Automixer
Encyclopedia
Live sound mixing
Live sound mixing is the art of combining and processing a number of audio signals together to create a "mix" that the audience or performers at a live show hear. There can be a variety of different mixes required, depending on the performance requirements...
device that automatically attenuates the strength of a microphone
Microphone
A microphone is an acoustic-to-electric transducer or sensor that converts sound into an electrical signal. In 1877, Emile Berliner invented the first microphone used as a telephone voice transmitter...
's audio signal
Audio signal
An audio signal is an analog representation of sound, typically as an electrical voltage. Audio signals may be synthesized directly, or may originate at a transducer such as a microphone, musical instrument pickup, phonograph cartridge, or tape head. Loudspeakers or headphones convert an electrical...
when it is not being used. Automixers reduce the hiss, rumble, reverberation
Reverberation
Reverberation is the persistence of sound in a particular space after the original sound is removed. A reverberation, or reverb, is created when a sound is produced in an enclosed space causing a large number of echoes to build up and then slowly decay as the sound is absorbed by the walls and air...
and noise that occur when several microphones operate simultaneously. They may also be used to mix sound sources other than microphones.
Automixers are typically used to mix panel discussions on television talk show
Talk show
A talk show or chat show is a television program or radio program where one person discuss various topics put forth by a talk show host....
s and at conferences and seminars. They can also be used to mix actors' wireless microphones in theater productions and musicals. Automixers are frequently employed in settings where it is expected that a live sound operator
Sound operator
The sound operator is the person responsible for the overall and total execution of all sound-related aspects of a theatrical performance...
will be not present, such as courtrooms and city council chambers.
Automixer hardware or software uses a variety of methods that allow increased gain before feedback
Gain before feedback
In live sound mixing, gain before feedback is a practical measure of how much a microphone can be amplified in a sound reinforcement system before causing audio feedback. In audiology, GBF is a measure of hearing aid performance...
for live sound reinforcement as well as reducing comb filter
Comb filter
In signal processing, a comb filter adds a delayed version of a signal to itself, causing constructive and destructive interference. The frequency response of a comb filter consists of a series of regularly spaced spikes, giving the appearance of a comb....
ing between multiple microphones for recorded and broadcast
Broadcast
Broadcast or Broadcasting may refer to:* Broadcasting, the transmission of audio and video signals* Broadcast, an individual television program or radio program* Broadcast , an English electronic music band...
applications.
Use
Automixers balance multiple sound sources based on each source's level, quickly and dramatically adjusting the various signal levels automatically. Automixers are used in live sound reinforcement to maintain a steady limit on the overall signal level of the microphones; if a public addressPublic address
A public address system is an electronic amplification system with a mixer, amplifier and loudspeakers, used to reinforce a sound source, e.g., a person giving a speech, a DJ playing prerecorded music, and distributing the sound throughout a venue or building.Simple PA systems are often used in...
system is set up so that one microphone will not feed back
Audio feedback
Audio feedback is a special kind of positive feedback which occurs when a sound loop exists between an audio input and an audio output...
, then, in general, multiple microphones will not feed back if they are automixed. The equivalent number of open mics (NOM) present at the output of the automixer is kept low, regardless of the actual number of open mics.
While a skilled audio mix operator can greatly enhance the performance of a sound reinforcement system
Sound reinforcement system
A sound reinforcement system is the combination of microphones, signal processors, amplifiers, and loudspeakers that makes live or pre-recorded sounds louder and may also distribute those sounds to a larger or more distant audience...
he 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) because the operator does not respond quickly enough to "fade up" an audio signal. A properly adjusted automixer can prevent losing words or phrases due to upcut mistakes or lapses of attention.
History
Frank J. Clement and Bell LabsBell Labs
Bell Laboratories is the research and development subsidiary of the French-owned Alcatel-Lucent and previously of the American Telephone & Telegraph Company , half-owned through its Western Electric manufacturing subsidiary.Bell Laboratories operates its...
received a patent in 1969 for a multiple station conference telephone system that switched its output to the loudest input. 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.
Some systems using electro-mechanical switching in regard to 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. 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.
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 ambience. It was intended for speakerphone conferencing applications. In 1972, Keith A. T. Knox with the British Post Office Corporation
General Post Office
General Post Office is the name of the British postal system from 1660 until 1969.General Post Office may also refer to:* General Post Office, Perth* General Post Office, Sydney* General Post Office, Melbourne* General Post Office, Brisbane...
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.
Dan Dugan
Dan Dugan (audio engineer)
Dan Dugan is an American audio engineer, inventor, and nature sounds recordist. He was the first person to be called a sound designer, and he developed the first effective automatic microphone mixer: the automixer.-Early career:...
showed his first "Adaptive Threshold Automatic Microphone Mixing System" in 1974 at the 49th Audio Engineering Society
Audio Engineering Society
Established in 1948, the Audio Engineering Society draws its membership from amongst engineers, scientists, other individuals with an interest or involvement in the professional audio industry. The membership largely comprises engineers developing devices or products for audio, and persons working...
