Second audio program (SAP), also known as secondary audio programming, is an auxiliary

audio channel An audio signal is a representation of sound, typically using either a changing level of electrical voltage for analog signals or a series of binary numbers for digital signals. Audio signals have frequencies in the audio frequency range of ro ...

for

analog television Analog television is the original television technology that uses analog signals to transmit video and audio. In an analog television broadcast, the brightness, colors and sound are represented by amplitude, instantaneous phase and frequency, ...

that can be

broadcast Broadcasting is the data distribution, distribution of sound, audio audiovisual content to dispersed audiences via a electronic medium (communication), mass communications medium, typically one using the electromagnetic spectrum (radio waves), ...

or transmitted both over-the-air and by

cable television Cable television is a system of delivering television programming to consumers via radio frequency (RF) signals transmitted through coaxial cables, or in more recent systems, light pulses through fibre-optic cables. This contrasts with bro ...

. Used mostly for audio description or other languages, SAP is part of the

multichannel television sound Multichannel Television Sound (MTS) is the method of encoding three additional audio channels into analog 4.5 MHz audio carriers on System M and System N.The system was developed by an industry group known as the Broadcast Television Systems ...

(MTS) standard originally set by the National Television Systems Committee (

NTSC NTSC (from National Television System Committee) is the first American standard for analog television, published and adopted in 1941. In 1961, it was assigned the designation System M. It is also known as EIA standard 170. In 1953, a second ...

) in 1984 in the United States. The NTSC video format and MTS are also used in

Canada Canada is a country in North America. Its Provinces and territories of Canada, ten provinces and three territories extend from the Atlantic Ocean to the Pacific Ocean and northward into the Arctic Ocean, making it the world's List of coun ...

and

Mexico Mexico, officially the United Mexican States, is a country in North America. It is the northernmost country in Latin America, and borders the United States to the north, and Guatemala and Belize to the southeast; while having maritime boundar ...

Usage

SAP is often used to provide audio tracks in languages other than the native language included in the program. In the United States, this is sometimes used for

Spanish-language Spanish () or Castilian () is a Romance languages, Romance language of the Indo-European languages, Indo-European language family that evolved from the Vulgar Latin spoken on the Iberian Peninsula of Europe. Today, it is a world language, gl ...

audio (especially during sports telecasts), often leading to the function being referred to facetiously as the "Spanish audio program". Likewise, some Spanish-language programs may, in rare cases, offer English on SAP. Some stations may relay NOAA Weather Radio services, or, particularly in the case of PBS stations, a local

National Public Radio National Public Radio (NPR) is an American public broadcasting organization headquartered in Washington, D.C., with its NPR West headquarters in Culver City, California. It serves as a national Radio syndication, syndicator to a network of more ...

(NPR) sister station, on the audio channel when SAP is not being used. In Canada, parliamentary and public affairs channel CPAC similarly uses SAP to carry both English and French-language audio. SAP is also a means of distribution for audio description of programs for the visually impaired. Under the Twenty-First Century Communications and Video Accessibility Act of 2010, top U.S. television networks and cable networks have been gradually required to broadcast quotas of audio described programming per-quarter, Since May 26, 2015, broadcasters have been required under the Act to provide dictations on SAP of any "emergency information" displayed in a textual format outside of the

Emergency Alert System The Emergency Alert System (EAS) is a Emergency population warning, national warning system in the United States designed to allow authorized officials to broadcast emergency alerts and warning messages to the public via Cable television, cable ...

and newscasts.

Frequencies

MTS features, including

stereo Stereophonic sound, commonly shortened to stereo, is a method of sound reproduction that recreates a multi-directional, 3-dimensional audible perspective. This is usually achieved by using two independent audio channels through a configurat ...

and SAP, travel on subcarriers of the ''

video Video is an Electronics, electronic medium for the recording, copying, playback, broadcasting, and display of moving picture, moving image, visual Media (communication), media. Video was first developed for mechanical television systems, whi ...

'' carrier, much like color for television. It is ''not'' carried on the audio carrier in the manner of stereo sound for an

FM radio FM broadcasting is a method of radio broadcasting that uses frequency modulation (FM) of the radio broadcast carrier wave. Invented in 1933 by American engineer Edwin Armstrong, wide-band FM is used worldwide to transmit high fidelity, high-f ...

broadcast, however, as it only has a

frequency deviation Frequency deviation (f_) is used in FM radio to describe the difference between the minimum or maximum extent of a frequency modulated signal, and the nominal center or carrier frequency. The term is sometimes mistakenly used as synonymous with fre ...

of ±25 kHz, whereas regular FM broadcasting has a deviation of ±75 kHz. The SAP subcarrier is located at 78.670 kHz, which is five times the 15.734 kHz corresponding to the MTS

pilot signal In telecommunications, a pilot signal is a signal, usually a single frequency, transmitted over a communications system for supervisory, control, equalization, continuity, synchronization, or reference purposes. Uses in different communicat ...

