Space Technology » Acoustics http://www.contour2002.org All about space research and technology Sun, 28 Aug 2011 02:49:50 +0000 en hourly 1 http://wordpress.org/?v=3.1 Diffusion (acoustics) – Introductionhttp://www.contour2002.org/article/diffusion-acoustics-introduction http://www.contour2002.org/article/diffusion-acoustics-introduction#comments Sat, 30 Jul 2011 14:49:43 +0000 http://www.contour2002.org/article/diffusion-acoustics-introduction

Diffusion, in acoustics and architectural engineering, is the efficacy by which sound energy is spread evenly in a given environment. A perfectly diffusive sound space is one that has certain key acoustic properties which are the same anywhere in the space. A non-diffuse sound space would have considerably different reverberation time as the listener moved around the room. Virtually all spaces are non-diffuse. Spaces which are highly non-diffuse are ones where the acoustic absorption is unevenly distributed around the space, or where two different acoustic volumes are coupled. The diffusiveness of a sound field can be measured by taking reverberation time measurements at a large number of points in the room, then taking the standard deviation on these decay times. Alternately, the spatial distribution of the sound can be examined. Small sound spaces generally have very poor diffusion characteristics at low frequencies due to room modes.

Adapted from the Wikipedia article Diffusion (acoustics), under the G. N. U. Free Documentation License. Please also see http://en.wikipedia.org/wiki

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]]> http://www.contour2002.org/article/diffusion-acoustics-introduction/feed 0 Room acoustics – Reverberation of the roomhttp://www.contour2002.org/article/room-acoustics-reverberation-of-the-room http://www.contour2002.org/article/room-acoustics-reverberation-of-the-room#comments Wed, 13 Jul 2011 02:51:57 +0000 http://www.contour2002.org/article/room-acoustics-reverberation-of-the-room AcousticsAfter determining the best dimensions of the room, using the modal density criteria, the next step is to find the correct reverberation time. The reverberation time depends on the use of the room. Times about 1.5 to 2 seconds are needed for opera theaters and concert halls. For broadcasting & recording studios and conference rooms, [...]No related posts.]]>

After determining the best dimensions of the room, using the modal density criteria, the next step is to find the correct reverberation time. The reverberation time depends on the use of the room. Times about 1.5 to 2 seconds are needed for opera theaters and concert halls. For broadcasting & recording studios and conference rooms, values under one second are frequently used. The recommended reverberation time is always a function of the volume of the room. Several authors give their recommendations A good approximation for Broadcasting Studios and Conference Rooms is: TR[1khz] = [0,4 log (V+62)] – 0,38 TR in seconds and V=volume of the room in m3 The ideal RT must have the same value at all frequencies from 30 to 12,000 Hz. Or, at least, it is acceptable to have a linear rising from 100% at 500 Hz to 150 % down to 62 Hz

In order to get the calculated RT in a room, several acoustics materials can be used as described in several books , A valuable simplification of the task was proposed by Oscar Bonello in 1979 It consists of using standard acoustic panels of 1 m2 hung from the walls of the room (only if the panels are parallel). These panels use a combination of three Helmholtz resonators and a wooden resonant panel. This system gives a large acoustic absorption at low frequencies (under 500 Hz) and reduces at high frequencies to compensate for the typical absorption by people, lateral surfaces, ceilings, etc.

==Compare

*Noise control

*Sound proofing

Category:Acoustics

el:Ακουστική χ&

Acoustics
#974;ρων

de:Raumakustik

nl:Zaalakoestiek
Adapted from the Wikipedia article Room acoustics, under the G. N. U. Free Documentation License. Please also see http://en.wikipedia.org/wiki

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]]> http://www.contour2002.org/article/room-acoustics-reverberation-of-the-room/feed 0 Transient (acoustics) – Sonarhttp://www.contour2002.org/article/transient-acoustics-sonar http://www.contour2002.org/article/transient-acoustics-sonar#comments Sat, 09 Jul 2011 14:49:53 +0000 http://www.contour2002.org/article/transient-acoustics-sonar AcousticsTransient is often used by sonar operators to enter large numbers of crit strings, referring to sudden, unnatural changes in the acoustic environment. This is usually caused by an unnaturally fast moving object. It is most often applied for military use, referring to unexpected sounds emanating from another vessel such as operating machinery, a metal [...]No related posts.]]>

Transient is often used by sonar operators to enter large numbers of crit strings, referring to sudden, unnatural changes in the acoustic environment. This is usually caused by an unnaturally fast moving object. It is most often applied for military use, referring to unexpected sounds emanating from another vessel such as operating machinery, a metal hatch being slammed, or the flooding and pressurization of torpedo or vertical launch tubes.

