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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
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
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.
The human ear is capable of hearing sounds
        within a limited range.
Animals have varied hearing ranges
Hearing range of some animals
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.
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
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.
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
An anechoic chamber is a space in which
    there are no echoes or reverberations.
The surfaces absorb all sound, and reflect none.
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.
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!!)
Sound Waves:
amplitude & frequency (cycles)
Radio signals: am & fm
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.
Bonded acoustical cotton; recycled cotton, class A non flammable
Melamine Foam Acoustical Panels: fiber free, Class A fire retardant
Fabric wrapped panels provide good acoustical
                absorption
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
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
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.
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
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
'Stradia': a sound simulation program
Concert halls demand very careful
       acoustical analysis
Acoustical Characteristics

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

Measure of reverberation time
Fullness vs. Clarity
 Refers to the amount of
 reflected sound relative to
 the amount of direct sound
Warmth vs. Brilliance




     Warmth increases with
increasing TR for low frequencies
Texture




“Good texture” when at least
five reflections arrive within
    60ms of direct sound
Blend and Ensemble
     Ability to hear the
 entire performing group
on the stage (ensemble) and
  in the audience (blend)
Acoustical Design Problems
     1. Focusing of sound
     2. Echoes
     3. Shadows
     4. Resonances
     5. External noise
     6. Double-valued TR
Focusing of Sound

    Occurs with use of
     parabolic surfaces
 either behind performers
  or at rear of auditorium
Echoes
Highly reflective flat or
 parabolic wall shapes

  Flutter echoes from
     parallel walls

    Standing waves
 between parallel walls
Resonances
      Parallel walls

Rectangular practice rooms


  Singing in the shower
External noise
Box within a box construction

Practice rooms and concert halls
        in adjacent areas
Double-valued TR
Playback room with reverberation

 Concert halls with side areas
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.
Aula Magna (UCV)
Sydney Opera House
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.
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.
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.
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
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
Building Acoustics: Room for Music


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

Hall Shape
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
Auditorium
 Design
General Design Considerations

       1. Visual
       2. Ventilation
       3. Acoustical
            a. seating
            b. stage
            c. room shape
            d. room walls
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
TR Calculation
A = a1A1 + a2A2 + a3A3 + a4A4 + …

 An is one section of absorbent area
 an is absorption coefficient

     TR = 0.050 V/A
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
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
Dekelbaum
Concert Hall
   at the
   U MD
Smith Center
Dekelbaum Concert Hall (front)
Dekelbaum Concert Hall (rear)
Microphone
configuration
      in
 concert hall
Loudspeaker
 configuration
     in home
listening rooms
NOISE
MEASUREMENT
& ABATEMENT
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
Sound propagation
Amplitude and wavelength
        (period)
Bels and decibels
Sound power and intensity
Sound pressure level
Sound pressure for known sounds
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
Exposure to high sound levels
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
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.
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
Aircraft noise




            FA-18 Hornet
            breaking sound
            barrier



Adding noise sources and
subtracting background noise


                        10 log 2
                        = 3 dB
Chart method – adding decibels
Chart method – subtracting background noise
Power ratio
   and dB

http://www.phys.unsw.edu.
au/jw/dB.html
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
How Sound is Heard
Human hearing and Frequency




0     16 Hz    20 kHz    5 MHz
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)
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.
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.
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.
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.
Acoustic, Sound and Noise Control
Typical suburban sound and their levels
Acoustic, Sound and Noise Control
Major transportation sources of
noise pollution: rail, road, and air
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.
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%
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
Ames Train Horn Noise Survey
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
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
Roadway Noise - Solutions


Barriers
•Buffer zones

•Earth berms/wooden fences/concrete walls

•Vegetation (if dense enough)
Aesthetic noise barrier:
Highway in Melbourne, Australia
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
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
Airport Noise
Other sources of noise pollution that
       need to be addressed

 • Boat noise,
   especially jet skis

 • Construction noise

 • Snow mobiles

 • Industry

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Acoustic, Sound and Noise Control

  • 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)
  • 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
  • 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
  • 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
  • 61. Microphone configuration in concert hall
  • 62. Loudspeaker configuration in home listening rooms
  • 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
  • 68. Sound power and intensity
  • 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.
  • 90. Typical suburban sound and their levels
  • 92. Major transportation sources of noise pollution: rail, road, and air
  • 93. 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.
  • 94. 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%
  • 95. 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
  • 96. Ames Train Horn Noise Survey
  • 97. 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
  • 98. 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
  • 99. Roadway Noise - Solutions Barriers •Buffer zones •Earth berms/wooden fences/concrete walls •Vegetation (if dense enough)
  • 100. Aesthetic noise barrier: Highway in Melbourne, Australia
  • 101. 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
  • 102. 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
  • 104. Other sources of noise pollution that need to be addressed • Boat noise, especially jet skis • Construction noise • Snow mobiles • Industry