沉闷的夏天有时的确让人透不过气来，最近的我比较喜欢呆在家里，做件小蛋糕，打杯鲜果汁，往里面放几颗冷冻冰块，再配上一本书，就这样过上一个简单的周末，悠然涣散，怡然自得。如果你偶尔也会像笔者那样，那么今天推荐的这款多功能手持搅拌器就最适合不过了，它的组件非常简单，轻便小巧，做果汁、制果酱、调奶昔、打奶油、做土豆泥沙拉……一切都来得轻而易举。【SGK1238多功能手持搅拌器：产品信息】一、产品信息产品名称：SGK1238多功能手持搅拌器生产企业：佛山艾诗凯奇电气有限公司产品参数：二、产品特殊卖点（1）外形小巧时尚，容易收纳。（2）450W大功率纯铜电机，动力强劲，噪音小。（3）两个档位电动开关，多档速度调节，更容易掌控。（4）多功能创作，满足不同需求的你：做果汁、制果酱、调奶昔、打奶油、做土豆泥沙拉……【SGK1238多功能手持搅拌器：产品外观评测】小巧百搭外观&健康安全用料　　这款多功能手持搅拌器看起来特别有小资的感觉，就连包装也是非常别致，除了内外两个五层瓦楞硬纸皮包装箱，里面还有一个纸浆模塑固定，每个组件都用独立的透明塑料袋包装，如此妥善保护你刚入手的心头好，想必会首先为你带来一个愉悦的开箱体验。　　搅拌器的外观采用了百搭的黑色作为主色调，可以轻松融入各种居室设计当中，优雅的黑色还不忘与普通的搅拌器拉开档次，这样高逼格也自然而然上来了。在轻描淡写的红色搭配下，又多一份的活力，让你的厨房充满灵感与创意。　　除了主机，产品配送的一些组件还是非常贴心的：500ml的透明量杯刚好够一个人的分量，适合崇尚小资生活的你；小巧的置物架可以安装在墙上，把组件悬挂起来，巧妙地节省空间。　　整套搅拌器全部采用食品级304不锈钢及食品级ABS塑料做成，材质对人体无毒无害，健康环保，经久耐用。人性化主机设计　　非常喜欢它的主机，仿人体工学设计的圆润流线型机身，拿起来手感特别好，舒适稳固，而且它的重量轻盈，长时间手持也不会觉得累。主机顶部有一个齿轮型的调速开关，从左到右，速度由慢到快调节。拿在手里，拇指刚好能触碰到的位置有两档点动开关，按下后机子就能直接开动，Ⅰ档是慢速，Ⅱ档是高速，使用搅拌或者打蛋功能时，最好选用Ⅰ档，使用切碎功能时适合使用Ⅱ档。　　机身末端与各种器皿相接的位置有个旋转锁扣，扣紧或松开时上面的三角形符号与各个搅拌器上的开关锁图标对准，组装起来简单快捷，结实稳固。整个机身设计都相当人性化。灵活搭配&烹饪好助手　　这款多功能料理器共有3种&装备&，它可以是一个搅拌器，也可以是一个打蛋器，你需要的时候，它还可以是一个切碎器，丰富多样的功能用起来灵活方便，起码在家中能想到要做的料理，它都能用得上，例如做果汁、奶昔、做蛋糕、制作肉馅、做汤羹等，是个不可或缺的厨房利器。　　组装后的利器长度刚刚好，使用时比较顺手，不会碍事，也不会用得很累。　　接下来看看三种刀片的细节，搅拌器的两块刀片末端分别指向不同的方向，搅拌更加均匀彻底，锋利的刀片在高速工作状态下，全方位切割食材。刀片的周围还设有一个防溅护罩，可以有效防止食材在高速旋转下到处乱溅。　　打蛋器上的不锈钢线排列错中有序，弹性好，不易变形，在450W的强大功率下，快速轻松打出松软滑腻的奶油来。　　切碎器特别适合用来绞肉、碎胡萝卜、洋葱、做蒜末、切草药等，它的刀片采用了S型设计，大大增加了食材与刀片的接触面积，把食材进行全方位切割、打碎，出品更加精碎、细腻。&【SGK1238多功能手持搅拌器：产品性能评测】　　耳听为虚，眼见为实，外观说多了，接下来还是为大家展示一下试用结果更加实际。笔者向来对水果奶昔从不抗拒，夏日炎炎，果断选择了鲜嫩多汁、美容养颜的圣女果来做这次晒单&前菜&。搅拌功能　　做奶昔需要使用的是搅拌功能，一般来说，用配送的杯子做单人分量的冷饮刚刚好。首先要把洗干净的圣女果放进杯里，再倒上牛奶，牛奶的分量因个人喜好而定。组装好搅拌器，按下Ⅰ档就可以开始制作了，这时圣女果被快速搅烂，牛奶与水果充分融合，汁液表面在搅拌过程中能保持相对平稳，不会溢出桌面。一分钟不够就能打出一杯新鲜美味的奶昔，香甜滑嫩，非常容易入口，如果加上一点沙冰，口感更好，特别适合夏天饮用。&打蛋功能　　打蛋器对于制作西点来说必不可少，用它来打蛋白糊，做出的蛋糕特别柔软。但是由于今天笔者没有准备做奶油的食材，就直接选用了厨房里最常用的鸡蛋来做蛋液展示。首先在杯内打入三个鸡蛋，然后直接启动打蛋器搅拌，毫不费力之下，蛋清与蛋液被快速打散，融合成蛋液，用来做蒸水蛋或者做黄金炒饭都相当赞。&切碎功能　　除了果汁、奶昔，夏天没有胃口的时候，相信不少人会尝试做沙拉代替晚饭，土豆泥沙拉绝对是一个不二选择，香滑软糯，营养丰富，内含的淀粉质能快速充饥，还是瘦身的最佳营养餐。　　用清水煮熟后的土豆非常松软，表皮很容易脱落，只要用手轻轻剥开就可以了。因为切碎器皿上有MAX最大容量位线，土豆需要切成小块后放进去，安装好切碎器后，点按Ⅱ档后开始制作，土豆在刀片高速切割下被瞬间打成泥状。从透明切碎杯外看到打得差不多时，可以打开上盖，此时土豆泥清新的香味逼人，均匀细腻，简单加点调味料，再在上面撒点火腿末就完成了美味的土豆泥沙拉了！&　　为了让它的功能更具说服力，下面我也做绞肉跟切胡萝卜粒的尝试，让大家看一下它的表现如何。切碎前，必须把食材都切成小块，然后放进切碎杯里。大概二十秒以内的时间，食材就能全部被彻底切碎，绞出的肉末均匀细滑，煮熟后也适合家中宝宝食用，而经过切细的胡萝卜则全都变成碎小颗粒状，非常适合做馅料。　　当然，你还可以把肉跟胡萝卜一同放进去，也能轻松做出新鲜的胡萝卜肉馅来，不用人手切割，自动搅匀。其实，只要加点创意，还能做出意想不到的料理来。&&【SGK1238多功能手持搅拌器：产品清洁简易性评测】　　清洗通常都是我们比较头痛的问题，但当你尝试了这套搅拌器的清洗后，将会不能自拔地爱上它，因为它仅需10多秒的时间就能自动清洗干净，实在太简便了！我们只需要在容器内装上清水，然后启动快速搅拌模式，在刀片高速旋转下，容器内的水形成强大的&刷洗&动力，全程无需人手操作，不会伤手。洗完后把水倒掉，把各部分晾干就可以了，步骤非常简单，完全不必担心清洗的问题！&【SGK1238多功能手持搅拌器：产品评测总结】产品外观：在厨卫方面一直以榨汁机、原汁机为主打的SKG最近推出的这一以轻便为特色的手持搅拌器系列（两款）并没有敷衍观众，从细节到整个外观都可以看出商家在新品上的用心。1238这款时尚小巧的多功能料理机外观十分讨好，为简单的生活带来了更多的灵感，体现了SKG着力打造的时尚、创意、健康的品牌理念。产品性能：除了外观，性能上也是无可挑剔的，无论是调奶昔、打蛋液、绞肉还是做土豆泥沙拉，它都能把成品完美地呈现在你眼前，除了笔者以上所做的尝试，它还能实现更多的功能，只要你加点创意，绝对能满足不同需求的你。更重要的是，它450W的大功率强动力，带来了出色的烹饪效率。就因为它做得快，那么，平时&忙碌&的我们，才有更多的时间去体验慢生活。使用体验：虽然是手持的搅拌器，但是使用起来毫不费力，而且非常好用，主机上的调速旋钮以及两个档位的电动开关，让整体的使用更具可操作性，可以有针对性地烹饪各种食材。开关点按即动，松手即停，也让它同时具有了较高的安全性。搅拌器的快速自动清洗功能也让整个使用过程有了让人满意的结尾，这都无不体现着人性化的生活态度。产品性价比：产品在包装与本身用料上都做得相当认真，整套搅拌器均以食品级304不锈钢、食品级ABS塑料做成，保证了食用的安全性，器材使用寿命更长，对于一款多功能、耐用的产品来说，性价比相信不言而喻。
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Search the FAQ Archives
Acoustics FAQ
See reader questions & answers on this topic! -
Archive-name: physics-faq/acoustics
Last-modified: 7th September 1997
Version: 0.09
*** ACOUSTICS FAQ ***
DISCLAIMER - NO WARRANTY OF ANY KIND WHATSOEVER IS MADE FOR THE FITNESS
OF THE CONTENTS OF THIS FAQ.
In order to allow maximum compatibility only ASCII symbols are used
* To make acoustics accessible to a wider public
* To encourage cooperation within the acoustics community
Changes since previous version
==============================
Web site revision & additions
software revisions
added and qs following renumbered
2.10 revised
2.11 revised
musical intervals added, following renumbered (inc ref 6.10)
address & e-mail additions and revisions
1] Resource Pointers
What acoustics related news groups and FAQs are there ?
What World Wide Web sites are there ?
What acoustics software is available on the Net ?
What acoustics books and journals are there ?
2] Basic Acoustics
What is sound ?
What is a decibel (dB) ?
How is sound measured ?
What does dB(A) or "A-weighted" mean ?
How do sound levels add ?
How does the ear work ?
At what level does sound become unsafe ?
