Automixer

Automixers balance multiple sound sources based on each source's level, quickly and dramatically adjusting the various signal levels automatically.{{cite web|url=http://www.aes.org/par/a/#automatic_mic_mixer |title=AES Pro Audio Reference; |publisher=AES |accessdate=2017-12-17 }} Automixers are used in live sound reinforcement to maintain a steady limit on the overall signal level of the microphones; if a public address system is set up so that one microphone will not feed back, then, in general, the automixer will prevent feedback when multiple microphones are used. The equivalent number of open mics (NOM) present at the output of the automixer is kept low, regardless of the actual number of mics in use.{{cite web|url=http://svconline.com/ar/avinstall_right_mix_applications/ |archive-url=https://web.archive.org/web/20110716171307/http://www.svconline.com/ar/avinstall_right_mix_applications/ |archive-date=2011-07-16 |title=The Right Mix: The applications of automatic microphone mixers are numerous and varied; know when and how to use them properly |date=January 1998 |publisher=Sound & Video Contractor |author=Dan Dugan}}

While a skilled mixing engineer can greatly enhance the performance of a sound reinforcement system they cannot anticipate with perfect accuracy which participant will speak next in a spontaneous discussion. Sudden interjections by panelists may be lost completely, or the beginning of a word may be absent (or upcut{{cite web |url=https://training.npr.org/audio/butt-cut-what-a-glossary-of-production-terms/ |title='Butt cut what?' A glossary of audio production terms and definitions |author=ALISON MACADAM |date=June 1, 2015 |access-date=2019-04-16}}) because the operator does not respond quickly enough.{{cite web|url=http://complicationsensue.blogspot.com/2006/03/upcut.html |title=UPCUT |date=March 8, 2006 |accessdate=2011-03-12}} A properly adjusted automixer can prevent losing words or phrases due to upcut mistakes or lapses of attention.{{cite web|url=https://peavey.com/support/technotes/mixers/automix.pdf |title=Automatic Mixers |author1=Tom Stuckman |author2=Steve Marks |format=PDF |accessdate=2019-03-20}}

Priority ducking is used to lower the level of a microphone or program material, based on a signal at a source microphone, for the duration of the signal present at the source microphone. It restores the original level once the source microphone signal has ceased. This is useful when program material needs to be attenuated in order to accentuate the voice of a narrator or if one microphone is used by a chairman or master of ceremonies and needs to have priority over other mics or program material, or if a paging mic must attenuate all other signals.

Automixers can be oriented toward live reinforcement applications or permanent installation. Live applications typically use XLR connectors and external controls. For permanent installations euroblock connectors and tamper-resistant internal controls may be used. Channel configuration switches select sensitivity (dynamic mic, condenser mic, or line level), enable or disable phantom power, set priority, and select always-on or auto mode (always-on being useful for uninterrupted music playback). Auto mixers are frequently used in boardrooms but are also useful in theatrical productions and town hall meetings where several wireless microphones are in use. Auto mixers may be connected directly to wired mics and wireless mic receivers or may be connected to the insert of a mixing console. Integration of an auto mixer with manual mixing console permits more precise input gain control, absolute mic muting, low cut filter and other equalization and individual mic channel foldback control.

Frank J. Clement and Bell Labs received a patent in 1969 for a multiple-station conference telephone system that switched its output to the loudest input.{{Cite patent|country=US|number=3437758|pubdate=1969-04-08|title=Conference telephone system|assign1=Bell Telephone Laboratories Inc.|inventor1-last=Clement|inventor1-first=Frank J.}} The next year, Emil Torick and Richard G. Allen were granted a patent for an "Automatic Gain Control System with Noise Variable Threshold", an adaptive threshold circuit invention with its patent assignation going to Columbia Broadcasting System.{{Cite patent|country=US|number=3496481|pubdate=1970-02-17|title=Automatic gain control system with noise variable threshold|assign1=Columbia Broadcasting System, Inc.|inventor1-last=Torick|inventor1-first=Emil|inventor2-last=Allen|inventor2-first=Richard G.}}

