Editing Acoustical engineering

{{Short description|Branch of engineering dealing with sound and vibration}}
'''Acoustical engineering''' (also known as '''acoustic engineering''') is the branch of [[engineering]] dealing with [[sound]] and [[oscillation|vibration]]. It includes the application of [[acoustics]], the science of sound and vibration, in technology. Acoustical engineers are typically concerned with the design, analysis and control of sound.

One goal of acoustical engineering can be the reduction of unwanted noise, which is referred to as [[noise control]]. Unwanted noise can have significant impacts on animal and human health and well-being, reduce attainment by students in schools, and cause hearing loss.<ref name="auto">{{cite book|last=World Health Organization|title=Burden of disease from environmental noise|year=2011|publisher=WHO|isbn=978-92-890-0229-5|url=http://www.euro.who.int/__data/assets/pdf_file/0008/136466/e94888.pdf}}</ref> Noise control principles are implemented into technology and design in a variety of ways, including control by redesigning sound sources, the design of noise barriers, sound absorbers, suppressors, and buffer zones, and the use of hearing protection ([[earmuffs]] or [[earplug]]s).

[[Image:Hamer Hall equipment detail.jpg|right|thumb|The transparent [[sound baffle|baffle]]s inside this auditorium were installed to optimise sound projection and reproduction, key factors in acoustical engineering.]]

Besides noise control, acoustical engineering also covers positive uses of sound, such as the use of [[medical ultrasound|ultrasound in medicine]], programming [[digital synthesizer]]s, designing concert halls to enhance the sound of orchestras<ref>{{cite book|last=Barron|first=Michael|title=Auditorium Acoustics and Architectural Design|year=2009|publisher=Taylor & Francis|isbn=978-0419245100}}</ref> and specifying railway station sound systems so that announcements are [[Intelligibility (communication)|intelligible]].<ref>{{cite book|last=Ahnert|first=Wolfgang|title=Sound Reinforcement Engineering: Fundamentals and Practice|year=2000|publisher=CRC Press |isbn=978-0415238700}}</ref>

== Acoustic engineer (professional) {{anchor|acoustic engineer}} ==

Acoustic engineers usually possess a [[bachelor's degree]] or higher qualification in [[acoustics]],<ref>{{cite web|last= Education in acoustics |title= MSc Engineering Acoustics, DTU |url=http://www.dtu.dk/english/Education/msc/Programmes/engineering_acoustics|access-date=9 February 2018}}</ref> [[physics]] or another [[engineering]] discipline. Practicing as an acoustic engineer usually requires a [[bachelor's degree]] with significant scientific and mathematical content. Acoustic engineers might work in acoustic consultancy, specializing in particular fields, such as [[architectural acoustics]], [[environmental noise]] or [[vibration control]].<ref>{{cite web|last=National Careers Service|title=Job profiles: Acoustics consultant|url=https://nationalcareersservice.direct.gov.uk/advice/planning/jobprofiles/Pages/acousticsconsultant.aspx|access-date=13 May 2013}}</ref> In other industries, acoustic engineers might: design [[automobile]] sound systems; investigate human response to sounds, such as urban soundscapes and domestic appliances; develop audio signal processing software for mixing desks, and design loudspeakers and microphones for mobile phones.<ref>{{cite web|last=University of Salford|title=Graduate Jobs in Acoustics|url=http://www.acoustics.salford.ac.uk/careers/index.php?content=roles|access-date=13 May 2013|archive-date=6 March 2016|archive-url=https://web.archive.org/web/20160306170213/http://www.acoustics.salford.ac.uk/careers/index.php?content=roles|url-status=dead}}</ref><ref>{{cite web|last=Acoustical Society of America|title=Acoustics and You|url=http://acousticalsociety.org/education_outreach/careers_in_acoustics|access-date=13 May 2013|archive-url=https://web.archive.org/web/20170308225726/http://acousticalsociety.org/education_outreach/careers_in_acoustics|archive-date=2017-03-08|url-status=dead}}</ref> Acousticians are also involved in researching and understanding sound scientifically. Some positions, such as [[faculty (academic staff)|faculty]] require a [[Doctor of Philosophy]].

