![Hornloudspeaker](https://upload.wikimedia.org/wikipedia/commons/a/aa/Hornloudspeaker.jpg)
A public address system (or PA system) is an electronic system comprising microphones, amplifiers, loudspeakers, and related equipment. It increases the apparent volume (loudness) of a human voice, musical instrument, or other acoustic sound source or recorded sound or music. PA systems are used in any public venue that requires that an announcer, performer, etc. be sufficiently audible at a distance or over a large area. Typical applications include sports stadiums, public transportation vehicles and facilities, and live or recorded music venues and events. A PA system may include multiple microphones or other sound sources, a mixing console to combine and modify multiple sources, and multiple amplifiers and loudspeakers for louder volume or wider distribution.
Simple PA systems are often used in small venues such as school auditoriums, churches, and small bars. PA systems with many speakers are widely used to make announcements in public, institutional and commercial buildings and locations—such as schools, stadiums, and passenger vessels and aircraft. Intercom systems, installed in many buildings, have both speakers throughout a building, and microphones in many rooms so occupants can respond to announcements. PA and Intercom systems are commonly used as part of an
emergency communication system An emergency communication system (ECS) is any system (typically computer-based) that is organized for the primary purpose of supporting one-way and two-way communication of emergency information between both individuals and groups of individuals. ...
.
The term ''
sound reinforcement system
A sound reinforcement system is the combination of microphones, signal processors, amplifiers, and loudspeakers in enclosures all controlled by a mixing console that makes live or pre-recorded sounds louder and may also distribute those sounds ...
'' generally means a PA system used specifically for live music or other performances.
In Britain any PA system is sometimes colloquially referred to as a
Tannoy
Tannoy is a British manufacturer of loudspeakers and public address systems. Founded by Guy Fountain in London in 1926 as the Tulsemere Manufacturing Company, today the company is part of the Music Tribe group of brands.
History
Tannoy Ltd is ...
, after the company of that name, now owned by TC Electronic Group, which supplied many of the PA systems used previously in Britain.
Early systems
Megaphone
![HPIM0145 megaphone](https://upload.wikimedia.org/wikipedia/commons/b/bd/HPIM0145_megaphone.jpg)
From the Ancient Greek era to the nineteenth century, before the invention of electric loudspeakers and amplifiers,
megaphone
A megaphone, speaking-trumpet, bullhorn, blowhorn, or loudhailer is usually a portable or hand-held, cone-shaped acoustic horn used to amplify a person's voice or other sounds and direct it in a given direction. The sound is introduced into ...
cones were used by people speaking to a large audience, to make their voice project more to a large space or group. Megaphones are typically portable, usually hand-held, cone-shaped
acoustic horn
An acoustic horn or waveguide is a tapered sound guide designed to provide an acoustic impedance match between a sound source and free air. This has the effect of maximizing the efficiency with which sound waves from the particular source are tran ...
s used to
amplify a person’s voice or other
sound
In physics, sound is a vibration that propagates as an acoustic wave, through a transmission medium such as a gas, liquid or solid.
In human physiology and psychology, sound is the ''reception'' of such waves and their ''perception'' by the ...
s and direct it towards a given direction. The sound is introduced into the narrow end of the megaphone, by holding it up to the face and speaking into it. The sound projects out the wide end of the cone. The user can direct the sound by pointing the wide end of the cone in a specific direction. In the 2020s,
cheerleading
Cheerleading is an activity in which the participants (called cheerleaders) cheer for their team as a form of encouragement. It can range from chanting slogans to intense physical activity. It can be performed to motivate sports teams, to ente ...
is one of the few fields where a nineteenth century-style cone is still used to project the voice. The device is also called “speaking-trumpet”, “bullhorn” or “loud hailer”.
Automatic Enunciator
In 1910, the
Automatic Electric Company
Automatic Electric Company (A.E. Co.) was an American telephone equipment supplier primarily for independent telephone companies in North America, but also had a worldwide presence. With its line of automatic telephone exchanges, it was also a lo ...
of Chicago, Illinois, already a major supplier of automatic telephone switchboards, announced it had developed a loudspeaker, which it marketed under the name of the ''Automatic Enunciator''. Company president Joseph Harris foresaw multiple potential uses, and the original publicity stressed the value of the invention as a hotel public address system, allowing people in all public rooms to hear announcements. In June 1910, an initial "semi-public" demonstration was given to newspaper reporters at the Automatic Electric Company building, where a speaker's voice was transmitted to loudspeakers placed in a dozen locations "all over the building".