What is sound intensity ?
How does sound decay with distance ?
What is the sound power level ?
What is the speed of sound in air, water .. ?
What is meant by loudness?
3] Vibration
What is vibration?
How is vibration measured ?
How is vibration isolated and controlled ?
4] Architectural & Building Acoustics
What is reverberation time ?
What is the sound absorption coefficient ?
What is the difference between insulation & absorption ?
How is sound insulation measured ?
How do I improve the noise insulation of my house/dwelling ?
5] Reserved
6] Miscellaneous Questions
What is active noise control ?
What causes a sonic boom ?
Can you focus sound ?
What is sonoluminescence ?
Why does blowing over a bottle make a note ?
What is pitch ?
What are musical intervals?
What causes "helium voice" ?
What is structural acoustics ?
6.10 What is the Doppler effect ?
6.11 What is white noise, pink noise ?
8] Various Tables
Formula for A weighting
9] List of National Acoustic Societies
-------------------------------------------------------------
-------------------------------------------------------------
Resource Pointers
-----------------
What acoustic related news groups and FAQs are there ?
news groups
-----------
news:alt.sci.physics.acoustics - started by Angelo Campanella - now the
principal group for discussion of acoustics topics. Ang's CV is at URL
news:sci.physics - general physics but occasionally acoustics related
questions are posted.
news:rec.audio.tech - includes discussion on audio equipment, speakers
etc. There are other
groups which may be of interest.
news:alt.support.hearing-loss and
for sufferers of these complaints
news:bionet.audiology - matters relating to hearing and hearing loss
news:bit.listserv.deaf-l
- usenet seems an ideal communication medium.
news:comp.dsp - the group for people interested in computing digital
signal processing solutions, FFTs FIRs IIRs etc.
news:comp.speech - speech recognition and simulation
news:comp.sys.ibm.pc.soundcard.misc - various discussion of use of
internal soundcards in IBM compatible computers.
The main archive site for all usenet FAQs is
ftp://rtfm.mit.edu/pub/usenet/
A list of sites (including html) for the Acoustics FAQ is at
/~consult/Acoustics_FAQ_mirrors.html
--------------
The Active Noise Control FAQ by Chris Ruckman is at
--------------
The Tinnitus FAQ deals with a range of hearing disorders. It is
maintained by Mark Bixby and available at
http://www.cccd.edu/faq/tinnitus.html
--------------
The Audio FAQ, with everything you ever wanted to know about the
subject, from preamplifiers to speakers and listening room acoustics.
It is located in the pub/usenet/rec.audio.* directories
--------------
faq maintained by Andrew Hunt has information on speech
processing and some software links
http://www.speech.su.oz.au/comp.speech/
--------------
What World Wide Web sites are there ?
Many acoustical web resources can be found from links in the first two
locations or the "search engines" listed below.
(virtual lib for acoustics & vibration with useful links)
http://capella.dur.ac.uk/doug/acoustics.html
(wide selection of acoustics related links)
http://www./CampusWorld/pub/ScienceNet/first.html
(science questions and answers)
(simple acoustics introduction from David Worrall)
http://www.mme.tcd.ie/~m.carley/Notes/
(theoretical basic aco difficult stuff like
the wave equation etc, in hypertext for browsing, or gzipped
Postscript format for downloading)
(Acoustical Society of America home page with several links and
comprehensive career section, book lists and Society info etc)
(Angelo Farina has published a variety of papers - some are
available in zipped MSWord format)
http://eaa.essex.ac.uk/eaa/
(European Acoustics Association)
(Institute of Noise Control Engineering home page)
http://super-highway.net/~wattsup/Audio%20related%20Site%20list.html
(Steve Ekblad's extensive audio related BBS and Internet list)
(Technical societies, conferences etc etc but not specifically
acoustics related)
(main ISO standards page)
(national standards organizations addresses)
(official ANSI site)
The Digital Equipment Corporation has an extremely powerful Advanced
Search facility at:
alternatively try searches on:
(can also be used as Usenet posting gateway)
or use your nearest Archie site to look for files you want.
What acoustics software is available on the Net ?