In most countries, a degree in [[acoustics]] can represent the first step towards [[professional certification]] and the degree program may be certified by a [[professional body]]. After completing a certified degree program the engineer must satisfy a range of requirements before being certified. Once certified, the engineer is designated the title of [[Chartered Engineer]] (in most [[Commonwealth of Nations|Commonwealth]] countries).

==Subdisciplines==

The listed subdisciplines are loosely based on the PACS ([[Physics and Astronomy Classification Scheme]]) coding used by the [[Acoustical Society of America]].<ref>{{cite web|last=Acoustical Society of America|title=PACS 2010 Regular Edition—Acoustics Appendix|url=http://www.aip.org/pacs/pacs2010/individuals/pacs2010_regular_edition/reg_acoustics_appendix.htm|access-date=22 May 2013|archive-url=https://web.archive.org/web/20130514111126/http://www.aip.org/pacs/pacs2010/individuals/pacs2010_regular_edition/reg_acoustics_appendix.htm|archive-date=2013-05-14|url-status=dead}}</ref>

===Aeroacoustics===
{{main|Aeroacoustics}}

Aeroacoustics is concerned with how noise is generated by the movement of air, for instance via turbulence, and how sound propagates through the fluid air. Aeroacoustics plays an important role in understanding how noise is generated by [[aircraft]] and [[wind turbine]]s, as well as exploring how [[wind instrument]]s work.<ref>{{cite book|last=da Silva|first=Andrey Ricardo|title=Aeroacoustics of Wind Instruments: Investigations and Numerical Methods|year=2009|publisher=VDM Verlag|isbn=978-3639210644}}</ref>

===Audio signal processing===
{{main|Audio signal processing}}

Audio signal processing is the electronic manipulation of audio signals using [[Analog signal processing|analog]] and [[digital signal processing]]. It is done for a variety of reasons, including:
* to enhance a sound, e.g. by applying an audio effect such as [[reverberation]];
* to remove unwanted noises from a signal, e.g. [[echo cancellation]] in [[Voice over IP|internet voice calls]];
* to compress an audio signal to allow efficient transmission, e.g. perceptual coding in [[MP3]] and [[Opus (audio format)|Opus]] 
* to understand the content of the signal, e.g. identification of music tracks via [[music information retrieval]].<ref name="auto1">{{cite book|last=Pohlmann|first=Ken|title=Principles of Digital Audio, Sixth Edition|year=2010|publisher=McGraw Hill Professional|isbn=9780071663472|page=336}}</ref>

[[Audio engineers]] develop and use audio signal processing algorithms.

===Architectural acoustics===
{{main|Architectural acoustics}}
[[Image:Disney Concert Hall by Carol Highsmith.jpg|right|thumb|[[Walt Disney Concert Hall|Disney's Concert Hall]] was meticulously designed for superior acoustical qualities.]]
[[File:Heichal Hatarbut1.jpg|thumb|Ceiling of [[Culture Palace (Tel Aviv)]] concert hall is covered with [[perforated metal]] panels]]
Architectural acoustics (also known as '''building acoustics''') is the science and engineering of achieving a good sound within a building.<ref>{{cite book|last=Morfey|first=Christopher|title=Dictionary of Acoustics|year=2001|publisher=Academic Press|pages=32}}</ref> Architectural acoustics can be about achieving good speech intelligibility in a theatre, restaurant or railway station, enhancing the quality of music in a concert hall or recording studio, or suppressing noise to make offices and homes more productive and pleasant places to work and live.<ref>{{cite book|last=Templeton|first=Duncan|title=Acoustics in the Built Environment: Advice for the Design Team|year=1993|publisher=Architectural Press|isbn=978-0750605380}}</ref> Architectural acoustic design is usually done by acoustic consultants.<ref name="auto2">{{cite web|last=National Careers Service|title=Job profiles Acoustics consultant|url=https://nationalcareersservice.direct.gov.uk/advice/planning/jobprofiles/Pages/acousticsconsultant.aspx}}.</ref>

