Editing Microphonics

{{Redirect|Microphony|the similarly titled compositions by Karlheinz Stockhausen|Mikrophonie}}
{{Redirect|Valve hammer|the level editor|Valve Hammer}}
{{Use dmy dates|date=January 2020|cs1-dates=y}}

[[File:Ultraii2.jpg|thumb|Audio vacuum tube with externally fitted microphonics damper]]

'''Microphonics''', '''microphony''', or '''microphonism'''<ref name="ActaTechnica_1956"/><ref name="Korn_1956"/><ref name="Electronics_1956"/> describes the phenomenon wherein certain components in [[Electronics|electronic]] devices transform mechanical [[vibration]]s into an undesired electrical signal ([[noise (electronics)|noise]]). The term comes from analogy with a [[microphone]], which is intentionally designed to convert vibrations to electrical signals.

==Description==
When electronic equipment was built using [[vacuum tube]]s, microphonics were often a serious design problem. The charged elements in the vacuum tubes can mechanically vibrate, changing the distance between the elements, producing charge flows in and out of the tube in a manner identical to a capacitor microphone. A system sufficiently susceptible to microphonics could experience [[audio feedback]], and make noises if jarred or bumped. To minimize these effects, some vacuum tubes were made with thicker internal insulating plates and more supports,<ref name="Tomer_1960"/> and tube-socket assemblies were sometimes [[shock-mount]]ed  by means of small [[rubber grommet]]s placed in the screw holes to isolate them from vibration.<ref name="Korn_1956"/>

[[File:Valve hammer.jpg|thumb|Radio and TV repairman's tool for testing microphony in vacuum tubes. The black rubber grommet gives the tube a firm but safe impact. Pen for scale.]]
A special tool, called a valve hammer, or tube hammer was sometimes used to safely tap the device suspected of being microphonic, while it was operating, so checking if such a tap would produce objectional audio effects.<ref name="ActaTechnica_1956"/>

Microwave tube designers took numerous steps to reduce microphonics in [[klystron]]s. Where tuning was essential, a compromise usually was made between the resistance of the klystron to microphonism and the obtainable performance.<ref name="Electronics_1956"/>

With the advent of [[solid-state electronics]] ([[transistor]]s), this major source of microphonics was eliminated but smaller sources still remain.

The [[ceramic]] [[EIA Class 2 dielectric]]s used in [[high-κ]] [[capacitor]]s ("[[Z5U]]" and "[[X7R]]") are [[piezoelectric]] and directly transform mechanical vibration into a voltage in exactly the same way as a ceramic or piezoelectric microphone.<ref name="Kemet_2007"/> [[Film capacitor]]s using soft (mechanically compliant) [[dielectric]] materials can also be microphonic due to vibrational energy physically moving the plates of the capacitor{{Citation needed|reason=unable to find source. might be original research.|date=August 2018}}. Likewise, variable capacitors using air as a dielectric are vulnerable to vibrations moving the plates. Capacitors using [[glass]] as the dielectric, while quite expensive, can be made to be essentially non microphonic.

Wiring, cables and even [[printed circuit board]]s (PCB) can also exhibit microphonics as charged conductors move around, and various materials can develop [[triboelectric]] charges (a type of [[static electricity]]) that couple to the electronic circuits.

[[Guitar amplifier]]s that incorporate the electronic [[chassis]] into the same cabinet as the speaker are susceptible to microphonics. Though a guitar amplifier's microphonics distortion is sometimes appreciated as part of the "special sound" of a guitar amplifier, a faulty vacuum tube or other component can cause out-of-control [[positive feedback]]. Unwanted microphonics-related audible distortions can often be alleviated by using commercially available vacuum tube mechanical dampers.

The term may also be used to describe a video artifact common in older video cameras. Before the introduction of solid-state [[charge-coupled device]] (CCD) sensors to produce the image, [[Video camera tube|vacuum tubes]] performed this task. Loud noises in the studio, such as rock bands or gunshot effects would cause the tubes to vibrate, producing a characteristic undesirable horizontal banding in the image.<ref name="Demtschyna_2002"/>

The effect can also be observed when operating a [[record player]] in the same room as the loudspeakers. Depending on the construction of the player the sound may acoustically couple into the record player's dust cover or other mechanical parts and cause a feedback loop into the pickup cartridge.

