Audio signal flow: Difference between revisions

Revision as of 05:07, 10 October 2016

Revision as of 11:02, 17 November 2016

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'''Audio signal flow''' is the path an [[sound|audio]] signal takes from source to output.<ref>{{cite book | title = Pro Tools 6 for Macintosh and Windows | author= Steven Roback | edition = 2nd | publisher = Peachpit Press | year = 2004 | isbn = 978-0-321-21315-0 | page = 303 | url = https://books.google.com/books?id=6kcD7mPdaXwC&pg=PT319&dq=%22audio+signal+flow%22&lr=&num=20&as_brr=3&ei=Fe47S-TAFYrSkwTjy5DMAQ&cd=2#v=onepage&q=%22audio%20signal%20flow%22&f=false }}</ref> The concept of audio signal flow is closely related to the concept of audio gain staging; each component in the signal flow can be thought of as a [[gain stage]].

In typical home stereo systems, the signal flow is usually short and simple, with only a few components. However, in recording studios and performance venues, the signal flow can often be quite complicated, with a large number of components, each of which may cause the signal to fail to reach its desired output. Knowing each component in the signal flow becomes increasingly difficult and important as system size and complexity increases.

== Feedback ==

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[[File:Singer Signal Flow Example.png|thumb|center|550px|Singer Signal Flow Example]]

The first element in the signal flow is the vocalist, which produces the signal. This signal propagates acoustically to the microphone according to the [[Inverse-square law]], where it is converted by a transducer into an electrical signal. Other objects may also produce sound in the acoustical environment, such as [[HVAC]] systems, computer fans, traffic noise, elevators, plumbing, etc. These noise sources arecan also be picked up by the microphone. It is therefore important to optimize the acoustical signal/noise ratio at the microphone. This can be accomplished by reducing the amplitude of unwanted noise (for example, turning off the HVAC system while recording), or by taking advantage of the inverse-square law; by moving the microphone closer to the signal source and farther away from any noise sources, the signal/noise ratio is increased.

After the microphone, the signal passes down a cable to the microphone preamplifier, which amplifies the microphone signal to line level. This is important because a line-level signal is necessary to drive the input circuitry of any further processing equipment down the chain, which will generally not be able to accept the extremely low-voltage signal produced by a typical microphone.

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For the purposes of this example, the output of the microphone preamplifier is then sent to an EQ, where the timbre of the sound may be manipulated for artistic or technical purposes. Examples of artistic purposes include making the singer sound "brighter," "darker," "more forward," "less nasal," etc. Examples of technical purposes include reducing unwanted low-frequency rumble from HVAC systems, compensating for high-frequency loss caused by distant microphone placement, etc.

The output of the EQ will then be sent to a compressor, which is a device that manipulates the dynamic range of a signal for either artistic or technical reasons.

The output of the compressor is then sent to an analog-to-digital converter, which converts the signal to a digital format, allowing the signal to be sent to a digital recording device, such as a computer.

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== Broadcast Performance Signal Flow Example ==

In this example, we will explore the signal flow of a hypothetical rock concert. For our example, this concert not only has a live audience, it is also being broadcast on live TV, and it is being recorded, with copies of the recording being sold to the public immediately after the concert is over. The signal from each microphone is therefore being sent to five places; the house sound system, the in-ear monitor system for the performers, the broadcast system, the recording system, and to the lobby, restrooms, and backstage areas so that people can hear the performance while outside the performance area.

[[File:Broadcast Example Overview.jpg|thumb|center|550px|Overview diagram of Signal Flow for this example.]]

The house sound system will be controlled from the "Front of House" position, also called the "Mix position." This position is usually located behind the audience.

[[File:View from Front of House.jpg|thumb|none|The view from the Front of House Position.]]

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[[File:Dunkys monitor world at Soundwave 2010.jpg|thumb|none|An example of a monitor mix position]]

The broadcast mix will be controlled from a broadcast truck, located in the parking lot behind the performance venue.

[[File:Arena_OB7.JPG|Arena Television OB8 working for the BBC at Wimbledon Tennis Championships, UK|thumb|none|An example of a broadcast truck.]]

The recording system will be located in another truck, located next to the broadcast truck.

For this example, the lobby, restroom, and backstage mix will be controlled by an assistant stage manager from backstage.