A short time later, the Automatic Enunciator Company formed in Chicago order to market the new device, and a series of promotional installations followed.
[''Robert D. Fisher Manual of Valuable and Worthless Securities: Volume 6'' (1938), page 75.] In August 1912 a large outdoor installation was made at a water carnival held in Chicago by the Associated Yacht and Power Boat Clubs of America. Seventy-two loudspeakers were strung in pairs at forty-foot (12 meter) intervals along the docks, spanning a total of one-half mile (800 meters) of grandstands. The system was used to announce race reports and descriptions, carry a series of speeches about "The Chicago Plan", and provide music between races.
In 1913, multiple units were installed throughout the
Comiskey Park
Comiskey Park was a baseball park in Chicago, Illinois, located in the
Armour Square neighborhood on the near-southwest side of the city. The stadium served as the home of the Chicago White Sox of the American League from 1910 through 1990. Buil ...
baseball stadium in Chicago, both to make announcements and to provide musical interludes, with Charles A. Comiskey quoted as saying: "The day of the megaphone man has passed at our park." The company also set up an experimental service, called the
Musolaphone The Musolaphone (also marketed as the Multa Musola), developed by the Automatic Electric Company of Chicago, Illinois, was an audio distribution system that transmitted news and entertainment over telephone lines to subscribing homes and businesses. ...
, that was used to transmitted news and entertainment programming to home and business subscribers in south-side Chicago, but this effort was short-lived. The company continued to market the enunciators for making announcements in establishments such as hospitals, department stores, factories, and railroad stations, although the Automatic Enunciator Company was dissolved in 1926.
Magnavox
![Early vacuum tube public address system](https://upload.wikimedia.org/wikipedia/commons/6/64/Early_vacuum_tube_public_address_system.jpg)
Peter Jensen and Edwin Pridham of
Magnavox
Magnavox (Latin for "great voice", stylized as MAGNAVOX) is an American electronics company that since 1974 has been a subsidiary of the Dutch electronics corporation Philips.
The predecessor to Magnavox was founded in 1911 by Edwin Pridham and ...
began experimenting with sound reproduction in the 1910s. Working from a laboratory in
Napa, California
Napa is the largest city and county seat of Napa County and a principal city of Wine Country in Northern California. Located in the North Bay region of the Bay Area, the city had a population of 77,480 as of the end of 2021. Napa is a major t ...
, they filed the first patent for a
moving coil loudspeaker
A loudspeaker (commonly referred to as a speaker or speaker driver) is an electroacoustic transducer that converts an electrical audio signal into a corresponding sound. A ''speaker system'', also often simply referred to as a "speaker" or " ...
in 1911.
Four years later, in 1915, they built a dynamic loudspeaker with a
voice coil
A voice coil (consisting of a former, collar, and winding) is the coil of wire attached to the apex of a loudspeaker cone. It provides the motive force to the cone by the reaction of a magnetic field to the current passing through it. The te ...
, a corrugated
diaphragm and a
horn
Horn most often refers to:
*Horn (acoustic), a conical or bell shaped aperture used to guide sound
** Horn (instrument), collective name for tube-shaped wind musical instruments
*Horn (anatomy), a pointed, bony projection on the head of various ...
measuring with a aperture. The
electromagnet
An electromagnet is a type of magnet in which the magnetic field is produced by an electric current. Electromagnets usually consist of wire wound into a coil. A current through the wire creates a magnetic field which is concentrated in the ...
created a flux field of approximately 11,000
Gauss
Johann Carl Friedrich Gauss (; german: Gauß ; la, Carolus Fridericus Gauss; 30 April 177723 February 1855) was a German mathematician and physicist who made significant contributions to many fields in mathematics and science. Sometimes refer ...
.
Their first experiment used a
carbon microphone
The carbon microphone, also known as carbon button microphone, button microphone, or carbon transmitter, is a type of microphone, a transducer that converts sound to an electrical audio signal. It consists of two metal plates separated by granu ...
