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From Wikipedia, the free encyclopedia

Audio levels display on a digital audio recorder (Zoom H4n)
Audio levels display on a digital audio recorder (Zoom H4n)

Digital audio is sound that has been recorded in, or converted into, digital form. In digital audio, the sound wave of the audio signal is encoded as numerical samples in continuous sequence. For example, in CD audio, samples are taken 44100 times per second each with 16 bit sample depth. Digital audio is also the name for the entire technology of sound recording and reproduction using audio signals that have been encoded in digital form. Following significant advances in digital audio technology during the 1970s, it gradually replaced analog audio technology in many areas of audio engineering and telecommunications in the 1990s and 2000s.

In a digital audio system, an analog electrical signal representing the sound is converted with an analog-to-digital converter (ADC) into a digital signal, typically using pulse-code modulation. This digital signal can then be recorded, edited, modified, and copied using computers, audio playback machines, and other digital tools. When the sound engineer wishes to listen to the recording on headphones or loudspeakers (or when a consumer wishes to listen to a digital sound file), a digital-to-analog converter (DAC) performs the reverse process, converting a digital signal back into an analog signal, which is then sent through an audio power amplifier and ultimately to a loudspeaker.

Digital audio systems may include compression, storage, processing, and transmission components. Conversion to a digital format allows convenient manipulation, storage, transmission, and retrieval of an audio signal. Unlike analog audio, in which making copies of a recording results in generation loss and degradation of signal quality, digital audio allows an infinite number of copies to be made without any degradation of signal quality.