A range of programs available for downloading from the Simtel archive.
Spectrogram 3.2 - Accurate realtime Win95 spectrum analysis program
(freeware) by Richard Horne is at a few sites including:
/info/pc/win95/sounds/gram32.zip
faq has several links to speech related software
including speech recognition and text to speech programs.
There are a few programs for various platforms listed at URL
The programs listed are mainly for sound analysis and editing.
Some software is available for audio systems design at URL
Odeon is a program for architectural acoustics. A demonstration version
is available by ftp. The demo includes a large database for
coefficients of absorption. A web page at URL
describes the capabilities of the program and gives the ftp address.
Also some interactive acoustics software (eg room acoustics, RT,
decibel conversion etc) is available at a couple of sites.
What acoustics books and journals are there ?
There is a large range of books available on the subject. Generally the
choice of book will depend on which approach and subject area is of
interest. A few books are listed below:
&&Introduction to Sound
&&Speaks, C
Good foundation for acoustics principles
&&Acoustics Source Book
&&Parker, S (editor)
Basic introductory articles on many topics discussed in the
group. Old book - technology a bit dated.
&&The Science of Sound
&&Rossing, T
Introductory book on acoustics, music and audio
&&Fundamentals of Acoustics
&&Kinsler, L
Good overall coverage of acoustics but includes lots of theory
&&Acoustics ...
&&Pierce, A
Classic advanced text - lots of theory
&&Engineering Noise Control
&&Bies, D & Hansen, C
Practically biased with examples. Partially updated and corrected.
&&Handbook of Acoustical Measurements and Noise Control
&&Harris C
Comprehensive practical reference book.
A list of recently reviewed noise-related books is at URL
/inceusa/books.html
Some Journals
-------------
Journal of the Acoustical Society of America (monthly)
Noise Control Engineering (US - every 2 months)
Acoustics Bulletin (UK - every 2 months)
Acta Acustica (P.R.China)
Acta Acustica / Acustica (Europe - 6 per year)
Journal of the Acoustical Society of Japan (E) (English edn - 2 months)
Acoustics Australia (3 per year)
Journal of Sound & Vibration (UK - weekly)
Journal of the Audio Engineering Society (US - 10 per year)
Applied Acoustics (UK - 12 per year)
---------------------------------------------------------------
---------------------------------------------------------------
Definitions used:
10^(-5) indicates 10 raised to the power of minus 5
1.0E-12 indicates 1.0 x 10^(-12)
1 pW indicates 1 picowatt i.e. 1.0E-12 Watt
W/m^2 indicates Watts per square metre
lg indicates logarithm to base 10
sqrt indicates the square root of
pi = 3.142
Lw is sound power level, the w is subscripted
Basic Acoustics
---------------
What is sound ?
Sound is the quickly varying pressure wave within a medium.
We usually mean audible sound, which is the sensation (as detected by
the ear) of very small rapid changes in the air pressure above and
below a static value. This "static" value is atmospheric pressure
(about 100,000 Pascals) which does nevertheless vary slowly, as shown
on a barometer. Associated with the sound pressure wave is a flow of
energy. Sound is often represented diagrammatically as a sine wave, but
physically sound (in air) is a longitudinal wave where the wave motion
is in the direction of the movement of energy. The wave crests can be
considered as the pressure maxima whilst the troughs represent the
pressure minima.
How small and rapid are the changes of air pressure which cause sound?
When the rapid variations in pressure occur between about 20 and 20,000
times per second (ie at a frequency between 20Hz and 20kHz) sound is
potentially audible even though the pressure variation can sometimes
be as low as only a few millionths of a Pascal. Movements of the ear
drum as small as the diameter of a hydrogen atom can be audible! Louder
sounds are caused by greater variation in pressure - 1 Pascal, for
example, will sound quite loud, provided that most of the acoustic
energy is in the mid-frequencies (1kHz - 4kHz) where the ear is most
sensitive.
What makes sound?
Sound is produced when the air is disturbed in some way, for example
by a vibrating object. A speaker cone from a hi-fi system serves as a
good illustration. It may be possible to see the movement of a bass
speaker cone, providing it is producing very low frequency sound. As
the cone moves forward the air immediately in front is compressed
causing a slight increase in air pressure, it then moves back past its
rest position and causes a reduction in the air pressure (rarefaction).
The process continues so that a wave of alternating high and low
pressure is radiated away from the speaker cone at the speed of sound.
What is a decibel (dB) ?
The decibel is a logarithmic unit which is used in a number of
scientific disciplines. In all cases it is used to compare some
quantity with some reference value. Usually the reference value is the
smallest likely value of the quantity. Sometimes it can be an
approximate average value.
In acoustics the decibel is most often used to compare sound pressure,
in air, with a reference pressure. References for sound intensity,
sound power and sound pressure in water are amongst others which are
also commonly in use.
Reference sound pressure (in air) = 0.00002 = 2E-5 Pa (rms)
= 0. = 1E-12 W/m^2
= 0. = 1E-12 W
pressure (water)
= 0.000001 = 1E-6 Pa
Acousticians use the dB scale for the following reasons:
1) Quantities of interest often exhibit such huge ranges of
variation that a dB scale is more convenient than a linear
For example, sound pressure radiated by a submarine may
vary by eight orders of magnitude depending on direction.
2) The human ear interprets loudness on a scale much closer to
a logarithmic scale than a linear scale.
How is sound measured ?
A sound level meter is the principal instrument for general noise
measurement. The indication on a sound level meter (aside from
weighting considerations) indicates the sound pressure, p, as a level
referenced to 0.00002 Pa.
Sound Pressure Level = 20 x lg (p/0.00002) dB
Peak levels are occasionally quoted. During any given time interval
peak levels will be numerically greater, and often much greater than
the (rms) sound pressure level.
What does dB(A) or "A-weighted" mean ?
Noise was not of particular concern at the beginning of the century.
The first electrical sound meter was reported by George W Pierce in
Proceedings of the American Academy of Arts and Sciences, v 43 (1907-8)
A couple of decades later the switch from horse-drawn vehicles to
automobiles in cities led to large changes in the background noise
climate. The advent of "talkies" -
film sound - was a big stimulus to
sound meter patents of the time, but there was still no standard method
of sound measurement.
The first tentative standard for sound level meters (Z24.3) was
published by the American Standards Association in 1936, sponsored by
the Acoustical Society of America. The tentative standard shows two
frequency weighting curves "A" and "B" which were modelled on the ear's
response to low and high levels of sound respectively.
The most common weighting today is "A-weighting" dB(A), which is very
similar to that originally defined as Curve "A" in the 1936 standard.
"C-weighting" dB(C), which is used occasionally, has a relatively flat
response. "U-weighting" is a recent weighting which is used for
measuring audible sound in the presence of ultrasound, and can be
combined with A-weighting to give AU-weighting. The A-weighting formula
is given in section 8 of the FAQ.
In addition to frequency weighting, sound pressure can be weighted in
time with fast, slow or impulse response. Measurements of sound
pressure level with A-weighting and fast response are also known as the
"sound level".
Some sound level meters can measure the average sound level of a noise
over a given time. It is called the equivalent continuous sound level
(L sub eq) and is A-weighted but not time weighted.