. When the 12 V battery was connected to the system, they experienced one of the first examples of
acoustic feedback
Audio feedback (also known as acoustic feedback, simply as feedback) is a positive feedback situation which may occur when an acoustic path exists between an audio input (for example, a microphone or guitar pickup) and an audio output (for exa ...
,
a typically unwanted effect often characterized by high-pitched sounds. They then placed the loudspeaker on the laboratory's roof, and claims say that the amplified human voice could be heard away.
Jensen and Pridham refined the system and connected a
phonograph
A phonograph, in its later forms also called a gramophone (as a trademark since 1887, as a generic name in the UK since 1910) or since the 1940s called a record player, or more recently a turntable, is a device for the mechanical and analogu ...
to the loudspeaker so it could broadcast recorded music.
They did this on a number of occasions, including once at the Napa laboratory, at the
Panama–Pacific International Exposition
The Panama–Pacific International Exposition was a world's fair held in San Francisco, California, United States, from February 20 to December 4, 1915. Its stated purpose was to celebrate the completion of the Panama Canal, but it was widely se ...
,
and on December 24, 1915 at
San Francisco City Hall
San Francisco City Hall is the seat of government for the City and County of San Francisco, California. Re-opened in 1915 in its open space area in the city's Civic Center, it is a Beaux-Arts monument to the City Beautiful movement that epitomi ...
alongside
Mayor
In many countries, a mayor is the highest-ranking official in a municipal government such as that of a city or a town. Worldwide, there is a wide variance in local laws and customs regarding the powers and responsibilities of a mayor as well a ...
James Rolph
James "Sunny Jim" Rolph Jr. (August 23, 1869 – June 2, 1934) was an American politician. A member of the Republican Party, he was elected to a single term as the 27th governor of California from January 6, 1931, until his death on June ...
.
This demonstration was official presentation of the working system, and approximately 100,000 people gathered to hear Christmas music and speeches "with absolute distinctness".
The first
outside broadcast
Outside broadcasting (OB) is the electronic field production (EFP) of television or radio programmes (typically to cover television news and sports television events) from a mobile remote broadcast television studio. Professional video camera ...
was made one week later, again supervised by Jensen and Pridham.
On December 30, when
Governor of California
The governor of California is the head of government of the U.S. state of California. The governor is the commander-in-chief of the California National Guard and the California State Guard.
Established in the Constitution of California, the g ...
Hiram Johnson
Hiram Warren Johnson (September 2, 1866August 6, 1945) was an American attorney and politician who served as the Governor of California, 23rd governor of California from 1911 to 1917. Johnson achieved national prominence in the early 20th century ...
was too ill to give a speech in person, loudspeakers were installed at the
Civic Auditorium in
San Francisco
San Francisco (; Spanish language, Spanish for "Francis of Assisi, Saint Francis"), officially the City and County of San Francisco, is the commercial, financial, and cultural center of Northern California. The city proper is the List of Ca ...
, connected to Johnson's house some miles away by cable and a microphone, from where he delivered his speech.
Jensen oversaw the governor using the microphone while Pridham operated the loudspeaker.
The following year, Jensen and Pridham applied for a patent for what they called their "Sound Magnifying Phonograph". Over the next two years they developed their first valve amplifier. In 1919 this was standardized as a 3-stage 25 watt amplifier.
This system was used by former US president
William Howard Taft
William Howard Taft (September 15, 1857March 8, 1930) was the 27th president of the United States (1909–1913) and the tenth chief justice of the United States (1921–1930), the only person to have held both offices. Taft was elected pr ...
at a speech in
Grant Park,
Chicago
(''City in a Garden''); I Will
, image_map =
, map_caption = Interactive Map of Chicago
, coordinates =
, coordinates_footnotes =
, subdivision_type = Country
, subdivision_name ...
, and first used by a current president when
Woodrow Wilson
Thomas Woodrow Wilson (December 28, 1856February 3, 1924) was an American politician and academic who served as the 28th president of the United States from 1913 to 1921. A member of the Democratic Party, Wilson served as the president of ...
addressed 50,000 people in
San Diego, California
San Diego ( , ; ) is a city on the Pacific Ocean coast of Southern California located immediately adjacent to the Mexico–United States border. With a 2020 population of 1,386,932, it is the eighth most populous city in the United States ...
.