YouTube Encyclopedic

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Transcription

WARNING - COMPUTER GENERATED SUBTITLES one two three OBS just firing up my screen capture card stand behind please that look right this time start recording we are recording my screen I'm not multi-monitor sorry I'm not multi-monitor tonight not multi-camera it's just you and me with a little bit of lighting I can go really close mics I could do it like that want to now I'll do it on the side do it on the side like that a very good day ladies and gentleman I have fixed my audio problem um so we're not multi camera tonight we are low res on the monitor camera straight into the mixer strains of the camera on my last video I did if you weren't around the volume up were wearing headphones you could hear that did did he did they they did Adele it worried me so it's Thursday night now I've just released the film at she so I came to this little toy room here and I thought wonder why for what I've done wrong what we're done wrong now then so this is my monitor and this button here was unchecked that says PC right when I heard diddly-dee diddly-dee I thought you know I've heard that before and sounds like a yeah sounds a laptop under pressure now when I'm recording with all all the whole nine yards and I'll just check I am recording the moment to stop recording start recording yeah when I'm really pushing the boundaries the PC can be under a little bit of stress because it's not a super high spec laptop to be honest it's an Apple MacBook Pro by Windows on it I don't like Apple anyway whatever I bought it for the hardware because three or four years ago it was a really nice laptop for Windows um anyway the point is I'm just making this film to make sure you and I know that we don't leave you could turn the volume up in fact I'll shut up now you ready and will you turn the volume up and I'll give you a warning so I'm not gonna shout at you in a minute here we go I would suggest that was probably silence and I'm hoping it is so this is my channel strip here I'm on channel strip number three I'm plugged in it says three down here and into the mixing desk at the bottom eight bottom here because in a modern day a digital mixing desk has all you channel inputs and outputs and stuff and you have a to keep the cost down the the control surface it's bit like a flex radio isn't it and one of the reasons forget getting the by not having a control surface cuz a lot of the money off the price manufactured in the radio so that's why that works similarly the bearing X air 18 doesn't have a control surface now the one up from here and which is a slightly different league does have a control surface but it's also digital right but anyway you paint twice the money for it so I paid less than a thousand dollars I guess do this and what does it all do so in the old days you'd have a channel strip and he got all the control all the knobs all that we could all lit up the channel strip he and if he didn't know I'll just briefly explain what they are and you've got this one here which is my microphone going back a bucka bucka in a minute because an re xx needs quite a lot of mic gain it's not that hot so I wind the channel strip up effectively then you've normally got the slider haven't you so there's my slider down here which I keep about there so I can move that arm down with my M with my mouse I can give it a name here look which is very nice and then I got I can either drift off to the right or left and this is recorded in stereo so I'm hopefully I'm coming on your right hand speaker and now I'm coming on your left hand speaker because I've got the how do I get that to zero oh just move it because I'm coming into the camera in stereo right because I come straight out the hot PA what would normally drive your amplifiers shouldn't really be doing this but what hit me so I come out pretty hot on the mixer and that's why I'm down at - over here on the right hand side my about - 15 maybe a bit less I might say it though it says it there look at mine it's 60 boy 9 there may be - 17 how does that go away again I do that - if I click here go away - 16 1/2 LD hey we were on this channel strip then we've got these things so that is looks like a compressor so a quick that I've got my compressor so you can see what's happening is it's this it's a compressor backs off the de Peixe oh if I shout you see I'm going right over up to the top here but my compressors which is the red bit over here is pushing the volume back down so what's happening is doesn't matter how that I go it won't actually get any louder it's really cool your updates failed chunk because not connected to the incident right now I've got a problem connected to the internet or the mixer don't ask I'll fix you one day so that's a processor and that's I'm running the threshold at ten to one which frankly is very hot that's that's that's a lot the mix 100% in other words I only want the compressor I don't wear anything else and I'm running 6 DB gain after the processor to bring the level back up and that's how a audio processor kind of works if I switched it off you'll hear the difference the quick brown fox jumps over the lazy dog all good men should come to the aid of the party now off all good men should come to the aid of the party the quick brown fox jumped over the lazy dog well hey where's back to front but you hear a bit of a difference here I've also when I do my post-processing with Adobe Premiere that's gotten another processor on it as well and sometimes depending I've recorded it we'll also engage that so I am highly processed on the audio in terms of its compression so we were the mixer here the next one up is that one there and that's my EQ I've got a little lump I didn't know this until I went to here I don't remember doing this but this that's number two is this one here so I'm running minus 5 DB not a lot on a curve at one hundred and three hundred and twenty eight Hertz so I guess I must be taking the mud out my voice sir don't you bit closer see Alma so that's my EQ back to the mix again that one there is my noise gate so I take the noise gate off you might hear things like the fan on the on the laptops running at the moment because OBS studio is capturing there I don't know occasionally you can hear it so I'll keep the noise gate on on these settings and the red strip on the right here is the noise gate kicking in as I shut up so in fact maybe you know I don't really need to run the noise gate but hey I've got it I'll do I can also so that's my noise gate there I can also run across the top here I've got my EQ mic compressions for that channel strip okay so what else did they used to have um years ago I've got effects as well I've already want to run effects that's effects are these here see this four one two three four and there's my effects there one two three four in the bottom right and if I go to my effects so I'm run at EQ effects so I'm running some ambience on effects number one which is this one here so if I ran this is already fixed number one's already up here if I pull the ambience up I don't know where my headphones by guessing we've probably got some aliens later gentlemen you're live on the couch show so we're gonna take that off because I don't really want any run any effects it's really kind of dry and intimate okay so I could run lots of effects you know reverb and all sorts of things I can make my sound so myself sound like a Dalek you know whatever whatever I want so there we are we got various sends so we can come both take you through that that's not what's happening my mains out at the moment effects and then some meters so if you've got a whole van running on all the channels you see what's going on now I've got other microphones currently plumbed in at the moment on various channels but they're on mute look so like channel that I've got the pro 7 plumbed in there right now I've got hang on hey see how they them are you is you can see cuz up my whole drum kit is currently miked up and if I spoke loud enough and I'll try it now 1 2 3 you can see all the all the other channels coming up just just over here because all the other microphones picking me up but I'm on mute you see because I can snapshot this whole desk at the moment it's for me in the shack you know I've got you know the ts-990 into there if I wanted it you know whatever my lapel mic I'd plumbing here you know sm58 in there whatever blah blah blah blah blah and what I can do is I can snapshot this and go back to my oh I'm currently on YouTube or it could be the check or I could be the band the fat bastard's butt I'm not gonna do any of that I'm gonna get rid of it I've got various utilities and a lot of things I can copy all the settings from here onto here and so on is this any useful for a real Shack I don't know but over here is a little box of tricks because right now what I'm doing is I'm coming out the master so this set of driving magnifiers I come out the master and comes straight in to the camera and I wind the manual gain that don't even auto down to literally 0.01 so I'm coming in pretty hot into the camera but if you notice on the right hand side here my gain which I think I've talked about a minute ago you're running at Mikey's 19 - sixteen point nine comes straight into the camera but only on point one so the microphone gain on the camera the microphone preamp on the camera isn't working very hard because I've heard the mic gains on the camera isn't very good or I could do four wanted to do this for my ham Shack is that in in a real world when you use a mixing desk you've got these we spoke about these effects that I can wind up and down here but I've also got one two three four five six little strips here that I can use what the hell are they for well I've got six XLR outputs as part of not just my main left and right but I've got mono outs on six different channels so these are mark these are not these are monitor channels or what you can do is if I am the drummer I can say right well I want to hear the bass drum a lot and that might be much snare drum there I want to hear that quite well my cymbals I can I can't be bothered of them but I'm already here let's say my tom-toms little bit may say for tom toms then I've got the lead guitarist want to hear him quite well I want to hear the bass guitarists really well I want to hear the keyboards quite well one only the front vocals I want to hear the backing vocals and that's my monitor mix you see to me then the bass player might be on output number two so he might want to hear my bass drum my snare really well as well so he stays locked in he couldn't give a stuff about the rest of my stuff he just wants to hear I know whatever it is leave Ogle's very well because he might be doing backing so he wants to hear himself really well so these are all monitor settings and there's six channels on it so on the big mixing desk we used to have when you look down what the hell all those buttons fall and knobs a lot of them were for the monitor sends you might have a separate desk just for the monitor sense and and you would have EQ on a per channel strip of course a lot of the stuff I've got directly on here I go to and go to that channel there and go to my EQ just for that channel so a digital desk it gives you much more flexibility that's all so that's what there anyway can we use this for amateur radio well we could take a box like this and we could come out hot off the all come out one other monitors monitor the monitor sends into a little di box so it's a yeah a little isolation transformer if you like or it's not fully isolation transformer but we can we can we can add in the 40 DB of attenuation if we wanted to on here we come in there and out there come in there and out there straight into the rig I got a funny feeling that might isolate things because when I've gone through the desk of digital I've heard a little bit of RF on the audio chain I've got a funny feeling a little box like this might work very well we'll have to test out because it would be really funny to have like a echo and you could do some really nice processing we sharpen up the EQ and everything before I even entered the radio and of course that's what these ESS beat boys do isn't it the enhanced single sideband so they drive their radios really wide you know lots of Hertz nails you could use a little they use little four four band what you call it mixer but you can get I think an 8 channel one of these or six channel one of these a couple of hundred bucks you get all the nine yards on the front you can do what I do you could have your PC going into one you could have two or three different mic phones it'd be good with me I'm a pro seven permanently wired in and I just running this di box what does a DI box stand for it's an active splitter it does need am little battery or you can run it off the desk if the desk has got and but it won't be I might be using it like that yep it's a you know a lot of microphones that need what do they call it phantom power there we are so you could have phantom power but it won't run off hence part is he's one I was little 9-volt batteries so they're well food for thought we'll have to give it a go anyway there we are quick skim over hopefully I've sold my audio problem and next time I'll remember to switch off that button there so you won't hear the PC working over time so my name's Callum from DX Commander tune in next time for another episode of Callum at the controls - bye bye!