Many [[In-ear monitor]]s exhibit microphonics when headphone cables transfer vibrations due to cable movement directly to the wearers ears.<ref name="Frakes_2007"/>

== See also ==
* [[Audio spill]]
* [[Cable grommet]]
* [[Crosstalk]]
* [[Ringing (signal)]]

== References ==
{{Reflist|30em|refs=
<ref name="ActaTechnica_1956">{{cite book |title=Acta Technica - Academiae Scientiarum Hungaricae |author-first=Iván Péter |author-last=Valkó |author-link=:hu:Valkó Iván Péter |volume=15 |date=1956 |publisher=[[Magyar Tudományos Akadémia]] |location=Budapest, Hungaria |pages=229–231 |url=https://books.google.com/books?id=dKAIAQAAIAAJ |access-date=2013-04-17}}</ref>
<ref name="Korn_1956">{{cite book |author-first1=Granino Arthur |author-last1=Korn |author-first2=Theresa M. |author-last2=Korn |title=Electronic analog computers (d-c analog computers) |date=1956 |edition=2 |publisher=[[McGraw-Hill]] |pages=157, 248–249 |url=https://books.google.com/books?id=l4BQAAAAMAAJ |access-date=2013-04-17}}</ref>
<ref name="Electronics_1956">{{cite book |title=Electronics |chapter=Nonmicrophonic Klystron |author-first=Roger A. |author-last=La Plante |location=Philips Laboratories, Irvington-on-Hudson, NY, USA |volume=29 |date=July 1956 |publisher=[[McGraw-Hill Publishing Company]] |pages=238, 241 |url=https://books.google.com/books?id=_DkjAQAAMAAJ |access-date=2013-04-17}}</ref>
<ref name="Tomer_1960">{{cite book |author-first=Robert B. |author-last=Tomer |title=Getting the most out of Vacuum Tubes |chapter=Chapter 3: Subjective Failures: Microphonics |pages=48–50 |publisher=[[Howard W. Sams & Co., Inc.]] |series=Photofact Publication |location=Indianapolis, USA |date=July 1960 |edition=first printing, first |id=VTT-1 |lccn=60-13843 |url=http://www.tubebooks.org/Books/Atwood/Tomer%201960%20Getting%20the%20Most%20Out%20of%20Vacuum%20Tubes.pdf |access-date=2020-01-31 |url-status=live |archive-url=https://web.archive.org/web/20190715223356/http://tubebooks.org/Books/Atwood/Tomer%201960%20Getting%20the%20Most%20Out%20of%20Vacuum%20Tubes.pdf |archive-date=2019-07-15}} [https://archive.org/details/Tomer_1960_Getting_the_Most_Out_of_Vacuum_Tubes/mode/2up]</ref>
<ref name="Demtschyna_2002">{{cite web |title=Video Artefacts - Microphony |author-first=Michael |author-last=Demtschyna |work=Michael D's DVD |date=2002 |url=http://www.michaeldvd.com.au/Articles/VideoArtefacts/VideoArtefactsMicrophony.html |access-date=2020-01-31 |url-status=live |archive-url=https://web.archive.org/web/20190611185854/http://www.michaeldvd.com.au/Articles/VideoArtefacts/VideoArtefactsMicrophony.html |archive-date=2019-06-11}}</ref>
<ref name="Kemet_2007">{{cite web |title=Capacitors for Reduced Microphonics and Sound Emission  |author-first1=Mark |author-last1=Laps |author-first2=Roy |author-last2=Grace |author-first3=Bill |author-last3=Sloka |author-first4=John |author-last4=Prymak |author-first5=Xilin |author-last5=Xu |author-first6=Pascal |author-last6=Pinceloup |author-first7=Abhijit |author-last7=Gurav |author-first8=Michael |author-last8=Randall |author-first9=Philip |author-last9=Lessner |author-first10=Aziz |author-last10=Tajuddin |publisher=[[KEMET Electronics Corporation]], Electronic Components, Assemblies & Materials Association (ECA), Arlington, VA. |date=March 2007 |series=CARTS 2007 Symposium Proceedings |location=Albuquerque, NM, USA |url=http://www.kemet.com/kemet/web/homepage/kfbk3.nsf/vaFeedbackFAQ/118EBDDDFA5D532C852572BF0046B776/$file/2007%20CARTS%20-%20Reduced%20Microphonics%20and%20Sound%20Emissions.pdf |access-date=2020-01-31 |url-status=live |archive-url=https://web.archive.org/web/20191116171801/http://www.kemet.com/Lists/TechnicalArticles/Attachments/62/2007%20CARTS%20-%20Reduced%20Microphonics%20and%20Sound%20Emissions.pdf |archive-date=2019-11-16}} (8 pages)</ref>
<ref name="Frakes_2007">{{cite web |title=In-ear-canal headphone primer |author-first=Dan |author-last=Frakes |series=Headsets |journal=[[Macworld]] |publisher=[[IDG]] |date=2007-01-31 |url=http://www.macworld.com/article/55152/2007/01/canalphones.html |access-date=2020-01-31 |url-status=live |archive-url=https://web.archive.org/web/20190328053228/https://www.macworld.com/article/1055152/canalphones.html |archive-date=2019-03-28}}</ref>
}}

== External links ==
* [http://www.thevalvepage.com/valvetek/microph/microph.htm Valve microphonics] at The Valve Page

[[Category:Electronic design]]
[[Category:Radio technology]]
[[Category:Microphones]]