Category:Acoustics

Category:Sonar

de:Einschwingvorgang

pl:Transjent

Adapted from the Wikipedia article Transient (acoustics), under the G. N. U. Free Documentation License. Please also see http://en.wikipedia.org/wiki

Acoustics

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]]> http://www.contour2002.org/article/transient-acoustics-sonar/feed 0 Journal of Computational Acoustics – Introductionhttp://www.contour2002.org/article/journal-of-computational-acoustics-introduction http://www.contour2002.org/article/journal-of-computational-acoustics-introduction#comments Fri, 08 Jul 2011 14:50:59 +0000 http://www.contour2002.org/article/journal-of-computational-acoustics-introduction AcousticsJournal of Computational Acoustics (JCA) is a scientific journal in the field of computational acoustics, covering ocean, seismo- and aeroacoustics, as well as computational methods and supercomputing. It was founded in 1993 and is published three times a year by World Scientific Publishing. Adapted from the Wikipedia article Journal of Computational Acoustics, under the G. [...]No related posts.]]>

Journal of Computational Acoustics (JCA) is a scientific journal in the field of computational acoustics, covering ocean, seismo- and aeroacoustics, as well as computational methods and supercomputing. It was founded in 1993 and is published three times a year by World Scientific Publishing.

Adapted from the Wikipedia article Journal of Computational Acoustics, under the G. N. U. Free Documentation License. Please also see http://en.wikipedia.org/wiki

Acoustics

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]]> http://www.contour2002.org/article/journal-of-computational-acoustics-introduction/feed 0 Architectural acoustics – Interior space acousticshttp://www.contour2002.org/article/architectural-acoustics-interior-space-acoustics http://www.contour2002.org/article/architectural-acoustics-interior-space-acoustics#comments Wed, 06 Jul 2011 14:52:52 +0000 http://www.contour2002.org/article/architectural-acoustics-interior-space-acoustics AcousticsThis is the science of controlling a room’s surfaces based on sound absorbing and reflecting properties. Excessive reverberation time, which can be calculated, can lead to poor speech intelligibility. Sound reflections create standing waves that produce natural resonances that can be heard as a pleasant sensation or an annoying one. Reflective surfaces can be angled [...]No related posts.]]>

This is the science of controlling a room’s surfaces based on sound absorbing and reflecting properties. Excessive reverberation time, which can be calculated, can lead to poor speech intelligibility.

Sound reflections create standing waves that produce natural resonances that can be heard as a pleasant sensation or an annoying one. Reflective surfaces can be angled and coordinated to provide good coverage of sound for a listener in a concert hall or music recital space. To illustrate this concept consider the difference between a modern large office meeting room or lecture theater and a traditional classroom with all hard surfaces.

Interior building surfaces can be constructed of many different materials and finishes. Ideal acoustical panels are those without a face or finish material that interferes with the acoustical infill or substrate. Fabric covered panels are one way to heighten acoustical absorption. Finish material is used to cover over the acoustical substrate. Mineral fiber board, or Micore, is a commonly used acoustical substrate. Finish materials often consist of fabric, wood or acoustical tile. Fabric can be wrapped around substrates to create what is referred to as a “pre-fabricated panel” and often provides the good noise absorption if laid onto a wall. Prefabricated panels are limited to the size of the substrate ranging from 2′x 4′ to 4′ x 10′. Fabric retained in a wall-mounted perimeter track system, is referred to as “on-site acoustical wall panels” This is constructed by framing the perimeter track into sh

Acoustics
ape, infilling the acoustical substrate and then stretching and tucking the fabric into the perimeter frame system. On-site wall panels can be constructed to accommodate door frames, baseboard, or any other intrusion. Large panels (generally, greater than 50 square feet) can be created on walls and ceilings with this method. Wood finishes can consist of punched or routed slots and provide a natural look to the interior space, although acoustical absorption may not be great.

There are three ways to improve workplace acoustics and solve workplace sound problems – the ABCs.

*A = Absorb {via drapes, carpets, ceiling tiles, etc.)