(AES) meeting in New York, 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 individual level. In 1976, Dugan was granted a patent for an automatic microphone mixing process whereby the total gain of the system remains constant. 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
Harvey Fletcher
Harvey Fletcher was an American physicist. Known as the "father of stereophonic sound" he is credited with the invention of the audiometer and hearing aid...
. The algorithm was elegantly simple: 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. Dugan licensed the system to Altec who released several automixer models including the 1674A, -B and -C series and the 1684A, all focusing on speech applications. (The 1684A became an Electrovoice product and is currently administered by their Commercial division.) 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". IRP released the Voice-Matic series of 4x1 and 8x1 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. This master output reduction was the solution used by Yamaha Pro Audio
Yamaha Pro Audio
Yamaha Pro Audio, Inc. is a company that offers a complete line of professional audio products for the live sound and sound reinforcement markets...
two decades later in their DME series of digital signal processing
Digital signal processing
Digital signal processing is concerned with the representation of discrete time signals by a sequence of numbers or symbols and the processing of these signals. Digital signal processing and analog signal processing are subfields of signal processing...
(DSP) products, incorporating an automixer function which was otherwise an 8- or 16-channel noise gate.
Eugene Campbell and Terrance Whittemore of Colorado
Colorado
Colorado is a U.S. state that encompasses much of the Rocky Mountains as well as the northeastern portion of the Colorado Plateau and the western edge of the Great Plains...
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.
Shure
Shure Incorporated is an American corporation originally founded by Sidney N. Shure in Chicago, Illinois in 1925 as a supplier of radio parts kits. The company became a consumer and professional audio-electronics manufacturer of microphones, wireless microphone systems, phonograph cartridges,...
(Evanston, Illinois
Evanston, Illinois
Evanston is a suburban municipality in Cook County, Illinois 12 miles north of downtown Chicago, bordering Chicago to the south, Skokie to the west, and Wilmette to the north, with an estimated population of 74,360 as of 2003. It is one of the North Shore communities that adjoin Lake Michigan...
) 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. 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.
At the 87th AES Convention in 1989, Dugan introduced the idea of using an automixer inserted
Insert (effects processing)
In audio processing and sound reinforcement, an insert is an access point built into the mixing console, allowing the user to add external line level devices into the signal flow between the microphone preamplifier and the mix bus....
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. This became the Dugan Model D automixer.
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
Rio Rancho, New Mexico
There were 18,995 households out of which 40.3% had children under the age of 18 living with them, 59.4% were married couples living together, 10.3% had a female householder with no husband present, and 25.7% were non-families. 20.8% of all households were made up of individuals and 7.9% had...
) 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. 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
Colorado Springs, Colorado
Colorado Springs is a Home Rule Municipality that is the county seat and most populous city of El Paso County, Colorado, United States. Colorado Springs is located in South-Central Colorado, in the southern portion of the state. It is situated on Fountain Creek and is located south of the Colorado...
, a commercial audio contractor. 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.
In 1996, Dugan came out with the Model D-1, a speech-only economy model that did not offer the music system of the Model D.
In 1997, John H. Roberts of Peavey Electronics
Peavey Electronics
Peavey Electronics Corporation is one of the largest audio equipment manufacturers in the world, headquartered in Meridian, Mississippi in the United States.- History :...
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. 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.
Dan Dugan licensed his system to Protech Audio (Indian Lake, New York
Indian Lake, New York
Indian Lake is a town in Hamilton County, New York, United States. The population was 1,471 at the 2000 census. The name is from a large lake partly inside the town.The Town of Indian Lake is on the east border of the county and is northeast of Utica....
) in 1997, yielding the Protech 2000 model series.
In 2004, the first standard audio mixer incorporating an eight-channel automixer section was released by Peavey in their Sanctuary Series, and in 2006 the similar HP-W was introduced by Crest. Both mixers were aimed at the House of Worship
Place of worship
A place of worship or house of worship is an establishment or her location where a group of people comes to perform acts of religious study, honor, or devotion. The form and function of religious architecture has evolved over thousands of years for both changing beliefs and architectural style...
market, adding functions that ease the process of audio mixing to religious organizations.
In 2007, Mark W. Gilbert and Gregory H. Canfield of Shure (Niles, Illinois
Niles, Illinois
Niles is a village in Maine and Niles Townships, Cook County, Illinois, United States. The 2010 population from the U.S. Census Bureau is 29,803.The current mayor of Niles is Robert M. Callero.-History:Niles was first settled in 1827....
) were granted a patent for a digital microphone automixer system that used time of arrival as its main decision-making criteria.