Some systems using electro-mechanical switching for microphone activation were engineered in the late 1960s and early 1970s. Peter W. Tappan and Robert F. Ancha devised a system of seat sensors that would activate one of 350 hidden microphones at the Seventeenth Church of Christ, Scientist in Chicago in 1970.{{Cite patent|country=US|number=3538254|pubdate=1970-11-03|title=Automatic sound system with a plurality of microphones|assign1=Ancha Electronics Inc.|inventor1-last=Ancha|inventor1-first=Robert F.}} From approximately 1968, Ken Patterson and Diversified Concepts developed a hardware system that could detect the number of open microphones (NOM) and attenuate the master output by an amount which increased with a higher number of microphones in use. This latter system was public domain.{{cite journal|author=Dan Dugan |url=http://www.aes.org/e-lib/browse.cfm?elib=5859 |title=Application of Automatic Mixing Techniques to Audio Consoles |date=October 1989 |publisher=Audio Engineering Society |accessdate=2011-03-12}}

In 1971, Gregory Maston of Bell Labs filed for a patent involving a circuit that could switch between several audio sources based on their levels. The loudest one was latched into the mix. This system did not ramp switched signals smoothly in and out and did not maintain a constant ambient noise level. It was intended for speakerphone conferencing applications.{{Cite patent|country=US|number=3755625|pubdate=1973-08-28|title=Multimicrophone loudspeaking telephone system|assign1=Bell Telephone Laboratories Inc.|inventor1-last=Maston|inventor1-first=Donald James}} In 1972, Keith A. T. Knox with the British Post Office Corporation developed an adaptive threshold gate circuit intended for speakerphone usage. The system used a second microphone somewhat near the first to sense ambient noise level.{{Cite patent|country=CA|number=893261|pubdate=1972-02-15|title=Telecommunication systems|assign1=Post Office|inventor1-last=Knox|inventor1-first=Keith A. T.}}

File:Dugan automixers - Dugan Model A8 and A6, and prototype.jpg first automixers]]

Dan Dugan showed his first Adaptive Threshold Automatic Microphone Mixing System in 1974 at the 49th Audio Engineering Society (AES) meeting in New York,{{cite journal|author=Dugan, Daniel W. |url=http://www.aes.org/e-lib/browse.cfm?elib=5643 |title=Adaptive Threshold Automatic Microphone Mixing System Becomes Public Domain |publisher=Audio Engineering Society |date=February 1991 |accessdate=2011-03-12}} and was granted a patent for a control apparatus for sound reinforcement systems which sensed ambient sound level in the environment of a theater to control each microphone's level.{{US patent reference |number=3814856 |y=1974 |m=06 |d=04 |inventor=Dan Dugan |title=Control Apparatus for Sound Reinforcement Systems}} In 1976, Dugan was granted a patent for an automatic microphone mixing process whereby the total gain of the system remains constant.{{US patent reference |number=3992584 |y=1976 |m=11 |d=16 |inventor=Dan Dugan |title=Automatic Microphone Mixer}} He began manufacturing his first automixer system, the Model A, based on his two patents. Dugan built 60 units, with the first, hand-assembled one taken to Bell Labs to be installed in their conference room for Harvey Fletcher.{{cite web|author=Shannon Slaton |url=http://livedesignonline.com/gear/sound/sound_product_month_3/ |title=Sound Product of the Month: Dugan Model E-1 Automatic Mixing Controller |publisher=Livedesignonline.com |date=June 1, 2008 |accessdate=2011-03-12}} The algorithm was simple and effective: "Each individual input channel is attenuated by an amount, in dB, equal to the difference, in dB, between that channel's level and the sum of all channel levels."{{cite web|url=http://www.protechaudio.com/products/PDFFiles/DuganMixing.pdf |publisher=Protech Audio |title=The Path Less Taken – Dugan Automixing |format=PDF |accessdate=2011-03-12}} Dugan licensed the system to Altec which released several automixer models including the 1674A, -B and -C series and the 1684A, all focusing on speech applications.{{cite web|url=http://www.vintagealtecinfo.com/Altec%20MIXER3%201674C%201678C%20Automatic%20Microphone%20Mixers.html |title=1674C & 1678C Automatic Microphone Mixers |accessdate=2011-03-12}}{{cite web|url=http://www.vintagealtecinfo.com/Altec%20MIXER2%201684A%20Expandable%20Automatic%20Microphone%20Mixer.html |title=1684A Expandable Automatic Microphone Mixer |accessdate=2011-03-12}} The earliest Altec product implementation was regarded as inferior within the commercial audio contractor industry, and other manufacturers began to design their own automixer products.