===Bioacoustics===
{{main|Bioacoustics}}

Bioacoustics concerns the scientific study of sound production and hearing in animals. It can include: acoustic communication and associated animal behavior and evolution of species; how sound is produced by animals; the auditory mechanisms and neurophysiology of animals; the use of sound to monitor animal populations, and the effect of man-made noise on animals.<ref name="bioacoustics">{{cite web|publisher=ASA|url=http://www.animalbioacoustics.org/bioacoustics.html|title=Acoustical Society of America Animal Bioacoustics Technical Committee. What is Bioacoustics? accessed 23 November 2017|access-date=22 May 2013|archive-date=6 June 2014|archive-url=https://web.archive.org/web/20140606141755/http://animalbioacoustics.org/bioacoustics.html|url-status=dead}}</ref>

===Electroacoustics===
<!-- This section is the target of the redirect [[Electroacoustics]]. Please do not rename without updating the link. -->
{{See also|Audio engineering|Sound reinforcement system|Transducer#electroacoustic}}
This branch of acoustic engineering deals with the design of headphones, [[microphone]]s, [[loudspeaker]]s, sound systems, sound reproduction, and recording.<ref>{{cite web|last=Acoustical Society of America|title=Acoustics and You (A Career in Acoustics?)|url=http://asaweb.devcloud.acquia-sites.com/education_outreach/careers_in_acoustics|access-date=21 May 2013|archive-url=https://web.archive.org/web/20150904010934/http://asaweb.devcloud.acquia-sites.com/education_outreach/careers_in_acoustics|archive-date=2015-09-04|url-status=dead}}</ref> There has been a rapid increase in the use of portable electronic devices which can reproduce sound and rely on electroacoustic engineering, e.g. [[mobile phone]]s, [[portable media player]]s, and [[tablet computer]]s.

The term "electroacoustics" is also used to describe a set of electrokinetic effects that occur in heterogeneous liquids under influence of ultrasound.<ref name="dukhin2002">Dukhin, A.S. and Goetz, P.J. [https://dispersion.com/books/ "Characterization of liquids, nano- and micro- particulates and porous bodies using Ultrasound"], Elsevier, 2017 
{{ISBN|978-0-444-63908-0}}</ref><ref>[https://www.iso.org/standard/52807.html ISO International Standard 13099, Parts 1,2 and 3, "Colloidal systems – Methods for Zeta potential determination", (2012)]</ref>

===Environmental noise===
{{main|Environmental noise}}
{{See also|Noise pollution|Noise control}}
[[Image:Woodstock 2007.jpg|right|thumb|At outdoor concerts like [[Woodstock Festival (Poland)|Woodstock]], acoustic analysis is critical to creating the best experience for the audience and the performers.]]
Environmental acoustics is concerned with the control of noise and vibrations caused by traffic, aircraft, industrial equipment, recreational activities and anything else that might be considered a nuisance.<ref name="auto"/> Acoustical engineers concerned with environmental acoustics face the challenge of measuring or predicting likely noise levels, determining an acceptable level for that noise, and determining how the noise can be controlled. Environmental acoustics work is usually done by acoustic consultants or those working in [[environmental health]].<ref name="auto2"/> Recent research work has put a strong emphasis on [[soundscape]]s, the positive use of sound (e.g. fountains, bird song), and the preservation of [[tranquility]].<ref>{{cite book|last=Kang|first=Jian|title=Urban Sound Environment|year=2006|publisher=CRC Press|isbn=978-0415358576}}</ref>

===Musical acoustics===
{{main|Musical acoustics}}

Musical acoustics is concerned with researching and describing the physics of music and its perception – how [[sound]]s employed as [[music]] work. This includes: the function and design of [[musical instrument]]s including electronic [[synthesizers]]; the human voice (the [[physics]] and [[neurophysiology]] of [[singing]]); computer analysis of music and composition; the clinical use of music in music therapy, and the perception and cognition of [[music]].<ref>{{cite web|last=Technical Committee on Musical Acoustics (TCMU) of the Acoustical Society of America (ASA)|url=http://www.public.coe.edu/~jcotting/tcmu/|title=ASA TCMU Home Page|access-date=22 May 2013|archive-url=https://web.archive.org/web/20010613120620/http://www.public.coe.edu/~jcotting/tcmu/|archive-date=2001-06-13|url-status=dead}}</ref>