Wilson's speech was part of his nationwide tour to promote the establishment of the
League of Nations
The League of Nations (french: link=no, Société des Nations ) was the first worldwide intergovernmental organisation whose principal mission was to maintain world peace. It was founded on 10 January 1920 by the Paris Peace Conference that ...
.
It was held on September 9, 1919 at
City Stadium. As with the San Francisco installation, Jensen supervised the microphone and Pridham the loudspeakers. Wilson spoke into two large horns mounted on his platform, which channelled his voice into the microphone.
Similar systems were used in the following years by
Warren G. Harding
Warren Gamaliel Harding (November 2, 1865 – August 2, 1923) was the 29th president of the United States, serving from 1921 until his death in 1923. A member of the Republican Party, he was one of the most popular sitting U.S. presidents. A ...
and
Franklin D. Roosevelt
Franklin Delano Roosevelt (; ; January 30, 1882April 12, 1945), often referred to by his initials FDR, was an American politician and attorney who served as the 32nd president of the United States from 1933 until his death in 1945. As the ...
.
Marconi
By the early 1920s,
Marconi had established a department dedicated to public address and began producing loudspeakers and amplifiers to match a growing demand.
In 1925,
George V
George V (George Frederick Ernest Albert; 3 June 1865 – 20 January 1936) was King of the United Kingdom and the British Dominions, and Emperor of India, from 6 May 1910 until Death and state funeral of George V, his death in 1936.
Born duri ...
used such a system at the
British Empire Exhibition
The British Empire Exhibition was a colonial exhibition held at Wembley Park, London England from 23 April to 1 November 1924 and from 9 May to 31 October 1925.
Background
In 1920 the British Government decided to site the British Empire Exhibit ...
, addressing 90,000 via six long-range loudspeakers.
This public use of loudspeakers brought attention to the possibilities of such technology. The 1925 Royal Air Force Pageant at
Hendon Aerodrome
Hendon Aerodrome was an aerodrome in London, England, that was an important centre for aviation from 1908 to 1968.
It was situated in Colindale, north west of Charing Cross. It nearly became a central hub of civil aviation ("the Charing Cros ...
used a Marconi system to allow the announcer to address the crowds, as well as amplify the band.
In 1929, the
Schneider Trophy
The Coupe d'Aviation Maritime Jacques Schneider, also known as the Schneider Trophy, Schneider Prize or (incorrectly) the Schneider Cup is a trophy that was awarded annually (and later, biennially) to the winner of a race for seaplanes and flying ...
race at
Calshot Spit
Calshot Spit is a one-mile long sand and slate, shingle bank, near the village of Calshot, located on the southern bank of the open end of Southampton Water, on the south coast of England.OS Explorer Map, New Forest, Scale: 1:25 000.Publisher: Or ...
used a public address system that had 200 horns, weighing a total of 20
ton
Ton is the name of any one of several units of measure. It has a long history and has acquired several meanings and uses.
Mainly it describes units of weight. Confusion can arise because ''ton'' can mean
* the long ton, which is 2,240 pounds
...
s.
Late 1920s–1930s
Engineers invented the first loud, powerful amplifier and speaker systems for public address systems and
movie theater
A movie theater (American English), cinema (British English), or cinema hall ( Indian English), also known as a movie house, picture house, the movies, the pictures, picture theater, the silver screen, the big screen, or simply theater is a ...
s. These large PA systems and movie theatre sound systems were very large and very expensive, and so they could not be used by most touring musicians. After 1927, smaller, portable AC mains-powered PA systems that could be plugged into a regular wall socket "quickly became popular with musicians"; indeed, "...
Leon McAuliffe
William Leon McAuliffe (January 3, 1917 – August 20, 1988) was an American Western swing guitarist who was a member of Bob Wills and His Texas Playboys during the 1930s. He was posthumously inducted into the Rock and Roll Hall of Fame as a me ...
(with
Bob Wills
James Robert Wills (March 6, 1905 – May 13, 1975) was an American Western swing musician, songwriter, and bandleader. Considered by music authorities as the founder of Western swing, he was known widely as the King of Western Swing (although S ...
) still used a carbon mic and a portable PA as late as 1935." During the late 1920s to mid-1930s, small portable PA systems and guitar combo amplifiers were fairly similar. These early amps had a "single volume control and one or two input jacks, field coil speakers" and thin wooden cabinets; remarkably, these early amps did not have tone controls or even an on-off switch.