In February 2011, Dugan announced an automixer card to plug in the accessory slot of a Yamaha digital mixing console
Digital mixing console
In professional audio, a Digital Mixing Console , is an electronic device for combining, routing, and changing the dynamics of digital audio samples. The digital audio samples are summed to produce a combined output. A professional digital mixing console is a dedicated desk or control surface...
such as the LS-9, M7CL
M7CL
The Yamaha M7CL is a digital mixer manufactured by Yamaha Pro Audio. Two models with onboard analog input currently exist: the M7CL-32 and M7CL-48. These models have 40 - and 56 -input channels respectively, counting mono channels...
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
IPad
The iPad is a line of tablet computers designed, developed and marketed by Apple Inc., primarily as a platform for audio-visual media including books, periodicals, movies, music, games, and web content. The iPad was introduced on January 27, 2010 by Apple's then-CEO Steve Jobs. Its size and...
, touchscreen computer or laptop over wireless network.
Related applications
- 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 that has been divided into frequency bands for short-time spectral analysis in order to achieve greater intelligibility of spoken consonants.
- Secure conferencing, patent by Raoul E. Drapeau (1993). An automixing algorithm attempts to mask incidental speech that is below automix threshold but which can be audible in the mix. The automix circuitry indicates which sources are active, and whether masking of low-level signals is occurring.
Automixer manufacturers and products
- AKG AcousticsAKG AcousticsAKG Acoustics is an Austrian manufacturer of microphones, headphones, wireless audio systems and related accessories for professional and consumer markets...
; AS8 - APB Dynasonics; ProSpec Auto-Mixer
- Audio-TechnicaAudio-Technica, established in 1962 and headquartered in Tokyo, Japan, is a company that designs and manufactures professional wired and wireless microphones, headphones, phonographic magnetic cartridges, and other audio equipment. One of their most famous products was a battery-operated, portable record player...
a; AT-MX341a SmartMixer. - beyerdynamicBeyerdynamicBeyerdynamic GmbH & Co. KG is a German audio equipment manufacturer, which produces microphones, headphones, wireless audio systems and conference systems. Beyerdynamic remains a family owned company since it was founded in 1924.-History:...
; MCS 100 - Biamp SystemsBiamp SystemsBiamp Systems is a manufacturer of commercial audio electronics based in Beaverton, Oregon. Founded in 1976, Biamp has a long history of producing analog mixers, equalizers, and amplifiers. Since the early 2000's, their new products have mainly consisted of programmable audio DSP's....
; Audia, Nexia, and AutoTwo - Crest AudioCrest AudioCrest Audio, Inc is an American company that produces professional sound equipment, including audio mixers, power amplifiers, and loudspeakers. Crest Audio was founded in the late 1970s by Jean-Pierre Prideaux in California...
; HP-W - Crown; USM-810
- Gentner, Comrex, ClearOne; Converge Series, XAP Series
- Dan Dugan Sound Design; Models A, D, D-1, D-2, D-3, E and E-1
- Industrial Research Products; Voice-Tech
- Intelix; AMIX Series
- Ivie; AudioNet Automatic Matrix Mixers
- Lectrosonics; LecNet2 Series
- Peavey ElectronicsPeavey ElectronicsPeavey Electronics Corporation is one of the largest audio equipment manufacturers in the world, headquartered in Meridian, Mississippi in the United States.- History :...
; Sanctuary, Mediamatrix, NION, Automix 4, Automix 2, etc. - RaneRane Corp.Rane Corporation is a pro audio equipment manufacturer. Located in Mukilteo, Washington, it was made up of former employees of Phase Linear Corporation, and started out with products aimed at small live bands...
; RPM 88 - ShureShureShure Incorporated is an American corporation originally founded by Sidney N. Shure in Chicago, Illinois in 1925 as a supplier of radio parts kits. The company became a consumer and professional audio-electronics manufacturer of microphones, wireless microphone systems, phonograph cartridges,...
; SCM410, SCM810, FP410 - SymetrixSymetrixSymetrix is a manufacturer of professional audio signal processing products based in Mountlake Terrace, Washington, USA.The company was founded in Seattle, WA in 1976 by Dane Butcher who was at that time working as a recording engineer. Symetrix currently specializes in audio DSP hardware and...
; SymNet Automixing - TOATOA Corp.TOA Corporation can be confused with TOA Construction Corporation, which also is known as TOA Corporation or Thai based TOA Paint.The or TOA Electric Corporation is a Japanese electronics company. They started operating in 1934 in Kobe, Japan, and were incorporated in 1949...
; AX-1000A, 9000 Series Digital Matrix Mixer/Amplifier - Yamaha Pro AudioYamaha Pro AudioYamaha Pro Audio, Inc. is a company that offers a complete line of professional audio products for the live sound and sound reinforcement markets...
; Dugan-MY16 card, for the accessory slot of the LS-9, M7CL, or PM-5D