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 Voltage, also known as electric pressure, electric tension, or (electric) potential difference, is the difference in electric poten ...

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 distribution of audio or video content to a dispersed audience via any electronic mass communications medium, but typically one using the electromagnetic spectrum ( radio waves), in a one-to-many model. Broadcasting began ...

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 broa ...

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

multichannel television sound Multichannel Television Sound, better known as MTS, is the method of encoding three additional audio channels into an analog NTSC-format audio carrier. It was developed by the Broadcast Television Systems Committee, an industry group, and somet ...

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

NTSC The first American standard for analog television broadcast was developed by National Television System Committee (NTSC)National Television System Committee (1951–1953), Report and Reports of Panel No. 11, 11-A, 12–19, with Some supplement ...

) in 1984 in the United States. The NTSC

video format Video is an electronic medium for the recording, copying, playback, broadcasting, and display of moving visual media. Video was first developed for mechanical television systems, which were quickly replaced by cathode-ray tube (CRT) syste ...

and MTS are also used in

Canada Canada is a country in North America. Its ten provinces and three territories extend from the Atlantic Ocean to the Pacific Ocean and northward into the Arctic Ocean, covering over , making it the world's second-largest country by tot ...

and

Mexico Mexico (Spanish: México), officially the United Mexican States, is a country in the southern portion of North America. It is bordered to the north by the United States; to the south and west by the Pacific Ocean; to the southeast by Guatema ...

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 language family that evolved from colloquial Latin spoken on the Iberian peninsula. Today, it is a world language, global language with more than 500 millio ...

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 NOAA Weather Radio NWR; also known as NOAA Weather Radio All Hazards is an automated 24-hour network of VHF FM weather radio stations in the United States (U.S.) that broadcast weather information directly from a nearby National Weather Servi ...

services, or, particularly in the case of

PBS The Public Broadcasting Service (PBS) is an American public broadcasting, public broadcaster and Non-commercial activity, non-commercial, Terrestrial television, free-to-air television network based in Arlington, Virginia. PBS is a publicly fu ...

stations, a local

National Public Radio National Public Radio (NPR, stylized in all lowercase) is an American privately and state funded nonprofit media organization headquartered in Washington, D.C., with its NPR West headquarters in Culver City, California. It differs from other ...

(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 Audio description, also referred to as a video description, described video, or more precisely called a visual description, is a form of narration used to provide information surrounding key visual elements in a media work (such as a film or te ...

of programs for the

visually impaired Visual impairment, also known as vision impairment, is a medical definition primarily measured based on an individual's better eye visual acuity; in the absence of treatment such as correctable eyewear, assistive devices, and medical treatment� ...

. Under the

Twenty-First Century Communications and Video Accessibility Act of 2010 The Twenty-First Century Communications and Video Accessibility Act of 2010 (CVAA) is a United States accessibility law. Signed on October 8, 2010, by then-president Barack Obama, the bill amended the Communications Act of 1934 to include updated ...

, 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 national warning system in the United States designed to allow authorized officials to broadcast emergency alerts and warning messages to the public via cable, satellite, or broadcast television, and bot ...

and newscasts.

Frequencies

MTS features, including

stereo Stereophonic sound, or more commonly 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 configuration ...

and SAP, travel on subcarriers of the ''

video Video is an electronic medium for the recording, copying, playback, broadcasting, and display of moving visual media. Video was first developed for mechanical television systems, which were quickly replaced by cathode-ray tube (CRT) syste ...

'' 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 using frequency modulation (FM). Invented in 1933 by American engineer Edwin Armstrong, wide-band FM is used worldwide to provide high fidelity sound over broadcast radio. FM broadcasting is cap ...

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 The hertz (symbol: Hz) is the unit of frequency in the International System of Units (SI), equivalent to one event (or cycle) per second. The hertz is an SI derived unit whose expression in terms of SI base units is s−1, meaning that on ...

, 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 communication ...

. In turn, the MTS pilot is locked to the

horizontal sync Horizontal scan rate, or horizontal frequency, usually expressed in kilohertz, is the number of times per second that a raster-scan video system transmits or displays a complete horizontal line, as opposed to vertical scan rate, the number of times ...

frequency Frequency is the number of occurrences of a repeating event per unit of time. It is also occasionally referred to as ''temporal frequency'' for clarity, and is distinct from ''angular frequency''. Frequency is measured in hertz (Hz) which is eq ...

of the video carrier for stability. The SAP channel contains

mono Mono may refer to: Common meanings * Infectious mononucleosis, "the kissing disease" * Monaural, monophonic sound reproduction, often shortened to mono * Mono-, a numerical prefix representing anything single Music Performers * Mono (Japanese b ...

audio which has been dbx-

encode The Encyclopedia of DNA Elements (ENCODE) is a public research project which aims to identify functional elements in the human genome. ENCODE also supports further biomedical research by "generating community resources of genomics data, software ...

d for noise reduction, 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 the noise power, often expressed in deci ...

. The SAP audio has a

bandpass A band-pass filter or bandpass filter (BPF) is a device that passes frequencies within a certain range and rejects (attenuates) frequencies outside that range. Description In electronics and signal processing, a filter is usually a two-po ...

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 a 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 can also broadcast a "PRO" (

professional A professional is a member of a profession or any person who works in a specified professional activity. The term also describes the standards of education and training that prepare members of the profession with the particular knowledge and skil ...

) audio subcarrier which is used to communicate with station personnel, particularly those engaged in

electronic news gathering Electronic news-gathering (ENG) or electronic journalism (EJ) is usage of electronic video and audio technologies by reporters to gather and present news instead of using film cameras. The term was coined during the rise of videotape techno ...

. 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 reporters and

cameramen A camera operator, or depending on the context cameraman or camerawoman, is a professional operator of a film camera or video camera as part of a film crew. The term "cameraman" does not imply that a male is performing the task. In filmmakin ...

. 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 Television receive-only (TVRO) is a term used chiefly in North America, South America to refer to the reception of satellite television from FSS-type satellites, generally on C-band analog; free-to-air and unconnected to a commercial DBS prov ...

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. The signals are received via an outdoor parabolic antenna comm ...

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, a g ...

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

Morse code Morse code is a method used in telecommunication to encode text characters as standardized sequences of two different signal durations, called ''dots'' and ''dashes'', or ''dits'' and ''dahs''. Morse code is named after Samuel Morse, one of ...

. On FM radio,

radio reading service A radio reading service or reading service for the blind is a public service of many universities, community groups and public radio stations, where a narrator reads books, newspapers and magazines aloud for the benefit of the blind and vision-imp ...

s 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 an in-band on-channel (IBOC) digital radio broadcast technology. It generally simulcasts an existing analog radio station in digital format with less noise and with additional text information. HD Radio is used ...

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 encoding, in contrast to the earlier analog television technology which used analog signals. At the time of its development it was considered an innovative adva ...

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 subchannel In broadcasting, digital subchannels are a method of transmitting more than one independent program stream simultaneously from the same digital radio or television station on the same radio frequency channel. This is done by using data compress ...

s 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