In 1978, Richard W. Peters of Industrial Research Products (IRP) was granted an improvement patent entitled "Priority mixer control".{{Cite patent|country=US|number=4149032|pubdate=1979-04-10|title=Priority mixer control|assign1=Industrial Research Products Inc.|inventor1-last=Peters|inventor1-first=Richard W.}} IRP released the Voice-Matic series of {{resx|4×1}} and {{resx|8×1}} automatic mixers using "Dynamic Threshold Sensing" that weighed a combination of the amplitude and history of the signal to determine channel access. The master output was attenuated at the rate of 3 dB for every doubling of NOM.{{cite web |url=http://www.irp.net/html/sub5/automaticmixer.html |title=Automatic Mixers Voice-Matic |publisher=Industrial Research Products |accessdate=2011-03-12 |archive-url=https://web.archive.org/web/20080720182257/http://www.irp.net/html/sub5/automaticmixer.html |archive-date=July 20, 2008 |url-status=dead |df=mdy-all }} This master output reduction was the solution used by Yamaha Pro Audio two decades later in their DME series of digital signal processing (DSP) products, incorporating an automixer function which was otherwise an 8- or 16-channel noise gate.{{cite web|url=http://www2.yamaha.co.jp/manual/pdf/pa/english/signal/dmedesigner_en_om_v351a.pdf|title=DME Designer Owner's Manual, version 3.5|year=2004|publisher=Yamaha Pro Audio|pages=421–424|accessdate=June 25, 2010|archive-url=https://web.archive.org/web/20110716055614/http://www2.yamaha.co.jp/manual/pdf/pa/english/signal/dmedesigner_en_om_v351a.pdf|archive-date=July 16, 2011|url-status=dead}}

Eugene Campbell and Terrance Whittemore of Colorado were granted a patent in 1982 for an automatic microphone mixing algorithm that allowed for musical performance mixing that would not be dominated by the loudest vocalist or instrumentalist.{{Cite patent|country=US|number=4357492|pubdate=1982-11-02|title=Automatic microphone mixing apparatus|inventor1-last=Campbell|inventor1-first=Eugene|inventor2-last=Whittemore|inventor2-first=Terrance R.}}

File:Automix 4 graphic user interface.png

Stephen D. Julstrom of Shure Brothers Incorporated was granted a patent in 1987 for a teleconferencing system that used special directionally gated microphones mixed automatically and sent to a distant party via telephone line. The return signal from the distant party was compared in strength to the local mix to determine which party was to be most prominent in the overall mix. Any interrupting party was given priority.{{Cite patent|country=US|number=4712231|pubdate=1987-12-08|title=Teleconference system|assign1=Shure Brothers Inc.|inventor1-last=Julstrom|inventor1-first=Stephen D.}} Four years later, Shure would introduce the AMS4000 and AMS8000 automixers for sound reinforcement; mixers which required the use of special directional condenser microphones of the Shure AMS Series.{{citation |url=http://cdn.shure.com/user_guide/upload/652/us_pro_ams8000_ug_27a8273_qc_.pdf |title=AMS4000 and AMS8000 Installer's Manual |publisher=Shure |accessdate=2015-04-02 |archive-url=https://web.archive.org/web/20150909210909/http://cdn.shure.com/user_guide/upload/652/us_pro_ams8000_ug_27a8273_qc_.pdf |archive-date=September 9, 2015 |url-status=dead |df=mdy-all }}

In 1985 Innovative Electronic Designs (IED) introduced the circuit card frame-based auto mic mixing system featuring combine-separate function and programmable gain control (PGC) modules. Combine-separate functionality is useful for ballroom applications with movable partitions that permit portions or all of a room to be used for one program or multiple programs. PGC modules compensate individual mic channel gain for soft-spoken or loud presenters, by slightly boosting or cutting channel gain, respectively.{{cite video |url=https://www.youtube.com/watch?v=MCyLHvyqa4g&t=214 |title=Innovative Electronic Designs - Corporate Story}}