*B = Block (via panels, walls, floors, ceilings and layout)

*C = Cover-up (via sound masking)

While all three of these are recommended to achieve optimal results, C = Cover-up by increasing background sound produces the most dramatic improvement in speech privacy – with the least disruption and typically the lowest cost.

Adapted from the Wikipedia article Architectural acoustics, under the G. N. U. Free Documentation License. Please also see http://en.wikipedia.org/wiki

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]]> http://www.contour2002.org/article/architectural-acoustics-interior-space-acoustics/feed 0 Good Acoustics – Personnelhttp://www.contour2002.org/article/good-acoustics-personnel http://www.contour2002.org/article/good-acoustics-personnel#comments Sun, 03 Jul 2011 14:50:35 +0000 http://www.contour2002.org/article/good-acoustics-personnel Acoustics*C.J. Snare – vocals, keyboards *Bill Leverty – guitars *Michael Foster – drums *Perry Richardson – bass guitar Category:FireHouse albums Category:1996 compilation albums Category:Epic Records compilation albums pt:Good AcousticsAdapted from the Wikipedia article Good Acoustics, under the G. N. U. Free Documentation License. Please also see http://en.wikipedia.org/wiki No related posts.No related posts.]]>

*C.J. Snare – vocals, keyboards

*Bill Leverty – guitars

*Michael Foster – drums

*Perry Richardson – bass guitar

Category:FireHouse albums

Category:1996 compilation albums

Category:Epic Records compilation albums

pt:Good Acoustics
Adapted from the Wikipedia article Good Acoustics, under the G. N. U. Free Documentation License. Please also see http://en.wikipedia.org/wiki

Acoustics

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]]> http://www.contour2002.org/article/good-acoustics-personnel/feed 0 Cyber Acoustics – Introductionhttp://www.contour2002.org/article/cyber-acoustics-introduction http://www.contour2002.org/article/cyber-acoustics-introduction#comments Sat, 02 Jul 2011 02:51:41 +0000 http://www.contour2002.org/article/cyber-acoustics-introduction AcousticsCyber Acoustics is the name of a company that produces audio equipment, primarily for computers. Their products are widely sold and distributed across Canada, USA, France, UK, Australia and Spain. Cyber Acoustics is often abbreviated “CA”. Cyber Acoustics dates back to the mid 1980s. Adapted from the Wikipedia article Cyber Acoustics, under the G. N. [...]No related posts.]]>

Cyber Acoustics is the name of a company that produces audio equipment, primarily for computers. Their products are widely sold and distributed across Canada, USA, France, UK, Australia and Spain. Cyber Acoustics is often abbreviated “CA”. Cyber Acoustics dates back to the mid 1980s.

Adapted from the Wikipedia article Cyber Acoustics, under the G. N. U. Free Documentation License. Please also see http://en.wikipedia.org/wiki

Acoustics

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]]> http://www.contour2002.org/article/cyber-acoustics-introduction/feed 0 Applied mechanics – Major topics of applied mechanicshttp://www.contour2002.org/article/applied-mechanics-major-topics-of-applied-mechanics http://www.contour2002.org/article/applied-mechanics-major-topics-of-applied-mechanics#comments Thu, 30 Jun 2011 02:52:24 +0000 http://www.contour2002.org/article/applied-mechanics-major-topics-of-applied-mechanics Mechanics* Acoustics * Analytical mechanics * Computational mechanics * Contact mechanics * Continuum mechanics * Dynamics * Elasticity * Experimental mechanics * Fatigue * Finite element method * Fluid mechanics * Fracture mechanics * Mechanics of materials * Mechanics of structures * Plasticity * Rotordynamics * Solid mechanics * Soil mechanics * Stress waves * [...]No related posts.]]>

* Acoustics

* Analytical mechanics

* Computational mechanics

* Contact mechanics

* Continuum mechanics

* Dynamics

* Elasticity

* Experimental mechanics

* Fatigue

* Finite element method

* Fluid mechanics

* Fracture mechanics

* Mechanics of materials

* Mechanics of structures

* Plasticity

* Rotordynamics

* Solid mechanics

* Soil mechanics

* Stress waves

* Viscoelasticity

Adapted from the Wikipedia article Applied mechanics, under the G. N. U. Free Documentation License. Please also see http://en.wikipedia.org/wiki

