul Herman wrote the first comprehensive noise codes in 1975 for Portland, Oregon with
funding from the EPA (Environmental Protection Agency) and HUD (Housing and Urban
Development). The Portland Noise Code became the basis for most other ordinances for major
U.S. and Canadian metropolitan regions.[18]
 Most city ordinances prohibit sound above a threshold intensity from trespassing over property line
at night, typically between 10 p.m. and 6 a.m., and during the day restricts it to a higher sound
level; however, enforcement is uneven. Many municipalities do not follow up on complaints. Even
where a municipality has an enforcement office, it may only be willing to issue warnings, since
taking offenders to court is expensive.
 The notable exception to this rule is the City of Portland Oregon which has instituted an aggressive
protection for its citizens with fines reaching as high at $5000 per infraction, with the ability to cite a
responsible noise violator multiple times in a single day.
 Many conflicts over noise pollution are handled by negotiation between the emitter and the
receiver. Escalation procedures vary by country, and may include action in conjunction with local
authorities, in particular the police. Noise pollution often persists because only five to ten percent of
people affected by noise will lodge a formal complaint. Many people are not aware of their legal
right to quiet and do not know how to register a complaint

76.
Aircraft noise
FA-18 Hornet
breaking sound
barrier

77.

Adding noise sources and
subtracting background noise
10 log 2
= 3 dB

78.
Chart method – adding decibels

79.
Chart method – subtracting background noise

80.
Power ratio
and dB
http://www.phys.unsw.edu.
au/jw/dB.html

81.
Sound and human hearing
People generally hear sounds
between the “threshold of hearing”
and the “threshold of pain”
In terms of pressure,
this is 20 μPa – 100 Pa
The decibel scale was developed from this fact
and makes numbers more manageable
The decibel scale generally ranges from
approximately 0 to 130

82.
How Sound is Heard

83.
Human hearing and Frequency
0 16 Hz 20 kHz 5 MHz

84.
Sound and human hearing – Frequency
Humans are less sensitive to low frequency
sound and more sensitive to high frequency
sound. Therefore, sometimes the dB scale is
adjusted to take this into account:
A-weighting (db(A)): adjusts overall scale so it
better matches what the human ear would hear
C-weighting (dB(C)): adjusts scale for loud or
low frequency sounds
B-weighting (dB(B)): adjusts by factors that are
“in between” the A-weighted factors and C-
weighted factors (rarely used)

85.
The filters used for dBA and dBC
The most widely used sound level filter is the A scale, which
roughly corresponds to the inverse of the 40 dB (at 1 kHz)
equal-loudness curve. The sound level meter is thus less
sensitive to very high and very low frequencies. Measurements
made on this scale are expressed as dBA. The C scale (in dBC)
is practically linear over several octaves and is thus suitable
for subjective measurements only for very high sound levels.

86.
Loudness in phons
The phon is related to dB by the psychophysically measured
frequency response. Phons = dB at 1 kHz. For other frequencies,
the phon scale is determined by loudness experience by humans.

87.
Loudness in sones
The sone is derived from psychophysical tests where
humans judge sounds to be twice as loud. This relates
perceived loudness to phons. A sone is 40 phons. A
10 dB increase in sound level corresponds to a perceived
doubling of loudness. So that approximation is used in the
definition of the phon: 0.5 sone = 30 phon, 1 sone =
40 phon, 2 sone = 50 phon, 4 sone = 60 phon, etc.

88.
Other descriptors of sound
Equivalent sound level – the level of sound that has
the same acoustical energy as does a time-varying
sound over a stated time period.
Percentile sound level – the sound level exceeded “n”
percent of the observation time interval.
Day-night average sound level – the equivalent sound
level for a 24-h period that incorporates a decibel
penalty during night hours.

89.
Typical suburban sound and their levels

90.
Major transportation sources of
noise pollution: rail, road, and air

91.
Rail Noise: A Case Study
The city of Ames, Iowa, began operation of three
automated horn warning systems (AHS) in September
of 1998. These systems were installed after nearby
residents repeatedly expressed concerns over the
disturbance created by the loud train horns.
The automated horn system provides a similar audible
warning to motorists and pedestrians by using two
stationary horns mounted at the crossing. Each horn
directs its sound toward the approaching roadway. The
horn system is activated using the same track signal
circuitry as the gate arms and bells located at the
crossing.

92.
Train Horn Noise Reduction
Sound Level Train Horn AHS Horn Reduction
(dBA) Area (acres) Area (acres)
> 70 265 37 86%
> 80 171 5 97%
> 90 31 <1 98%

93.
Intersection of
70 dBA railroad with
North Dakota Avenue:
A graphical depiction
80 dBA of the reduction
90 dBA
Before
70 dBA
80 dBA 90 dBA
After

94.
Ames Train Horn Noise Survey

95.
Roadway Noise
• An example of a “line source” of noise
pollution (as opposed to a “point source”)
• Level of noise is a function of volume,
type of vehicle, and speed

96.
Roadway Noise - Solutions
• Regulations limit the amount of noise
some vehicles can produce
• Some regulations require vehicles to be
properly operated and maintained
• Despite regulations, the noise levels are
usually only reduced by 5 to 10 dBA

97.
Roadway Noise - Solutions
Barriers
•Buffer zones
•Earth berms/wooden fences/concrete walls
•Vegetation (if dense enough)

98.
Aesthetic noise barrier:
Highway in Melbourne, Australia

99.
Roadway Noise - Solutions
Pavement type
Certain asphalts, such as those containing
rubber or stone, can be less noisy than other
pavements.
However, some studies have shown the
reduction in noise is only a few decibels, not
enough to be significant.
More research is needed before pavement
type can be an effective noise-reducing
technique

100.
Airport Noise
Noise contours around
an airport calculated
using INM (Integrated
Noise Modeling) based
on previous noise
measurements
55 - 60 dB = Light blue
60 - 70 dB = Dark blue
70 - 75 dB = Red
75 - 80 dB = Green
80 - 85 dB = Yellow
> 85 dB = Pink

101.
Airport Noise

102.
Other sources of noise pollution that
need to be addressed
• Boat noise,
especially jet skis
• Construction noise
• Snow mobiles
• Industry