At the 87th AES Convention in 1989, Dugan introduced the idea of using an automixer inserted within target channels on a professional audio mixer. Each microphone's signal would be interrupted inside its channel strip and sent to a variable gain circuit contained within the automixer. The signal would then be returned to the mixer at a level consistent with the Dugan algorithm.{{cite journal|author=Dan Dugan |url=http://www.aes.org/e-lib/browse.cfm?elib=5859 |title=Application of Automatic Mixing Techniques to Audio Consoles |publisher=Audio Engineering Society |date=October 1989 |accessdate=2011-03-12}} This became the Dugan Model D automixer.[http://www.dandugan.com/Products/Model_D/D.brochure.html Dan Dugan Sound Design. Model D] {{webarchive |url=https://web.archive.org/web/20090829205856/http://www.dandugan.com/Products/Model_D/D.brochure.html |date=August 29, 2009 }}

In 1991, Dugan's patent expired. Competing manufacturers began to bring the Dugan algorithm directly to their product designs. In 1993, Travis M. Sims, Jr. of Lectrosonics (Rio Rancho, New Mexico) was granted a patent for a sound system with rate controlled, variable attenuation of microphone inputs, including the Dugan algorithm as well as loudspeaker zone attenuation when in close proximity to an active microphone.{{Cite patent|country=US|number=5204908|pubdate=1993-04-20|title=Sound system with rate controlled, variable attenuation|assign1=Lectrosonics Inc.|inventor1-last=Sims|inventor1-first=Travis M.}} The loudspeaker zone part of the patent cited a 1985 patent for proportional amplification by Eugene R. Griffith, Jr. of LVW Systems of Colorado Springs, a commercial audio contractor.{{Cite patent|country=US|number=4598418|pubdate=1986-07-01|title=Sound system employing automatic proportional amplification|inventor1-last=Griffith, Jr.|inventor1-first=Eugene R.|inventor2-last=Connett|inventor2-first=Steven T.}} In 1995, Sims and Lectrosonics gained another patent for an "Adaptive proportional gain audio mixing system" which incorporated a number of ideas including the Dugan algorithm for maintaining a constant total gain of all the inputs.{{Cite patent|country=US|number=5414776|pubdate=1995-05-09|title=Adaptive proportional gain audio mixing system|assign1=Lectrosonics Inc.|inventor1-last=Sims, Jr.|inventor1-first=Travis M.}}

In 1996, Dugan came out with the Model D-1, a speech-only economy model that did not offer the music capabilities of the Model D.

In 1997, John H. Roberts of Peavey Electronics was granted a patent for an automatic mixer priority circuit, enabling a hierarchy of logic weighting that allowed selected signals to push forward in the mix when they are in use, while still maintaining the useful constant unity, gain-sharing relationship first described by Dugan. The hierarchy enabled a host, moderator or chairperson to speak over other participants and retain control of the discussion.{{Cite patent|country=US|number=5652800|pubdate=1997-07-29|title=Automatic mixer priority circuit|assign1=Peavey Electronics Corp.|inventor1-last=Roberts|inventor1-first=John H.}} Peavey's Architectural Acoustics division used three levels of hierarchy in their 1998 "Automix 2" product, placing the first- and second-most influentially weighted sources at inputs 1 and 2, respectively.{{cite web |url=http://www.peavey.com/media/pdf/manuals/80304515.pdf |title=Automix 2 |format=PDF |accessdate=2011-03-12 |archive-url=https://web.archive.org/web/20110727121250/http://www.peavey.com/media/pdf/manuals/80304515.pdf |archive-date=July 27, 2011 |url-status=dead |df=mdy-all }}

Dan Dugan licensed his system to Protech Audio (Indian Lake, New York) in 1997, yielding the Protech 2000 model series.{{cite web|url=http://www.protechaudio.com/products/dugan.htm |title=Dugan Automixers – The World's Best Automixers |publisher=Protech Audio |accessdate=2011-03-12}}