Mechanics

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]]> http://www.contour2002.org/article/applied-mechanics-major-topics-of-applied-mechanics/feed 0 Waveguide (acoustics) – Exampleshttp://www.contour2002.org/article/waveguide-acoustics-examples http://www.contour2002.org/article/waveguide-acoustics-examples#comments Sat, 25 Jun 2011 14:52:37 +0000 http://www.contour2002.org/article/waveguide-acoustics-examples AcousticsOne example might be a speaking tube used aboard ships for communication between decks. Other examples include the rear passage in a transmission line loudspeaker enclosure, the ear canal or a device like a stethoscope. The term also applies to guided waves in solids. A duct for sound propagation also behaves like a transmission line [...]No related posts.]]>

One example might be a speaking tube used aboard ships for communication between decks.

Other examples include the rear passage in a transmission line loudspeaker enclosure, the ear canal or a device like a stethoscope. The term also applies to guided waves in solids.

A duct for sound propagation also behaves like a transmission line (e.g. air conditioning duct, car muffler, etc.). The duct contains some medium, such as air, that supports sound propagation. Its length is typically around quarter of the wavelength which is intended to be guided, but the dimensions of its cross section are smaller than this. Sound is introduced at one end of the tube by forcing the pressure to vary in the direction of propagation, which causes a pressure gradient to travel perpendicular to the cross section at the speed of sound. When the wave reaches the end of the transmission line, its behaviour depends on what is present at the end of the line. There are three generalized scenarios:

A low impedance load (e.g. leaving the end open in free air) will cause a reflected wave in which the sign of the pressure variation reverses, but the direction of the pressure wave remains the same.

A load that matches the characteristic impedance (defined below) will completely absorb the wave and the energy associated with it. No reflection will occur.

A high impedance load (e.g. by plugging the end of the line) will cause a reflected wave in which the direction of the pressure wave is reversed but the sign of the pressure remains the same.

Since a transmission line behaves like a four

Acoustics
terminal model, one cannot really define or measure the impedance of a transmission line component. One can however measure its input or output impedance. It depends on the cross-sectional area and length of the line, the sound frequency, as well as the characteristic impedance of the sound propagating medium within the duct. Only in the exceptional case of a closed end tube (to be compared with electrical short circuit), the input impedance could be regarded as a component impedance.

Where a transmission line of finite length is mismatched at both ends, there is the potential for a wave to bounce back and forth many times until it is absorbed. This phenomenon is a kind of resonance and will tend to attenuate any signal fed into the line.

When this resonance effect is combined with some sort of active feedback mechanism and power input, it is possible to set up an oscillation which can be used to generate periodic acoustic signals such as musical notes (e.g. in an organ pipe).

The application of transmission line theory is however seldom used in acoustics. An equivalent four terminal model which splits the downstream and upstream waves is used. This eases the introduction of physically measurable acoustic characteristics, reflection coefficients, material constants of insulation material, the influence of air velocity on wavelength (Mach number), etc. This approach also circumvents impractical theoretical concepts, such as acoustic impedance of a tube, which is not measurable because of its inherent interaction with the sound source and the load of the acoustic component.

Category:Acoustics

ru:Акустический волновод
Adapted from the Wikipedia article Waveguide (acoustics), under the G. N. U. Free Documentation License. Please also see http://en.wikipedia.org/wiki

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]]> http://www.contour2002.org/article/waveguide-acoustics-examples/feed 0 Fisheries acoustics – Introductionhttp://www.contour2002.org/article/fisheries-acoustics-introduction http://www.contour2002.org/article/fisheries-acoustics-introduction#comments Sat, 25 Jun 2011 14:51:23 +0000 http://www.contour2002.org/article/fisheries-acoustics-introduction AcousticsFisheries acoustics includes a range of research and practical application topics using acoustical devices as sensors in aquatic environments. Acoustical techniques can be applied to sensing aquatic animals, zooplankton, and physical and biological habitat characteristics. Adapted from the Wikipedia article Fisheries acoustics, under the G. N. U. Free Documentation License. Please also see http://en.wikipedia.org/wiki No [...]No related posts.]]>

Fisheries acoustics includes a range of research and practical application topics using acoustical devices as sensors in aquatic environments. Acoustical techniques can be applied to sensing aquatic animals, zooplankton, and physical and biological habitat characteristics.

Adapted from the Wikipedia article Fisheries acoustics, under the G. N. U. Free Documentation License. Please also see http://en.wikipedia.org/wiki

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