How do sound levels add ?
If there are two sound sources in a room - for example a radio
producing an average sound level of 62.0 dB, and a television producing
a sound level of 73.0 dB - then the total sound level is a logarithmic
Combined sound level = 10 x lg ( 10^(62/10) + 10^(73/10) )
Note: for two different sounds, the combined level cannot be more than
3 dB above the higher of the two sound levels. However, if the sounds
are phase related there can be up to a 6dB increase in SPL.
How does the ear work ?
The eardrum is connected by three small jointed bones in the air-filled
middle ear to the oval window of the inner ear or cochlea, a fluid-
filled spiral coil about one and a half inches in length. Over 10,000
hair cells on the basilar membrane along the cochlea convert minuscule
movements to nerve impulses, which are transmitted by the auditory
nerve to the hearing center of the brain.
The basilar membrane is wider at its apex than at its base, near the
oval window, whereas the cochlea tapers towards its apex. Different
groups of the delicate hair sensors on the membrane, which varies in
stiffness along its length, respond to different frequencies
transmitted down the coil. The hair sensors are one of the few cell
types in the body which do not regenerate. They may therefore become
irreparably damaged by large noise doses. Refer to the Tinnitus FAQ for
more information on hearing disorders.
ftp://rtfm.mit.edu/pub/usenet/news.answers/medicine/
At what level does sound become unsafe ?
It is best, where possible, to avoid any unprotected exposure
to sound pressure levels above 100dB(A). Use hearing protection when
exposed to levels above 85dB(A), especially if prolonged exposure is
Damage to hearing from loud noise is cumulative and is
irreversible. Exposure to high noise levels is also one of the main
causes of tinnitus. The safety aspects of ultrasound scans are the
subject of ongoing investigation.
There are other health hazards from extended exposure to vibration. An
example is "white finger", which is found amongst workers who use hand-
held machinery such as chain saws.
What is sound intensity ?
This may be defined as the rate of sound energy transmitted in a
specified direction per unit area normal to the direction. With good
hearing the range is from about 0. Watt per square metre
to about 1 Watt per square metre (12 orders of magnitude greater). The
sound intensity level is found from intensity I (W/m^2) by:
Sound Intensity Level = 10 x lg (I/1.0E-12) dB
Note: 1.0E-12 W/m^2 normally corresponds to a sound pressure of about
2.0E-5 Pascals which is used as the datum acoustic pressure in air.
Sound intensity meters are becoming increasingly popular for
determining the quantity and location of sound energy emission.
How does sound decay with distance ?
The way sound changes with distance from the source is dependent on the
size and shape of the source and also the surrounding environment and
prevailing air currents. It is relatively simple to calculate provided
the source is small and outdoors, but indoor calculations (in a
reverberant field) are rather more complex.
If the noise source is outdoors and its dimensions are small compared
with the distance to the monitoring position (ideally a point source),
then as the sound energy is radiated it will spread over an area which
is proportional to the square of the distance. This is an 'inverse
square law' where the sound level will decline by 6dB for each doubling
of distance.
Line noise sources such as a long line of moving traffic will radiate
noise in cylindrical pattern, so that the area covered by the sound
energy spread is directly proportional to the distance and the sound
will decline by 3dB per doubling of distance.
Close to a source (the near field) the change in SPL will not follow
the above laws because the spread of energy is less, and smaller
changes of sound level with distance should be expected.
In addition it is always necessary to take into account attenuation due
to the absorption of sound by the air, which may be substantial at
higher frequencies. For ultrasound, air absorption may well be the
dominant factor in the reduction.
What is the sound power level ?
Sound power level, Lw, is often quoted on machinery to indicate
the total sound energy radiated per second. The reference power is
taken as 1pW.
For example, a lawn mower with sound power level 88dB(A) will produce
a sound level of about 60dB(A) at a distance of 10 metres. If the sound
power level was 78dB(A) then the lawn mower sound level would be only
50dB(A) at the same distance.
What is the speed of sound in air, water .. ?
The speed of sound in air at a temperature of 0 degC and 50% relative
humidity is 331.6 m/s. The speed is proportional to the square root of
absolute temperature and it is therefore about 12 m/s greater at 20
degC. The speed is nearly independent of frequency and atmospheric
pressure but the resultant sound velocity may be substantially altered
by wind velocity.
A good approximation for the speed of sound in other gases at standard
temperature and pressure can be obtained from
c = sqrt (gamma x P / rho)
where gamma is the ratio of specific heats, P is 1.013E5 Pa and rho is
the density.
The speed of sound in water is approximately 1500 m/s. It is possible
to measure changes in ocean temperature by observing the resultant
change in speed of sound over long distances. The speed of sound in an
ocean is approximately:
c = 1449.2 + 4.6T - 0.055T^2 + 0.00029T^3 + (1.34-0.01T)(S-35) + 0.016z
T temp in degrees Celsius, S salinity in parts per thousand
z is depth in meters
See also CRC Handbook of Chemistry & Physics for some other substances
and Dushaw & Worcester JASA (1993) 93, pp255-275 for sea water.
What is meant by loudness?
Loudness is the human impression of the strength of a sound. The
loudness of a noise does not necessarily correlate with its sound
level. Loudness level of any sound, in phons, is the decibel level of
an equally loud 1kHz tone, heard binaurally by an otologically normal
listener. Historically, it was with a little reluctance that a simple
frequency weighting "sound level meter" was accepted as giving a
satisfactory approximation to loudness. The ear senses noise on a
different basis than simple energy summation, and this can lead to
discrepancy between the loudness of certain repetitive sounds and their
sound level.
A 10dB sound level increase is considered to be about twice as loud in
many cases. The sone is a unit of comparative loudness with 0.5 sone=30
phons, 1 sone=40 phons, 2 sones=50 phons, 4 sones = 60 phons etc. The
sone is inappropriate at very low and high sound levels where
subjective perception does not follow the 10dB rule.
Loudness level calculations take account of "masking" - the process by
which the audibility of one sound is reduced due to the presence of
another at a close frequency. The redundancy principles of masking are
applied in digital audio broadcasting (DAB), leading to a considerable
saving in bandwidth with no perceptible loss in quality.
-------------------------------------------------------------
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What is vibration ?
When something oscillates about a static position it can be said to
vibrate. The vibration of a speaker diaphragm produces sound, but
usually vibration is undesirable. Common examples of unwanted vibration
are the movement of a building near a railway line when a train passes,
or the vibration of the floor caused by a washing machine or spin
dryer. Floor vibration can be reduced with however
there is often a penalty to pay in the form of a slight increase in the
machinery vibration and its consequent deterioration.
How is vibration measured ?
Vibration is monitored with an accelerometer. This is a device that is
securely attached by some means to the surface under investigation. The
accelerometer produces a tiny electrical charge output, proportional
to the surface acceleration, which is then amplified by a charge
amplifier and recorded or observed with a meter. The frequencies of
interest are generally lower than sound, and range from below 1 Hz to
about 1 kHz.