Portable PA systems you could plug into wall sockets appeared in the early 1930s when the introduction of electrolytic capacitors and rectifier tubes enabled economical built-in power supplies that could plug into wall outlets. Previously, amplifiers required heavy multiple battery packs.
Electric megaphone
In the 1960s, an electric-amplified version of the megaphone, which used a loudspeaker, amplifier and a folded horn, largely replaced the basic cone-style megaphone. Small handheld, battery-powered electric megaphones are used by fire and rescue personnel, police, protesters, and people addressing outdoor audiences. With many small handheld models, the microphone is mounted at the back end of the device, and the user holds the megaphone in front of her/his mouth to use it, and presses a trigger to turn on the amplifier and loudspeaker. Larger electric megaphones may have a microphone attached by a cable, which enables a person to speak without having their face obscured by the flared horn.
Small systems
![Pa system](https://upload.wikimedia.org/wikipedia/commons/f/fa/Pa_system.jpg)
The simplest, smallest PA systems consist of a microphone, an amplifier, and one or more loudspeakers. PA systems of this type, often providing 50 to 200 watts of power, are often used in small venues such as school auditoriums, churches, and coffeehouse stages. Small PA systems may extend to an entire building, such as a restaurant, store, elementary school or office building. A sound source such as a
compact disc
The compact disc (CD) is a Digital media, digital optical disc data storage format that was co-developed by Philips and Sony to store and play digital audio recordings. In August 1982, the first compact disc was manufactured. It was then rele ...
player or radio may be connected to a PA system so that music can be played through the system. Smaller, battery-powered 12 volt systems may be installed in vehicles such as tour buses or school buses, so that the tour guide and/or driver can speak to all the passengers. Portable systems may be battery powered and/or powered by plugging the system into an electric wall socket. These may also be used for by people addressing smaller groups such as information sessions or team meetings. Battery-powered systems can be used by guides who are speaking to clients on walking tours.
Public address systems consist of input sources (microphones, sound playback devices, etc.),
amplifiers
An amplifier, electronic amplifier or (informally) amp is an electronic device that can increase the magnitude of a signal (a time-varying voltage or current). It may increase the power significantly, or its main effect may be to boost the v ...
, control and monitoring equipment (e.g., LED indicator lights, VU meters, headphones), and
loudspeakers
A loudspeaker (commonly referred to as a speaker or speaker driver) is an electroacoustic transducer that converts an electrical audio signal into a corresponding sound. A ''speaker system'', also often simply referred to as a "speaker" or "l ...
. Usual input include
microphone
A microphone, colloquially called a mic or mike (), is a transducer that converts sound into an electrical signal. Microphones are used in many applications such as telephones, hearing aids, public address systems for concert halls and public ...
s for speech or singing, direct inputs from musical instruments, and a recorded sound playback device. In non-performance applications, there may be a system that operators or automated equipment uses to select from a number of standard prerecorded messages. These input sources feed into preamplifiers and signal routers that direct the audio signal to selected zones of a facility (e.g., only to one section of a school). The preamplified signals then pass into the amplifiers. Depending on local practices, these amplifiers usually amplify the audio signals to 50 V, 70 V, or 100 V speaker line level. Control equipment monitors the amplifiers and speaker lines for faults before it reaches the loudspeakers. This control equipment is also used to separate zones in a PA system. The loudspeaker converts electrical signals into sound.
Large systems
![Public Address System rack 1](https://upload.wikimedia.org/wikipedia/commons/1/14/Public_Address_System_rack_1.jpg)
Some PA systems have speakers that cover more than one building, extending to an entire campus of a college, office or industrial site, or an entire outdoor complex (e.g., an athletic stadium). A large PA system may also be used as an
alert system during an emergency.
PA systems by size and subwoofer approach
Telephone paging systems
Some
private branch exchange
A business telephone system is a multiline telephone system typically used in business environments, encompassing systems ranging in technology from the key telephone system (KTS) to the private branch exchange (PBX).
A business telephone syst ...
(PBX) telephone systems use a paging facility that acts as a liaison between the telephone and a PA amplifier. In other systems, paging equipment is not built into the telephone system. Instead the system includes a separate paging controller connected to a trunk port of the telephone system. The paging controller is accessed as either a designated directory number or central office line. In many modern systems, the paging function is integrated into the telephone system, so the system can send announcements to the phone speakers.