. In turn, the MTS pilot is locked to the horizontal sync

frequency Frequency is the number of occurrences of a repeating event per unit of time. Frequency is an important parameter used in science and engineering to specify the rate of oscillatory and vibratory phenomena, such as mechanical vibrations, audio ...

of the video carrier for stability. The SAP channel contains mono audio which has been

dbx dbx or DBX may refer to: * dbx (debugger), a Unix source-level debugger * dbx (company), a professional audio recording equipment company ** dbx (noise reduction), a noise reduction system invented by dbx, Inc. * .dbx, the file extension for Micros ...

- encoded for

noise reduction Noise reduction is the process of removing noise from a signal. Noise reduction techniques exist for audio and images. Noise reduction algorithms may distort the signal to some degree. Noise rejection is the ability of a circuit to isolate an u ...

, to improve the

signal-to-noise ratio Signal-to-noise ratio (SNR or S/N) is a measure used in science and engineering that compares the level of a desired signal to the level of background noise. SNR is defined as the ratio of signal power to noise power, often expressed in deci ...

. The SAP audio has a bandpass from 60 Hz to 12 kHz, which is less than the "regular" audio channel which runs from 50 Hz to 15 kHz. Though not technically an SAP channel,

television station A television station is a set of equipment managed by a business, organisation or other entity such as an amateur television (ATV) operator, that transmits video content and audio content via radio waves directly from a transmitter on the earth's s ...

s can also broadcast a "PRO" (

professional A professional is a member of a profession or any person who work (human activity), works in a specified professional activity. The term also describes the standards of education and training that prepare members of the profession with the partic ...

) audio subcarrier which is used to communicate with station personnel, particularly those engaged in electronic news gathering. This one-way audio channel allows individuals at the television station to send messages to people located away from the station, and is frequently employed during on-location newscasts as the foldback channel to

reporter A journalist is a person who gathers information in the form of text, audio or pictures, processes it into a newsworthy form and disseminates it to the public. This is called journalism. Roles Journalists can work in broadcast, print, advertis ...

s and cameramen. This channel is located at 6.5 times the pilot (102.271 kHz), and is also part of the MTS standard.

Other media

Second audio programs are also available in other media. On analog television receive-only

satellite television Satellite television is a service that delivers television programming to viewers by relaying it from a communications satellite orbiting the Earth directly to the viewer's location.ITU Radio Regulations, Section IV. Radio Stations and Systems ...

systems, audio programs are manually tuned by their subcarrier frequency, commonly around 6 MHz, often as low as 5.8 or as high as 7.2. These travel the same way as the

discrete Discrete may refer to: *Discrete particle or quantum in physics, for example in quantum theory * Discrete device, an electronic component with just one circuit element, either passive or active, other than an integrated circuit * Discrete group, ...

left and right main audio channels, and ATIS station ID, which is heard as

Morse code Morse code is a telecommunications method which Character encoding, encodes Written language, text characters as standardized sequences of two different signal durations, called ''dots'' and ''dashes'', or ''dits'' and ''dahs''. Morse code i ...

. On FM radio, radio reading services and other audio programs can be heard on subcarriers through subsidiary communications authority; however, these are generally prohibited from public listening without special equipment.

HD Radio HD Radio (HDR) is a trademark for in-band on-channel (IBOC) digital radio broadcast technology. HD radio generally simulcast, simulcasts an existing analog radio station in digital format with less noise and with additional text information. HD R ...

subchannels, somewhat more widely available, operate on a similar premise but generally carry totally unrelated programming to the main feed. On

digital television Digital television (DTV) is the transmission of television signals using Digital signal, digital encoding, in contrast to the earlier analog television technology which used analog signals. At the time of its development it was considered an ...

systems, selection is done through a menu as with analog television, though some provide easier access rather than having to dig down to find the option. Stations may also choose to transmit audio-only programs by assigning them to separate digital subchannels with an optional screen of title and artist information; however, this prevents the viewer from watching the main video in the case of television stations.

References

{{DEFAULTSORT:Second Audio Program Broadcast engineering Television technology Broadcasting