Contents

Overview

A sound wave, in red, represented digitally, in blue (after sampling and 4-bit quantization).
A sound wave, in red, represented digitally, in blue (after sampling and 4-bit quantization).

Digital audio technologies are used in the recording, manipulation, mass-production, and distribution of sound, including recordings of songs, instrumental pieces, podcasts, sound effects, and other sounds. Modern online music distribution depends on digital recording and data compression. The availability of music as data files, rather than as physical objects, has significantly reduced the costs of distribution.[1] Before digital audio, the music industry distributed and sold music by selling physical copies in the form of records and cassette tapes. With digital-audio and online distribution systems such as iTunes, companies sell digital sound files to consumers, which the consumer receives over the Internet.

An analog audio system converts physical waveforms of sound into electrical representations of those waveforms by use of a transducer, such as a microphone. The sounds are then stored on an analog medium such as magnetic tape, or transmitted through an analog medium such as a telephone line or radio. The process is reversed for reproduction: the electrical audio signal is amplified and then converted back into physical waveforms via a loudspeaker. Analog audio retains its fundamental wave-like characteristics throughout its storage, transformation, duplication, and amplification.

Analog audio signals are susceptible to noise and distortion, due to the innate characteristics of electronic circuits and associated devices. Disturbances in a digital system do not result in error unless the disturbance is so large as to result in a symbol being misinterpreted as another symbol or disturb the sequence of symbols. It is therefore generally possible to have an entirely error-free digital audio system in which no noise or distortion is introduced between conversion to digital format, and conversion back to analog.

A digital audio signal may optionally be encoded for correction of any errors that might occur in the storage or transmission of the signal. This technique, known as channel coding, is essential for broadcast or recorded digital systems to maintain bit accuracy. Eight-to-fourteen modulation is a channel code used in the audio compact disc (CD).