Many retailers and offices choose to use the telephone system as the sole access point for the paging system, because the features are integrated. Many schools and other larger institutions are no longer using the large, bulky microphone PA systems and have switched to telephone system paging, as it can be accessed from many different points in the school.
PA over IP
''PA over IP'' refers to PA paging and
intercom
An intercom, also called an intercommunication device, intercommunicator, or interphone, is a stand-alone voice communications system for use within a building or small collection of buildings which functions independently of the public telephon ...
systems that use an Internet Protocol (IP) network, instead of a central amplifier, to distribute the audio signal to paging locations across a building or campus, or anywhere else in the reach of the IP network, including the Internet. Network-attached amplifiers and intercom units are used to provide the communication function. At the transmission end, a computer application transmits a digital audio stream via the local area network, using audio from the computer's
sound card
A sound card (also known as an audio card) is an internal expansion card that provides input and output of audio signals to and from a computer under the control of computer programs. The term ''sound card'' is also applied to external audio i ...
inputs or from stored audio recordings. At the receiving end, either specialized intercom modules (sometimes known as
IP speaker
A conventional loudspeaker is an electromechanical transducer that converts an electrical signal into sound. If locally powered, this can also be termed an active loudspeaker, meaning it contains an audio power amplifier that drives the loudspeake ...
s) receive these network transmissions and reproduce the analog audio signal. These are small, specialized network appliances addressable by an IP address, just like any other computer on the network.
WMT PA Systems
''Wireless Mobile Telephony (WMT) PA Systems'' refers to PA paging and
ntercomsystems that use any form of Wireless mobile telephony system such as GSM networks instead of a centralized amplifier to distribute the audio signal to paging locations across a building or campus, or other location. The GSM mobile Networks are used to provide the communication function. At the transmission end, a PSTN Telephone, mobile phone, VOIP phone or any other communication device that can access and make audio calls to a GSM based mobile SIM card can communicate with it. At the receiving end, a GSM transceiver receives these network transmissions and reproduce the analogue audio signal via a Power Amplifier and speaker. This was pioneered by Stephen Robert Pearson of Lancashire, England who was granted patents for the systems, which also incorporate control functionality. Using a WMT (GSM) network means that live announcements can be made to anywhere in the world where there is WMT connectivity. The patents cover all forms of WMT i.e., 2G, 3G, 4G ..... ××G. A UK company called Remvox Ltd (REMote VOice eXperience) has been appointed under license to develop and manufacture products based on the technology.
Long line PA
![Long Line Public Address Announcement](https://upload.wikimedia.org/wikipedia/commons/7/7e/Long_Line_Public_Address_Announcement.jpg)
A Long-Line Public Address (LLPA) system is any public address system with a distributed architecture, normally across a wide geographic area. Systems of this type are commonly found in the rail, light rail, and metro industries, and let announcements be triggered from one or several locations to the rest of the network over low bandwidth legacy copper, normally
PSTN
The public switched telephone network (PSTN) provides infrastructure and services for public telecommunication. The PSTN is the aggregate of the world's circuit-switched telephone networks that are operated by national, regional, or local teleph ...
lines using
DSL modems, or media such as
optical fiber
An optical fiber, or optical fibre in Commonwealth English, is a flexible, transparent fiber made by drawing glass (silica) or plastic to a diameter slightly thicker than that of a human hair. Optical fibers are used most often as a means to ...
, or
GSM-R
GSM-R, Global System for Mobile Communications – Railway or GSM-Railway is an international wireless communications standard for railway communication and applications.
A sub-system of European Rail Traffic Management System (ERTMS), it is us ...
, or IP-based networks.
Rail systems typically have an interface with a
passenger information system
A passenger information system, or passenger information display system, is an automated system for supplying users of public transport with information about the nature and the state of a public transport service through visual, voice or other m ...
(PIS) server, at each station. These are linked to train describers, which state the location of rolling stock on the network from sensors on trackside signaling equipment. The PIS invokes a stored message to play from a local or remote digital voice announcement system, or a series of message fragments to
assemble in the correct order, for example: " / the / 23.30 /
Great_Western_Railway
The Great Western Railway (GWR) was a British railway company that linked London with the southwest, west and West Midlands of England and most of Wales. It was founded in 1833, received its enabling Act of Parliament on 31 August 1835 and ran ...
