engineering

Second audio program

Second audio program is a engineering topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Second audio program rather than just read about it. In short: Second audio program (SAP), also known as secondary audio programming, is an auxiliary audio channel for analog television that can be broadcast or transmitted both over-the-air and by cable television. Used mostly for audio description or other languages, SAP is part of the multichannel television sound (MTS) standard originally set by the National Television System Committee (NTSC) in 1984 in the United States.

Key takeaways

Second audio program belongs to engineering; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Second audio program to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Second audio program from memory before moving on to harder problems.

Reference excerpt

Second audio program (SAP), also known as secondary audio programming, is an auxiliary audio channel for analog television that can be broadcast or transmitted both over-the-air and by cable television. Used mostly for audio description or other languages, SAP is part of the multichannel television sound (MTS) standard originally set by the National Television System Committee (NTSC) in 1984 in the United States. The NTSC video format and MTS are also used in Canada and Mexico.

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 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 offer English on SAP, seen with soccer networks including beIN Sports (which features the same setup on its English and Spanish channels, and more rarely with general channels. Some stations may relay NOAA Weather Radio services, or, particularly in the case of PBS stations, a local National Public Radio (NPR) sister station, on the audio channel when SAP is not being used, and even commercial radio stations which are either sister operations or broker their programming onto the SAP channel. 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 and newscasts.

Frequencies MTS features, including stereo and SAP, travel on subcarriers of the video carrier, much like color for television. It is not carried on the audio carrier in the manner of stereo sound for an FM radio broadcast, however, as it only has a frequency deviation of ±25 kHz, whereas regular FM broadcasting has a deviation of ±75 kHz. T MTS pilot is locked to the horizontal sync frequency of the video carrier for stability. The SAP channel contains mono audio which has been dbx-encoded for noise reduction, to improve the signal-to-noise ratio. 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 stations can also broadcast a "PRO" (professional) 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 reporters 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 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 left and right main audio channels, and ATIS station ID, which is heard as Morse code. 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 subchannels, somewhat more widely available, operate on a similar premise but generally carry totally unrelated programming to the main feed. On digital television 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

Worked examples

Example 1 — a first encounter with Second audio program

Start with the simplest possible case. Write down what Second audio program claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In engineering, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Second audio program before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Second audio program ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Second audio program

In research: Second audio program appears in engineering research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Second audio program in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Second audio program is common in secondary-school and first-year university syllabi. It links to neighbouring topics Broadcast engineering, Broadcasting, Television technology, so understanding it makes those chapters shorter.
In everyday life: Look for Second audio program outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

Affiliate

Preply — study more efficiently by working with a personal tutor. 50% off.

How to study Second audio program in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Second audio program means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Second audio program out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Second audio program in simple terms?

Why does Second audio program matter?

Because it connects several engineering ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Second audio program?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Second audio program.