===Noise control===
{{main|Noise control}}

Noise control is a set of strategies to reduce [[noise pollution]] by reducing noise at its source, by inhibiting sound propagation using [[noise barrier]]s or similar, or by the use of ear protection ([[earmuffs]] or [[earplug]]s).<ref>{{cite book|last=Bies|first=David|title=Engineering Noise Control: Theory and Practice|year=2009|publisher=Spon Press/Taylor & Francis |isbn=978-0415487078}}</ref> Control at the source is the most cost-effective way of providing noise control. Noise control engineering applied to cars and trucks is known as [[noise, vibration, and harshness]] (NVH). Other techniques to reduce product noise include [[vibration isolation]], application of acoustic absorbent and acoustic enclosures. Acoustical engineering can go beyond noise control to look at what is the best sound for a product,<ref>{{cite web|last=University of Salford|title=Making products sound better|url=http://www.acoustics.salford.ac.uk/res/cox/sound_quality/|access-date=2013-05-21|archive-url=https://web.archive.org/web/20130724080408/http://www.acoustics.salford.ac.uk/res/cox/sound_quality/|archive-date=2013-07-24|url-status=dead}}</ref> for instance, manipulating the sound of door closures on [[automobile]]s.

===Psychoacoustics===
{{main|Psychoacoustics}}

Psychoacoustics tries to explain how humans respond to what they hear, whether that is an annoying noise or beautiful music. In many branches of acoustic engineering, a human listener is a final arbitrator as to whether a design is successful, for instance, whether [[sound localisation]] works in a [[surround sound]] system. "Psychoacoustics seeks to reconcile acoustical stimuli and all the scientific, objective, and physical properties that surround them, with the physiological and psychological responses evoked by them."<ref name="auto1"/>

===Speech===
{{main|Speech}}

Speech is a major area of study for acoustical engineering, including the production, processing and perception of speech. This can include [[physics]], [[physiology]], [[psychology]], [[audio signal processing]] and [[linguistics]]. [[Speech recognition]] and [[speech synthesis]] are two important aspects of the machine processing of speech. Ensuring [[speech transmission index|speech is transmitted intelligibly]], efficiently and with high quality; in rooms, through public address systems and through telephone systems are other important areas of study.<ref>{{cite web|last=Speech Communication Technical Committee|title=Speech Communication|url=http://acosoc.org/TechComm/SCTC/|publisher=Acoustical Society of America|access-date=22 May 2013|archive-date=4 June 2013|archive-url=https://web.archive.org/web/20130604013140/http://acosoc.org/TechComm/SCTC/|url-status=dead}}</ref>

===Ultrasonics===
{{main|Ultrasound}}
[[File:CRL Crown rump length 12 weeks ecografia Dr. Wolfgang Moroder.jpg|thumb|right|Ultrasound image of a fetus in the womb, viewed at 12 weeks of pregnancy (bidimensional-scan)]]Ultrasonics deals with sound waves in solids, liquids and gases at frequencies too high to be heard by the average person. Specialist areas include medical ultrasonics (including [[medical ultrasonography]]), [[sonochemistry]], [[nondestructive testing]], material characterisation and [[underwater acoustics]] ([[sonar]]).<ref>{{cite book|last=Ensminger|first=Dale|title=Ultrasonics: Fundamentals, Technologies, and Applications|year=2012|publisher=CRC Press|pages=1–2}}</ref>

===Underwater acoustics===
{{main|Underwater acoustics}}

Underwater acoustics is the scientific study of sound in water. It is concerned with both natural and man-made sound and its generation underwater; how it propagates, and the perception of the sound by animals. Applications include [[sonar]] to locate submerged objects such as [[submarines]], underwater communication by animals, observation of sea temperatures for climate change monitoring, and marine biology.<ref>{{cite web|last=ASA Underwater Acoustics Technical Committee |title=Underwater Acoustics |url=http://www.apl.washington.edu/projects/ASA-UATC/index.php |access-date=22 May 2013 |url-status=dead |archive-url=https://web.archive.org/web/20130730104616/http://www.apl.washington.edu/projects/ASA-UATC/index.php |archive-date=30 July 2013 }}</ref>