/
Night_Riviera_sleeper_service / from /
London_Paddington
Paddington, also known as London Paddington, is a London station group, Central London railway terminus and London Underground station complex, located on Praed Street in the Paddington area. The site has been the London terminus of services pro ...
/ to /
Penzance
Penzance ( ; kw, Pennsans) is a town, civil parish and port in the Penwith district of Cornwall, United Kingdom. It is the most westerly major town in Cornwall and is about west-southwest of Plymouth and west-southwest of London. Situated ...
/ .... / will depart from platform / one / this train is formed of / 12_carriages /." Messages are routed via an IP network and are played on local amplification equipment. Taken together, the PA, routing, DVA, passenger displays and PIS interface are referred to as the ''customer information system (CIS)'', a term often used interchangeably with ''passenger information system''.
Small venue systems
Small clubs, bars and coffeehouses use a fairly simple set-up, with front of house speaker cabinets (and subwoofers, in some cases) aimed at the audience, and
monitor speaker cabinets aimed back at the performers so they can hear their vocals and instruments. In many cases,
front of house
In the performing arts, front of house (FOH) is the part of a performance venue that is open to the public. In theatres and live music venues, it consists of the auditorium and foyers, as opposed to the stage and backstage areas. In a theatre, t ...
speakers are elevated, either by mounting them on poles or by "flying" them from anchors in the ceiling. The Front of House speakers are elevated to prevent the sound from being absorbed by the first few rows of audience members. The subwoofers do not need to be elevated, because deep bass is omnidirectional. In the smallest
coffeehouse
A coffeehouse, coffee shop, or café is an establishment that primarily serves coffee of various types, notably espresso, latte, and cappuccino. Some coffeehouses may serve cold drinks, such as iced coffee and iced tea, as well as other non-ca ...
s and bars, the
audio mixer
Audio most commonly refers to sound, as it is transmitted in signal form. It may also refer to:
Sound
*Audio signal, an electrical representation of sound
*Audio frequency, a frequency in the audio spectrum
*Digital audio, representation of sound ...
may be onstage so that the performers can mix their own sound levels.
In larger bars, the audio mixer may be located in or behind the audience seating area, so that an audio engineer can listen to the mix and adjust the sound levels. The adjustments to the monitor speaker mix may be made by a single audio engineer using the main mixing board, or they may be made by a second audio engineer who uses a separate mixing board.
Large venue systems
For popular music concerts, a more powerful and more complicated PA System is used to provide
live sound reproduction
A sound reinforcement system is the combination of microphones, signal processors, amplifiers, and loudspeakers in enclosures all controlled by a mixing console that makes live or pre-recorded sounds louder and may also distribute those sounds ...
. In a concert setting, there are typically two complete PA systems: the "main" system and the "monitor" system. Each system consists of a mixing board, sound processing equipment, amplifiers, and speakers. The microphones that are used to pick up vocals and amplifier sounds are routed through both the main and monitor systems. Audio engineers can set different sound levels for each microphone on the main and monitor systems. For example, a
backup vocalist whose voice has a low sound level in the main mix may ask for a much louder sound level through their monitor speaker, so they can hear their singing.
* The "main" system (also known as ''
Front of House
In the performing arts, front of house (FOH) is the part of a performance venue that is open to the public. In theatres and live music venues, it consists of the auditorium and foyers, as opposed to the stage and backstage areas. In a theatre, t ...
'', commonly abbreviated FOH), which provides the amplified sound for the audience, typically uses a number of powerful amplifiers that drive a range of large, heavy-duty loudspeakers—including low-frequency speaker cabinets called subwoofers, full-range speaker cabinets, and high-range horns. A large club may use amplifiers to provide 3000 to 5000 watts of power to the "main" speakers. An outdoor concert may use 10,000 or more watts.
* The ''
monitor
Monitor or monitor may refer to:
Places
* Monitor, Alberta
* Monitor, Indiana, town in the United States
* Monitor, Kentucky
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* Monitor, Logan County, West ...
'' system reproduces the sounds of the performance and directs them towards the onstage performers (typically using wedge-shaped monitor speaker cabinets), to help them to hear the instruments and vocals. In British English, the monitor system is referred to as the "foldback". The monitor system in a large club may provide 500 to 1000 watts of power to several foldback speakers; at an outdoor concert, there may be several thousand watts of power going to the monitor system.