It is sometimes more useful to know the velocity or displacement rather
than the acceleration. In the case of velocity, it is necessary to
integrate the acceleration signal. A second integration will provide
a displacement output. If the vibration is sinusoidal at a known
frequency, f, then an integration is easily calculated by dividing the
original by 2 x pi x f (noting that there is a phase change)
Example: A machine is vibrating sinusoidally at 79.6 Hz with an rms
acceleration of 10 m/s^2.
Its rms velocity is therefore 10/(2 x pi x 79.6) = 20 mm/s
Its rms displacement is
10/(4 x pi^2 x 79.6^2) = 0.04 mm
How is vibration isolated and controlled ?
Vibration problems are solved by considering the system as a number of
springs and masses with damping. It is sometimes possible to reduce the
problem to a single mass supported by a spring and a damper.
If the vibration is produced by a motor inside a machine, it is usually
desirable to ensure that the frequency of motor oscillations (the
forcing frequency) is well above the frequency of the natural resonance
of the machine on its support. This is achieved by altering the mass
or stiffness of the system as appropriate.
The method of vibration isolation is very easy to demonstrate with a
weight held from a rubber band. As the band is moved up and down very
slowly the suspended weight will move by the same amount. At resonance
the weight will move much more, but as the frequency is increased still
further the weight will become almost stationary. In practical
circumstances springs are more likely to be used in compression than
tension, but the principles are exactly the same.
A further method of vibration control is to attempt to cancel the
forces involved using a Dynamic Vibration Absorber. Here an additional
"tuned" mass-spring combination is added so that it exerts a force
equal and opposite to the unwanted vibration. They are only appropriate
when the vibration is of a fixed frequency.
Active vibration control, using techniques akin to active noise
control, is now coming into use.
Important:-
Intuitive attempts to reduce vibration from machinery can sometimes
instead aggravate the problem. This is especially true when care was
originally taken to minimize vibration at the time of design,
manufacture and installation.
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Architectural & Building Acoustics
----------------------------------
What is reverberation time ?
Work on room acoustics was pioneered by Wallace Clement Sabine 1868-
1919 (see his Collected Papers on Acoustics, 1922).
The reverberation time, T, is defined as the time taken for sound
energy to decay in a room by a factor of one million (ie by 60 dB). It
is dependent on the room volume and its total absorption.
In metric units
0.161 x room Volume
----------------------------------------------
sum of Surface areas x absorption coefficients
What is the sound absorption coefficient ?
The absorption coefficient of a material is ideally the fraction of the
randomly incident sound power which is absorbed, or otherwise not
reflected. It can be determined in two main ways, and there are often
variations in the results depending upon the method of measurement
chosen. It is standard practice to measure the coefficient at the
preferred octave frequencies over the range of at least 125Hz - 4kHz.
For the purposes of architectural design, the Sabine coefficient
(calculated from reverberation chamber measurements) is preferred.
Interestingly some absorbent materials are found to have a Sabine
coefficient in excess of unity at higher frequencies. This is due to
edge effects and when this occurs the value can be taken as 1.0
The Odeon computer program includes a file of absorption coefficients.
What is the difference between insulation & absorption ?
There is often confusion between sound insulation and sound absorption.
Sound insulation is required in order to eliminate the sound path from
a source to a receiver such as between apartments in a building, or to
reduce unwanted external noise inside a concert hall. Heavy materials
like concrete tend to be the best materials for sound insulation -
doubling the mass per unit area of a wall will improve its insulation
by about 6dB. It is possible to achieve good insulation with much less
mass by instead using a double leaf partition (two separated
independent walls).
Sound absorption occurs when some or all of the incident sound energy
is either converted into heat or passes through the absorber. For this
reason good sound absorbers do not of themselves make good sound
insulators. Although insulation and absorption are different concepts,
there are many instances where the use of sound absorbers will improve
insulation. However absorption should not be the primary means of
achieving good sound insulation.
How is sound insulation measured ?
The measurement method depends on the particular situation. There are
standards for the measurement of the insulation of materials in the
laboratory, and for a number of different field circumstances. Usually
the procedures involve generating a loud sound of a specified type and
monitoring the transmitted noise.
It is very useful to have a single number to characterize the
insulation of a partition. Measurements are often conducted in third-
octaves, and the reduction plotted on a graph. A reference curve is
then fitted to the measurements using a specified procedure, and the
value of this curve at 500 Hz is taken as the figure. There is a slight
difference in procedure between the U.S. and ISO standards, but the
methods are basically similar. The same is also true for impact noise
transmission assessment, where a standard tapping machine is in use to
hammer floors. Sound pressure levels in the room below are monitored.
How do I improve the noise insulation of my house/dwelling?
This is one of the most commonly asked questions of noise consultants.
Firstly you should consider whether better insulation is really
essential. The method of noise insulation will depend on the exact
situation, so the advice of a competent person should be sought at an
early stage. Sound insulation is most often asked for in order to keep
out unwanted noise, but is occasionally requested for the purpose of
minimizing disturbance to others. The following ideas may serve as
guidelines.
When the noise is from an external source such as a main road it may
be possible, if planning authorities permit, to screen with a noise
barrier. These can be effective providing that the direct line of sight
between traffic and house is concealed by the barrier.
The weak point for sound transmission to and from a building is most
often via the windows. Double glazing will usually afford noticeably
better protection than single glazing, but in areas of high external
noise it might be preferable to have double windows with a large air
gap and acoustic absorbent material in the reveals. A drawback of
improving external insulation is that, for some people, the resultant
lower background level can
it can also make noise
transmission through party walls more apparent. The fitting of new
windows may reduce the level of air ventilation, and it will be vital
to compensate for this, if necessary with a noise attenuating system.
You may also need to consider noise penetration through the roof,
floors, ceilings and walls.
Noise through party walls can be reduced by the addition of a false
wall. This is constructed from a layer of sound insulating material,
commonly plasterboard, separated from the party wall by a large void
containing acoustic quilting. The false wall must not be connected to
the party wall because that would allow sound transmission paths. The
quality of construction is an important consideration if optimal levels
of attenuation are desired. It is advisable to contact an independent
noise consultant before allowing any building works to commence.
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Miscellaneous Questions
----------------------
What is active noise control ?
ANC is an electronic method of reducing or removing unwanted sound by
the production of a pressure wave of equal amplitude but opposite sign
to the unwanted sound. When the electronically produced inverse wave
is added to original unwanted sound the result is sound cancellation.
This method of noise control is becoming increasingly popular for a
variety of uses. It is sometimes considered a miracle "cure-all" for
noise problems which, at the present time, is not the case. For example
noise cancellation in 3D spaces, such as living areas, is very
difficult to achieve. However it can be more successful locally, eg for
a passenger sitting in an aircraft or car. There are many institutions
and companies around the world working on the technology to increase
the circumstances where ANC can be used effectively. The award winning
Active Noise Control FAQ is maintained by Chris Ruckman and available
at a number of sites worldwide including:
What causes a sonic boom ?
(from "Aircraft Noise" by Michael T Smith, Cambridge, 1989)
When the speed of an aircraft is supersonic, the pressure waves
cannot get away ahead of the aircraft as their natural speed is slower
than that of the aircraft. Slower, in this context, means just over
1200 km/hr at sea level and about 10% less at normal cruising altitude.