In 2004, the first standard audio mixer incorporating an eight-channel automixer section was released by Peavey in their Sanctuary Series,[http://www.peavey.com/corp/innovation/index.cfm Peavey.com Peavey Innovations Timeline] {{webarchive |url=https://web.archive.org/web/20080914170131/http://www.peavey.com/corp/innovation/index.cfm |date=September 14, 2008 }} and in 2006 the similar HP-W was introduced by Crest.{{cite web|url=http://namm.harmony-central.com/SNAMM06/Content/CrestAudio/PR/HP-W-Console.html |title=Crest Audio Introduces The HP-W Professional Mixing Console |publisher=Harmony Central |date=July 15, 2006 |url-status=dead |archiveurl=https://web.archive.org/web/20080516034503/http://namm.harmony-central.com/SNAMM06/Content/CrestAudio/PR/HP-W-Console.html |archivedate=May 16, 2008 }} Both mixers were aimed at the house of worship market, adding functions that ease the process of audio mixing for religious organizations.

In 2007, Mark W. Gilbert and Gregory H. Canfield of Shure (Niles, Illinois) were granted a patent for a digital microphone automixer system that used time of arrival as its main decision-making criteria.{{cite patent|country=US|number=8644477|title=Digital Microphone Automixer|pubdate=2014-02-04|assign1=Shure Acquisition Holdings Inc.|inventor1-last=Gilbert|inventor1-first=Mark W.|inventor2-last=Canfield|inventor2-first=Gregory H.}}{{cite web |author=WIPO |url=https://patentscope.wipo.int/search/en/detail.jsf?docId=WO2007090010 |title=World Intellectual Property Organization. (WO/2007/090010) A DIGITAL MICROPHONE AUTOMIXER |publisher=Patentscope |accessdate=2025-05-21}}

File:Dugan automixers - D, D2-3, E-1, and Dugan-MY16.jpg automixers]]

In February 2011, Dugan announced an automixer card to plug in the accessory slot of a Yamaha digital mixing console such as the LS-9, M7CL or PM-5D. This card, the Dugan-MY16, can mix 16 channels of microphone inputs at 44.1–48 kHz or 8 channels at 88.2–96 kHz sampling rates. Channels to be automixed are assigned in the mixer's graphic user interface, and can then be controlled by a common web browser interface affecting only the Dugan-MY16 card, allowing remote control with an iPad, touchscreen computer or laptop over wireless network.{{cite web|url=http://expo.nabshow.com/mynabshow2011/public/Booth.aspx?IndexInList=405&FromPage=nz_ALProductSrch.aspx&BoothID=112275&Task=ProductsDetails&PRODID=3082&SortBy=productName1%20ASC |title=Dan Dugan Sound Design |publisher=National Association of Broadcasters |accessdate=March 21, 2011 |url-status=dead |archiveurl=https://web.archive.org/web/20120321162228/http://expo.nabshow.com/mynabshow2011/public/Booth.aspx?IndexInList=405&FromPage=nz_ALProductSrch.aspx&BoothID=112275&Task=ProductsDetails&PRODID=3082&SortBy=productName1%20ASC |archivedate=March 21, 2012 |df=mdy }}

• Speech intelligibility enhancement, James M. Kates of Signatron (1984). This system uses Dugan's automatic mixing algorithm to reconstitute several spectral regions of a signal divided into frequency bands for short-time spectral analysis to achieve greater intelligibility of spoken consonants.{{Cite patent|country=US|number=4454609|pubdate=1984-06-12|title=Speech intelligibility enhancement|assign1=Signatron Inc.|inventor1-last=Kates|inventor1-first=James M.}}
• Secure conferencing, patent by Raoul E. Drapeau (1993). An automixing algorithm attempts to mask incidental speech below the automix threshold but can be audible in the mix. The automix circuitry indicates which sources are active, and whether masking of low-level signals is occurring.{{Cite patent|country=US|number=5197098|pubdate=1993-03-23|title=Secure conferencing system|inventor1-last=Drapeau|inventor1-first=Raoul E.}}

• Electronic mixer
• Variable-gain amplifier

{{Reflist|}}

• {{cite magazine |url=http://svconline.com/microphones/products/avinstall_automatic_microphone_mixers/index.html |archive-url=https://web.archive.org/web/20110716171311/http://svconline.com/microphones/products/avinstall_automatic_microphone_mixers/index.html |archive-date=2011-07-16 |title=Technology Showcase: Automatic Microphone Mixers |date=May 2007 |magazine=Sound & Video Contractor |author=Bennett Liles}}

Category:Audio mixing

Category:Sound production technology