Conversion process

Analog to Digital to Analog conversion
The lifecycle of sound from its source, through an ADC, digital processing, a DAC, and finally as sound again.

A digital audio system starts with an ADC that converts an analog signal to a digital signal.[note 1] The ADC runs at a specified sampling rate and converts at a known bit resolution. CD audio, for example, has a sampling rate of 44.1 kHz (44,100 samples per second), and has 16-bit resolution for each stereo channel. Analog signals that have not already been bandlimited must be passed through an anti-aliasing filter before conversion, to prevent the aliasing distortion that is caused by audio signals with frequencies higher than the Nyquist frequency (half the sampling rate).

A digital audio signal may be stored or transmitted. Digital audio can be stored on a CD, a digital audio player, a hard drive, a USB flash drive, or any other digital data storage device. The digital signal may be altered through digital signal processing, where it may be filtered or have effects applied. Sample-rate conversion including upsampling and downsampling may be used to conform signals that have been encoded with a different sampling rate to a common sampling rate prior to processing. Audio data compression techniques, such as MP3, Advanced Audio Coding, Ogg Vorbis, or FLAC, are commonly employed to reduce the file size. Digital audio can be carried over digital audio interfaces such as AES3 or MADI. Digital audio can be carried over a network using audio over Ethernet, audio over IP or other streaming media standards and systems.

For playback, digital audio must be converted back to an analog signal with a DAC which may use oversampling.

History in recording

Pulse-code modulation was invented by British scientist Alec Reeves in 1937[2] and was used in telecommunications applications long before its first use in commercial broadcast and recording. Commercial digital recording was pioneered in Japan by NHK and Nippon Columbia and their Denon brand, in the 1960s. The first commercial digital recordings were released in 1971.[3]

The BBC also began to experiment with digital audio in the 1960s. By the early 1970s, it had developed a 2-channel recorder, and in 1972 it deployed a digital audio transmission system that linked their broadcast center to their remote transmitters.[3]

The first 16-bit PCM recording in the United States was made by Thomas Stockham at the Santa Fe Opera in 1976, on a Soundstream recorder. An improved version of the Soundstream system was used to produce several classical recordings by Telarc in 1978. The 3M digital multitrack recorder in development at the time was based on BBC technology. The first all-digital album recorded on this machine was Ry Cooder's Bop till You Drop in 1979. British record label Decca began development of its own 2-track digital audio recorders in 1978 and released the first European digital recording in 1979.[3]

Popular professional digital multitrack recorders produced by Sony and Mitsubishi in the early 1980s helped to bring about digital recording's acceptance by the major record companies. The 1982 introduction of the CD popularized digital audio with consumers.[3]

Technologies

Sony digital audio recorder PCM-7030
Sony digital audio recorder PCM-7030
Digital audio broadcasting
Storage technologies

Interfaces

Digital-audio-specific interfaces include:

Several interfaces are engineered to carry digital video and audio together, including HDMI and DisplayPort.

In professional architectural or installation applications, many digital audio audio over Ethernet protocols and interfaces exist.

See also

Notes

  1. ^ Some audio signals such as those created by digital synthesis originate entirely in the digital domain, in which case analog to digital conversion does not take place.

References

  1. ^ Janssens, Jelle; Stijn Vandaele; Tom Vander Beken (2009). "The Music Industry on (the) Line? Surviving Music Piracy in a Digital Era". European Journal of Crime. 77 (96): 77–96. doi:10.1163/157181709X429105. hdl:1854/LU-608677.
  2. ^ Genius Unrecognised, BBC, 2011-03-27, retrieved 2011-03-30
  3. ^ a b c d Fine, Thomas (2008). Barry R. Ashpole, ed. "The Dawn of Commercial Digital Recording" (PDF). ARSC Journal. Retrieved 2010-05-02.

Further reading

  • Borwick, John, ed., 1994: Sound Recording Practice (Oxford: Oxford University Press)
  • Bosi, Marina, and Goldberg, Richard E., 2003: Introduction to Digital Audio Coding and Standards (Springer)
  • Ifeachor, Emmanuel C., and Jervis, Barrie W., 2002: Digital Signal Processing: A Practical Approach (Harlow, England: Pearson Education Limited)
  • Rabiner, Lawrence R., and Gold, Bernard, 1975: Theory and Application of Digital Signal Processing (Englewood Cliffs, New Jersey: Prentice-Hall, Inc.)
  • Watkinson, John, 1994: The Art of Digital Audio (Oxford: Focal Press)

External links

This page was last edited on 5 February 2019, at 05:35
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