Because they cannot get away, the pressure disturbances coalesce and
lag behind the aeroplane, which is in effect travelling at the apex of
a conical shock wave. The main shock wave is generated by the extreme
nose of the aeroplane, but ancillary shocks are generated by all the
major fuselage discontinuities.
Ken Plotkin () on 24th July 1995 wrote:
[snip] .. A body moving through the air pushes the air aside. Small
disturbances move away at the speed of sound.
Disturbances from a
slowly moving body go out in circles, like ripples from a pebble in a
pond. If the body moves faster, the circles are closer in the direction
of travel. If the body is supersonic, then the circles overlap.
envelope of circles forms a cone.
The angle of the cone is determined
by its vertex moving in the body's travel direction at the body's
speed, while the circles grow at the sound speed.
existence of the "Mach cone", "Mach waves" and the corresponding angle,
was discovered by Ernst Mach in the nineteenth century. [snip]
Can you focus sound ?
Sound can be focused like light, but in the case of sound the "optics"
must be much larger because you are dealing with longer wavelengths.
The effect is heard in some domed buildings such as the Capitol in
Washington, and St Paul's Cathedral in London providing noise
background conditions permit.
Large parabolic reflectors can be used very effectively to send and
receive sound over significant distances. Check out your local science
museum or exploratorium - there may be a demonstration. It is also
possible to refract sound and focus it using a lens. The lens is
constructed from a large thin bubble, say 2 metres across, filled with
carbon dioxide. The effect is not very pronounced.
Sound can be directed by making use of constructive and destructive
interference. This idea is used in column speakers, and commercial
systems for reducing noise levels outside the dance floor area of
What is sonoluminescence ?
In the early 1930s Frenzel and Schultes discovered that photographic
plates became "fogged" when submerged in water exposed to high
frequency sound. More recent experiments have succeeded in suspending
a single luminous pulsating bubble in a standing wave acoustic field,
visible in an undarkened room. Generally sonoluminescence is light
emission from small cavitating bubbles of air or other gas in water or
other fluids, produced when the fluid is acted upon by intense high
frequency sound waves. The mechanism is not completely understood, but
very high pressures and temperatures are thought to be produced at the
centre of the collapsing bubbles.
See "Science" 14 October 1994 page 233, "Scientific American"
(International Edition) February 1995 Page 32 or "Physics Today"
September 1994 Page 22, all quite readable articles.
See also the following URLs:
http://ne43.ne.uiuc.edu/ans/sonolum.html
James Davison () on 28th June 1995 wrote:
[snip] .. I have been sufficiently interested to reconstruct the
apparatus for producing this effect -- using a pair of piezoelectric
transducers, an old oscilloscope and a signal wave generator --
materials costing only a few hundred dollars.
I am proud to say that tonight I managed to reproduce this effect --
the tiny bubble has the appearance of a tiny blue star trapped in the
middle of the flask.
It is distinctly visible to the unadapted eye in
a dark room, and it is a very startling thing to see. [snip]
Why does blowing over a bottle make a note ?
Resonance in acoustics occurs when some mass-spring combination is
supplied with energy. Many musical instruments rely on air resonance
to improve their sonority. If you blow across the mouth of a bottle you
can often get a note. The bottle behaves as a Helmholtz resonator. The
main volume of air inside the bottle is analogous to a spring, whilst
the "plug" of air in the neck acts as an attached mass. The resonant
frequency is roughly given by:
{ c sqrt (S/LV) } / 2pi
c is velocity of sound
S is the surface area of the neck opening
V is bottle volume
L is the effective length of the neck ie the actual length plus ends
correction. Ends correction ~ 1.5 times radius of neck opening
Example: A 75 cl (7.5E-4 m^3) wine bottle with neck diameter 19 mm,
bottle neck length 8 cm, air temp = 20 degC
calculated resonance = 109Hz (actual resonance was 105Hz)
Helmholtz resonators are sometimes employed as a means of passive noise
control in air conditioning ducts. They may also be hidden in the wall
design of auditoria and offices in order to improve the acoustics.
What is pitch ?
The term "pitch" has both a subjective and an objective sense.
Concert pitch is an objective term corresponding to the frequency of
a musical note A (at present 440Hz). Using such a standard will define
the pitch of every other note on a particular musical scale. For
example, with Equal Temperament each semitone is higher or lower in
frequency than the previous semitone by a factor of 2^(1/12). An octave
is a pitch interval of 2:1. Many sounds with no obvious tonal
prominence are considered by musicians to be of
for example, the side drum, cymbals, triangle, castanets, tambourine,
and likewise the spoken word.
Pitch is also a subjective frequency ordering of sounds. Perceived
pitch is dependent on frequency, waveform and amplitude or changing
amplitude. Numbers can be assigned to perceived pitch relative to a
pure frontal tone of 1000Hz at 40dB (1000 mels) thereby establishing
a pitch scale.
Further info and examples on pitch from URL:
http://www.music.mcgill.ca/auditory/Auditory.html
What are musical intervals ?
An interval is the ratio in frequency between musical notes. These
intervals are sometimes called a second, third, fourth, fifth etc.
which refers to the position on the scale that the note is to be found.
In the scale of C major: C D E F G A B C, the note 'E' is the third
note of the scale and the interval from C to E is therefore called a
third. For the scale D major: D E F# G A B C# D, the third will be F#.
The term 'interval' can also be used to indicate that the notes are
sounded together, in which case there are consonant intervals and
dissonant intervals.
The ratio of frequency intervals for Just Intonation is demonstrated
below in the scale of C major, though the same ratios apply to all the
major keys:
The interval between E & F and between B & C is a semitone, whilst the
other intervals are tones. The interval between any two notes above can
be found by multiplying th thus if all the above
ratios are multiplied together the resultant is 2 because an octave is
twice the original frequency.
The notes of minor scales differ from thei one
important difference being the flattened third. E flat is a minor third
above the note C.
The use of Just Temperament causes serious problems of intonation when
music modulates between keys. Equal Temperament is nearly always used
as a compromise to the problem of tuning (see question 6.6).
What causes "helium voice" ?
Many people, on hearing the voice of someone who has breathed helium,
believe that the person's speech pitch has increased.
WARNING - Breathing helium can be very dangerous.
A cavity will have certain resonant frequencies. These frequencies
depend on the shape and size of the cavity and on the velocity of sound
within the cavity. Human vocal cords vibrate non-sinusoidally in the
vocal tract, giving rise to a range of frequencies above the
fundamental. The vocal tract mainly enhances lower frequency components
imparting the recognizable voice spectrum.
The velocity of sound in helium is much greater than in air, so
breathing helium will raise the vocal tract's resonant frequencies.
Although the vocal cords' vibrational frequencies are little affected
by helium, the effect of higher cavity resonances is to alter
substantially the relative amplitudes of the voice spectrum components
thus leading to apparent pitch change.
What is structural acoustics ?
Structural acoustics is concerned with the coupled dynamic response of
elastic structures in contact with non-flowing fluids.
(The fluid,
although non-flowing, undergoes small-amplitude vibration relative to
some equilibrium position.)
For heavy fluids like water, the coupling
is two-way, since the structural response is influenced by the fluid
response, and vice versa.
For lighter fluids like air, the coupling
may be either one-way (where the structural vibration affects the fluid
response, but not vice versa) or two-way (as occurs, for example, in
the violin).