At a concert using live sound reproduction, sound engineers and technicians control the mixing boards for the "main" and "monitor" systems, adjusting tone, levels, and overall volume.
![Line Array and Subs](https://upload.wikimedia.org/wikipedia/commons/b/bc/Line_Array_and_Subs.jpg)
Touring productions travel with relocatable large
line-array PA systems, sometimes rented from an audio equipment hire company. The sound equipment moves from venue to venue along with various other equipment such as lighting and projection.
Acoustic feedback
All PA systems have the potential for
audio feedback
Audio feedback (also known as acoustic feedback, simply as feedback) is a positive feedback situation which may occur when an acoustic path exists between an audio input (for example, a microphone or guitar pickup) and an audio output (for examp ...
, which occurs when a microphone picks up sound from the speakers, which is re-amplified and sent through the speakers again. It often sounds like a loud high-pitched squeal or screech, and can occur when the volume of the system is turned up too high. Feedback only occurs when the
loop gain
In electronics and control system theory, loop gain is the sum of the gain, expressed as a ratio or in decibels, around a feedback loop. Feedback loops are widely used in electronics in amplifiers and oscillators, and more generally in both e ...
of the feedback loop is greater than one, so it can always be stopped by reducing the volume sufficiently.
Sound engineers take several steps to maximize
gain before feedback
In live sound mixing, gain before feedback (GBF) 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. In both fie ...
, including keeping microphones at a distance from speakers, ensuring that directional microphones are not pointed towards speakers, keeping the onstage volume levels down, and lowering gain levels at frequencies where the feedback is occurring, using a
graphic equalizer
Equalization, or simply EQ, in sound recording and reproduction is the process of adjusting the volume of different frequency bands within an audio signal. The circuit or equipment used to achieve this is called an equalizer.
Most hi-fi eq ...
, a
parametric equalizer
Equalization, or simply EQ, in sound recording and reproduction is the process of adjusting the volume of different frequency bands within an audio signal. The circuit or equipment used to achieve this is called an equalizer.
Most hi-fi eq ...
, or a
notch filter
In signal processing, a band-stop filter or band-rejection filter is a filter that passes most frequencies unaltered, but attenuates those in a specific range to very low levels. It is the opposite of a band-pass filter. A notch filter is a ...
. Some 2010s-era
mixing console
A mixing console or mixing desk is an electronic device for mixing audio signals, used in sound recording and reproduction and sound reinforcement systems. Inputs to the console include microphones, signals from electric or electronic inst ...
s and
effects unit
An effects unit or effects pedal is an electronic device that alters the sound of a musical instrument or other audio source through audio signal processing.
Common effects include distortion/overdrive, often used with electric guitar in el ...
s have automatic feedback preventing circuits.
Feedback prevention devices detect the start of unwanted feedback and use a precise notch filter to lower the gain of the frequencies that are feeding back. Some automated feedback detectors require the user to “set” the feedback-prone frequencies by purposely increasing gain (during a sound check) until some feedback starts to occur. This process is often referred to as "a ring out" or "an EQ" of a room/venue. The device then retains these frequencies in its memory and it stands by ready to cut them. Some automated feedback prevention devices can detect and reduce new frequencies other than those found in the sound check.
See also
*
Announcer
An announcer is a voice artist who relays information to the audience of a broadcast media programme or live event.
Television and other media
Some announcers work in television production, radio or filmmaking, usually providing narrations, ...
*
Instrument amplifier
An instrument amplifier is an electronic device that converts the often barely audible or purely electronic signal of a musical instrument into a larger electronic signal to feed to a loudspeaker. An instrument amplifier is used with musical ins ...
*
Intercom
An intercom, also called an intercommunication device, intercommunicator, or interphone, is a stand-alone voice communications system for use within a building or small collection of buildings which functions independently of the public telephon ...
*
1 Main Circuit
1 Main Circuit (1MC) is the term for the shipboard public address circuits on United States Navy and United States Coast Guard vessels. This provides a means of transmitting general information and orders to all internal ship spaces and topside ...
, the shipwide public address system on United States ships
References
External links
{{DEFAULTSORT:Public Address
Sound production technology
DJing
Address system
Audio engineering
Speech
Safety equipment