Presentation Acoustics 06

7/28/2019 Presentation Acoustics 06

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Acoustics

a science that deals with the production, control,

transmission, reception, and effects of sound. definition from the Merriam-Webster Online Dictionary

acoustics is addressed in the text Interior Construction& Detailing on pages 259 - 282. These pages will be

used for questions on Exam 2.


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Sound is reflected, transmitted, or absorbed by the materials it

encounters.

Soft surfaces, such as textiles, and batt 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.


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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.


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Animals have varied hearing

ranges


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Hearing range of some animals


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Many animals hear a much wider range of frequencies thanhuman beings do.

For example, dog whistles vibrate at a higher frequency than thehuman 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 avibrating object gives off per second. The more the object

vibrates, the higher the frequency and the higher the pitch of theresulting sound.


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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


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Decibel levels

The human ear's response to sound level is roughly logarithmic (based onpowers of 10), and the dB scale reflects that fact.

An increase of 3dB doubles the sound intensity but a 10dB increase isrequired before a sound is perceived to be twice as loud.

Therefore a small increase in decibels represents a large increase inintensity.

For example - 10dB is 10 times more intense than 1dB, while 20dBis 100 times more intense than 1dB.

The sound intensity multiplies by 10 with every 10dB increase.


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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


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An anechoic chamber is a space in which

there are no echoes or reverberations.The surfaces absorb all sound, and reflect none.


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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 asair

Vibration describes energy transmitted through denser materials

such as wood, steel, stone, dirt, drywall or anything besides a fluid.

It is not heardas much as felt, due to its extremely low frequency,which is below the range of most human hearing.


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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!!)


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Sound Waves:

amplitude & frequency (cycles)


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Radio signals: am & fm


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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.


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Bonded acoustical cotton; recycled cotton, class A non flammable

Melamine Foam Acoustical Panels: fiber free, Class A fire retardent


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Fabric wrapped panels provide good acoustical absorption


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Advanced Study of Acoustics

Acoustics is the subject of formal, advanced study, including the

fields of engineering, architecture, and psychology.

For example, the School of Architecture at Rensselaer Polytechnic

Institute offers a formal program for a Masters of Science degree inBuilding Science (Concentration in Architectural Acoustics)


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The Graduate Program in Architectural Acoustics offers an intense

curriculum in acoustics for effectively shaping sonic environments to

achieve optimum acoustic performance and sound quality.

The Program offers studies toward both Master of Science andPh.D. degrees.

Further doctoral degree studies offer a unique program in

architectural acoustics, providing the knowledge for next-generation

acousticians involved in room acoustics, psychoacoustics, acousticand vibrationmeasurement techniques, and sound reinforcement.


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Researchers in the acoustics program in the School of Architecture

are investigating how the design of a classroom can affect how

easily students hear.

The researchers believe that if more attention is paid to classroomacoustics when designing the space, students will have an easier

time learning and understanding what's going on.


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Research of this kind could lead to the development of new

standards for classroom acoustics.

Regulators for the Americans with Disabilities Act are currently

working on such standards, which exist already in countries such asGermany and the United Kingdom.


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an example of books dedicated to the study of architecture

and acoustics
http://www.acentech.com/AcousCDdesc.htmhttp://www.acentech.com/AcousBook.htm


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Music and Drama Theater Acoustics

The acoustical characteristics of a venue for the live performance of

music or drama are an important part of the audience experience.

For music performance, the room becomes part of the instrument,

helping define the character of the musical sound that the audiencehears.


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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


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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 or15 feet away from you


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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.


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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


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Acoustics Consultants May Provide:

Architectural Acoustics

Sound Isolation Testing

Impact Isolation Testing

Mechanical (HVAC) System Noise and Vibration Environmental/Community Noise Assesment

Computer & Physical Acoustical Modeling

Field Testing

Industrial Noise Control

Sound Masking Systems Desig


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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 anda sense of presence from the performer or presenter are all-

important aspects of "good acoustics."


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Acoustics should be considered very early in the design process

and the aesthetic concept developed in accordance with those

requirements.


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'Stradia': a sound simulation program


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Sound ray diagram of New National Theatre, Tokyo (May 1986


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Concert halls demand very careful

acoustical analysis


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The Sydney Opera House concert hall

building designed by Jorn Utzon


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Presentation Acoustics 06