Structural acoustics problems of interest involving water include the
vibration of submerged structures, acoustic radiation from
mechanically-excited, submerged, acoustic
scattering from submerged, elastic structures (e.g., sonar echoes);
acou and dynamics of fluid-filled elastic
piping systems.
These problems are of interest for both time-harmonic
(sinusoidal) and general time-dependent (transient) excitations. Water
hammer in pipes can be thought of as a transient structural acoustics
Structural acoustics problems of interest involving air include
determining and reducing noise levels in automobile and airplane
Reference (for simple geometry problems):
"Sound, Structures, and Their Interaction," Second Edition, by M.C.
Junger and D. Feit, MIT Press, Cambridge, Mass (1986).
What is the doppler effect ?
When a sound source is moving, a stationary observer will detect a
different frequency to that which is produced by the source. The speed
of sound in air is approximately 340 m/s (see 2.11). The wavelength of
the sound emitted will be foreshortened in the direction of motion by
an amount proportional to the velocity of the source. Conversely the
wavelength of a receding sound source will increase. The doppler effect
may be noticed as a marked drop in pitch when a
vehicle passes at high
Example 1: A sound source, S, emits 1000 waves per second (1 kHz) and
is moving directly towards an observer, O, at a speed of 100 metres per
second (equivalent to approx 225 miles per hour).
After 1 second the wave front, which is travelling at the speed of
sound, will have travelled 340 metres from the original source
position. Also after that second the sound source will have moved 100
metres towards the observer.
&--------------
1000 waves
------------------&
1000 waves
---------&
Therefore the same number of waves will occupy a space of 340-100 = 240
metres and the wavelength will be 240/1000 = 0.24 metres.
To the observer the frequency heard will be the speed of sound divided
by its wavelength = 340/0.24 = 1416.7 Hz.
Example 2: An observer moving at 100 metres per second directly
approaches a stationary sound source, S, which is emitting 1000 waves
per second (1 kHz). In this example there is no change in wavelength.
In one second, the observer will hear the number of waves emitted per
second plus the number of waves which s/he has passed in the time
(.34) = 1294.1 Hz.
Note the interesting result - a stationary observer with moving source
will not hear the same frequency as a would a moving observer with
stationary source.
What is white noise, pink noise ?
The power spectral density of white noise is independent of frequency.
Since there is essentially the same energy between any two identical
frequency intervals (for example 84-86Hz and 543-545Hz), white noise
narrow band FFT analysis will show as flat. However octave band
analysis will show the level to rise by 3dB per octave because each
band has twice the frequency range of the preceding octave.
Pink noise is often produced by filtering white noise and has the same
power within each octave. Narrow band analysis will show a fall in
level with increasing frequency, but third-octave band or octave band
analysis will be flat.
see Joseph S. Wisniewski's Colors of noise FAQ at:-
http://capella.dur.ac.uk/doug/noisecols13.txt
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A-weighting 2.4 2.12 8.1
absorption coefficient 4.1 4.2
accelerometer 3.1
acoustic energy 2.1 2.8 2.10 4.1 4.3
Acoustical Society of America 2.4
active noise control 6.1
active vibration control 3.3
addition of sound 2.5
air absorption 2.9
atmospheric attenuation 2.9
atmospheric pressure 2.1 2.11
audibility 2.1 2.12
column speaker 6.3
concert pitch 6.6
dB(A) 2.4 8.1
decibel (dB) 2.2 2.3 2.4
Doppler effect 6.10
dynamic vibration absorber 3.3
ear 2.1 2.2 2.6 2.7
elastic structures 6.9
equal temperament 6.6 6.7
equivalent continuous sound level 2.4
focusing sound 6.3
frequency 2.1 2.4 2.12 6.6 6.7
hearing conservation 2.7 /~nhca/index.html
hearing damage 2.6 2.7
Helmholtz resonator 6.5
historical notes 2.4 2.12
insulation 4.3 4.4 4.5
interference 6.3
interval (music) 6.6 6.7
inverse square law 2.9
just intonation 6.7
logarithmic scale 2.2 2.3
loudness 2.1 2.2 2.12
loudspeaker 2.1 6.3
longitudinal wave 2.1
major and minor keys 6.7
masking 2.12
musical scale 6.6 6.7
ocean sound velocity 2.11
octave 6.6 6.11
pascal 2.1 2.2 2.8
passive noise control 6.1 6.5
peak level 2.3
physical constants
Pierce, George W 2.4
pink noise 6.11
pitch 6.6 6.8
resonance 6.5 6.8
reverberation time 4.1
Sabine, Wallace C 4.1
semitone 6.6 6.7
sonic boom 6.2
sonoluminescence 6.4
sound absorption 4.1 4.2 4.3
sound cancellation 6.1
sound decay 2.9
sound insulation 4.3 4.4 4.5
sound intensity 2.2 2.8
sound intensity meter 2.8
sound level 2.4 2.5 2.12
sound level meter 2.3 2.4 2.8 2.12
sound power level 2.10
sound pressure 2.1 2.2
sound pressure level 2.3 2.4 2.5
speech 6.6 6.8
speaker 2.1 6.3
speed of sound 2.1 2.11 6.8 6.10
structural acoustics 6.9
supersonic 6.2
tapping machine 4.4
third-octave band 6.11
tinnitus 2.6 2.7
ultrasound 2.9
ultrasound scans 2.7
velocity of sound 2.1 2.11 6.8 6.10
vibration 2.1 2.7 3.1,3.2
vibration control 3.3
voice 6.6 6.8
weighting 2.4 2.12 8.1
white finger 2.7
white noise 6.11
-------------------------------------------------------------
-------------------------------------------------------------
Various Tables
--------------
A weighting can be found from the following formulae
For A-weighting: A(f) =
12200^2 f^4
------------------------------------------------------------------
(f^2 +20.6^2) (f^2 +12200^2) (f^2 +107.7^2)^0.5 (f^2 +737.9^2)^0.5
The weighting in dB relative to 1000Hz is now given by
20 lg -------
note: A(1000) = 0.794
In tables, octave and third-octave frequencies are given as nominal
values, for example 1250 Hz or 2500 Hz. Ideally weightings should be
calculated for the exact frequencies which may be determined from the
formula 1000 x 10^(n/10), where n is a positive or negative integer.
Thus the frequency shown as 1250 Hz is more precisely 1258.9 Hz etc
-------------------------------------------------------------
List of National Acoustical Societies
-------------------------------------
For standards organizations addresses see section 1.2
Please let me know if any information in this list needs amending.