===Vibration and dynamics===
{{main|Vibration}}

Acoustic engineers working on vibration study the motions and interactions of mechanical systems with their environments, including measurement, analysis and control. This might include: [[ground vibrations]] from railways and construction; [[vibration isolation]] to reduce noise getting into recording studios; studying the effects of vibration on humans ([[vibration white finger]]); [[vibration control]] to protect a bridge from [[earthquakes]], or modelling the propagation of structure-borne sound through buildings.<ref>{{cite web|last=Structural Acoustics & Vibration Technical Committee |title=Structural Acoustics & Vibration Technical Committee |url=http://fubini.swarthmore.edu/~bbard/savtc.html |access-date=22 May 2013 |url-status=dead |archive-url=https://web.archive.org/web/20131103180745/http://fubini.swarthmore.edu/~bbard/savtc.html |archive-date=3 November 2013 }}</ref>

==Fundamental science==

Although the way in which sound interacts with its surroundings is often extremely complex, there are a few ideal sound wave behaviours that are fundamental to understanding acoustical design.  Complex sound wave behaviors include [[Absorption (acoustics)|absorption]], [[reverberation]], [[diffraction]], and [[refraction]]. Absorption is the loss of energy that occurs when a sound wave reflects off of a surface, and refers to both the sound energy transmitted through and dissipated by the surface material.<ref>Barron, 2002, ch. 7.1.</ref> Reverberation is the persistence of sound caused by repeated boundary reflections after the source of the sound stops. This principle is particularly important in enclosed spaces. Diffraction is the bending of sound waves around surfaces in the path of the wave. Refraction is the bending of sound waves caused by changes in the medium through which the wave is passing. For example, temperature gradients can cause sound wave refraction.<ref>Hemond, 1983, pp. 24–44.</ref> Acoustical engineers apply these fundamental concepts, along with mathematical analysis, to control sound for a variety of applications.

== Associations ==

*[https://tceaasa.org/ Acoustical Society of America Technical Committee on Engineering Acoustics]
*[[Audio Engineering Society]]
*[[Australian Acoustical Society]]<ref>{{cite web|url=https://www.acoustics.asn.au/joomla/|title=Australian Acoustical Society ABN 28 000 712 658 A.C.N. 000 712 658|website=www.acoustics.asn.au}}</ref>
*[[Canadian Acoustical Association]]<ref>{{cite web|url=http://caa-aca.ca|title=Canadian Acoustics - Acoustique Canadienne|website=caa-aca.ca}}</ref>
* [[Institute of Acoustics, Chinese Academy of Sciences]]
* [[Institute of Acoustics (United Kingdom)]]
*[https://danishsoundcluster.dk/en/ Danish Sound Cluster (Denmark)]

== See also ==
*[[Audio Engineering]]
*[[:Category:Acoustical engineers]]
*[[:Category:Audio engineers]]

==References==
{{Reflist}}

*Barron, R. (2003). ''Industrial noise control and acoustics''. New York: Marcel Dekker Inc. Retrieved from CRCnetBase
*Hemond, C. (1983). In Ingerman S. ( Ed.), ''Engineering acoustics and noise control''. New Jersey: Prentice-Hall.
*''Highway traffic noise barriers at a glance''. Retrieved February 1, 2010, from http://www.fhwa.dot.gov/environment/keepdown.htm {{Webarchive|url=https://web.archive.org/web/20110615145225/http://www.fhwa.dot.gov/environment/keepdown.htm |date=2011-06-15 }}
*Kinsler, L., Frey, A., Coppens, A., & Sanders, J. (Eds.). (2000). ''Fundamentals of acoustics'' (4th ed.). New York: John Wiley and Sons.
*Kleppe, J. (1989). ''Engineering applications of acoustics''. Sparks, Nevada: Artech House.
*Moser, M. (2009). ''Engineering acoustics'' (S. Zimmerman, R. Ellis Trans.). (2nd ed.). Berlin: Springer-Verlag.

{{Engineering fields}}
{{Acoustics}}
{{Authority control}}

[[Category:Acoustics]]
[[Category:Noise reduction]]
[[Category:Engineering disciplines]]
[[Category:Sound]]
[[Category:Noise control]]