Argentina Acoustical Association
Asociacion de Acusticos Argentinos
c/o Prof A. Mendez, Laboratorio de Acustica, Camino Centenario Y 506,
1897 - Gonnet, Argentina
Tel: +54 21 84 2686
Fax: +54 21 71 2721
Australian Acoustical Society
Private Bag 1, Darlinghurst, NSW 2010
Tel: +61 2 331 6920
Fax: +61 2 331 7296
Austrian Acoustics Association
c/o Prof Ewald Benes, Technische Universitat Wien, Institut fur
Allgemeine Physik, Wien, Austria
Tel: +43 1
Fax: +43 1 5864203
Belgian Acoutics Assosciation (ABAV)
Av. P Holoffe 21, 1342 Limelette, Belgium
Tel: +32 2 653 88 01
Fax: +32 2 653 07 29
Sociedade Brasileira de Acustica
Attn Prof Samir Gerges, Universidade Federal de Santa Catarina,
Departamento de Engenharia Mecanica, Campus Univeritario, C.P 476
CEP , Florianopolis - SC, Brazil
Tel: +55 48 2344074
Fax: +55 48 2341519
Canadian Acoustical Association
PO Box 1351, Station F, Toronto, Ontario, M4Y 2V9, Canada
Tel: +1 514 343 7559
+1 613 993 0102
Sociedad Chilena de Acustica
San Francisco # 1138, Santiago, Chile.
Tel/Fax: +56 2 555 63 66 or +56 2 551 79 20
with copy (Cc) to:
China (PRC)
Acoustical Society of China
17 Zhongguancun St., Beijing 100080, China
Czech Republic
Czech Acoustical Society
Technicka 2, 166 27 Prague 6, Czech Republic.
Tel: +42 2
Fax: +42 2 3111786
Acoustical Society of Denmark
c/o Department of Acoustic Technology, Bldg. 352 - Technical University
of Denmark, DK-2800 Lyngby, Denmark
Acoustical Society of Finland
c/o Helsinki University of Technology, Acoustics Laboratory,
Otakaari 5 A, FIN-02150 Espoo, Finland
Tel: +358 9 451 2499
Fax: +358 9 460 224
French Acoustical Society
Societe Francaise d'Acoustique
23 avenue Brunetiere, 75017 Paris, France
Tel +33 1 48 88 90 59
Fax: +33 1 48 88 90 60
German Acoustical Society
Deutsche Gesellschaft fur Akustik
c/o Department of Physics Acoustics, University of Oldenburg,
D-26111 Oldenburg, Germany
Tel: +49 441 798 3572
Fax: +49 441 798 3698
Hellenic Acoustical Society
Patision 147, 112 51 Athens, Greece
Tel or Fax: +30 1
Hong Kong Institute of Acoustics
PO Box 7261
Scientific Society for Optics, Acoustics... (OPAKFI)
Fo utca 68, H-1027 Budapest, Hungary
Tel/Fax: +36 1 202 0452
e-mail (c/o Andras Illenyi):
Acoustical Society of India
c/o Dr S Agrawal, CEERI Centre, CSIR Complex, Hillside Road,
New Delhi-110012, India
Tel: +91 11 5784642
e-mail (c/o National Physical Lab):
Italian Association of Acoustics
Associazione Italiana di Acustica
via Cassia
Roma, Italy
Tel: +39 6
Fax: +39 6
Acoustical Society of Japan
Nippon Onkyo Gakkai
4th Floor, Ikeda Building, 2-7-7 Yoyogi, Shibuya-ku, Tokyo, Japan
Tel: +81 3
Fax: +81 3
Korean Republic
The Acoustical Society of Korea,
c/o 302-B, The Korean Federation of Science and Technology,
635-4, Yeoksam-dong, Kangnam-gu, Seoul-city, 135-080, Rep. of Korea
Tel: +82 2 565 1625
Fax: +82 2 569 9717
Mexican Institute of Acoustics
Instituto Mexicano de Acustica
c/o Sergio Beristain, P.O. BOX 75805,
Col. Lindavista 07300 Mexico, D.F.
Tel +52 5 682 28 30
Fax: +52 5 523 47 42
Netherlands
Netherlands Acoustical Society
Nederlands Akoestisch Genootschap
Postbus 162, NL-2600 AD, Delft, Netherlands
Tel: +31 15 26 92 442
Fax: +31 15 26 92 111
New Zealand
New Zealand Acoustical Society
J. Quedley, CPO Box 1181, Auckland, New Zealand
Tel: +64 9 623 3147
Fax: +64 9 623 3248
Acoustical Society of Norway
Norsk Akustisk Selskap
c/o Lydteknisk senter-NTH Sintef Delab, N-7034 Trondheim, Norway
Tel: +47 73 59 43 36
Fax: +47 73 59 14 12
Acoustical Society of Peru
Sociedad Peruana de Acustica
Garcilazo de la Vega 163, Salamanca de Monterrico, Lima 3, Peru
Tel: +51 1 4351151
Fax: +51 1 4675625
Polish Acoustical Society
Polskie Towarzystow Akustyki
Instytut Akustyki, Uniwersytet Adama Mikiewicz, ul J.Matejki 48/49,
60-769 Poznan, Poland
Tel or Fax: +48
Portuguese Acoustical Society
SPA - CAPS/Instituto Superior Tecnico, Av. Rovisco Pais
1096 Lisboa CODEX, Portugal
tel: +351 1 841 9393/39
fax: +351 1 352 3014
Romanian Acoustical Society
Societatea Romana de Acustica
c/o Nicolae Enescu, Universitatea Politehnica Bucuresti,
Splaiul Independentei nr. 313, 77206 Bucuresti, Romania
Tel: +40 1 4101615
Fax: +40 1 4104488
Russian Acoustical Society
4 Shvernik ul, Moscow, 117036 Russia
Tel: +7 095 126 7401
Fax: +7 095 126 8411
Singapore Acoustics Society
c/o W Gan, Acoustical Services Pte Ltd
209-212 Nanyang Ave, NTU, Singapore 2263
Fax +65 791 3665
Slovak Acoustical Society
c/o Prof Stefan Markus, Racianska 75, PO Box 95, 830 08 Bratislava 38,
Tel: +42 7 254751
Fax: +42 7 253301
South Africa
South African Acoustics Institute
c/o Dr Fred Anderson, P.O. Box 912-169, Silverton, South Africa, 0127
Tel or Fax: +27 12 832857
e-mail (c/o Andersen Technology):
Spanish Acoustical Society
Sociedad Espanola de Acustica
Serrano 144, E-28006 Madrid, Spain
Tel: +34 1 5618806
Fax: +34 1 4117651
Swedish Acoustical Society
Svenska Akustiska Sallskapet
c/o Ingemansson AB, Box 47 321
S-100 Stockholm, Sweden
Tel: +46 8 744 5780
Fax: +46 8 18 26 78
Switzerland
Schweizerische Gesellschaft fur Akustique
Societe Suisse d'Acoustique
Postfach 251, 8600 Dubendorf
Tel: +41 1 823 4743
Fax: +41 1 823 4793
Turkish Acoustical Society - TAS
Y.T.U. Mimarlik Fakultesi
Yildiz, 80750, ISTANBUL/TURKEY
Tel: +90 212 259 70 70 ext: 2772
Fax: +90 212 26105 49
Institute of Acoustics
5 Holywell Hill, St Albans, Herts, AL1 1EU, UK
Acoustical Society of America
500 Sunnyside Blvd., Woodbury, NY 11797, USA
Tel: +1 516 576 2360
Fax: +1 516 576 2377
-------------------------------------------------------------
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================
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Michael Carley ()
Gordon Everstine ()
Johan L Nielsen ()
Torben Poulsen ()
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Andrew Silverman (Enviro@measure.demon.co.uk)
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