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Remove illustrations, they are confusing and not very helpful

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Alexandre Prokoudine 2022-04-24 23:33:58 +03:00
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content/introduction/what-is-digital-audio/index.en.md
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@ -3,26 +3,11 @@ title = "What is digital audio?"
description = "What is digital audio?" description = "What is digital audio?"
chapter = false chapter = false
weight = 3 weight = 3
#pre = "<b>1. </b>"
+++ +++
**Ardour** is a digital audio workstation (DAW). Beforing using it to record and **Ardour** is a digital audio workstation (DAW). Beforing using it to
edit sound, it might be useful to review how digital audio works. record and edit sound, it might be useful to review how digital audio
works.
![analogue-digital](en/adc-dac.svg)
<!-- {{<mermaid align="center">}}
graph TD;
A(fa:fa-microphone Analog input) --> B(Analog to digital conversion)
B --> | digital numeric data, samples | C(Digital system)
C --> D(Digital to analog conversion)
D --> E(fa:fa-headphones Analog output)
{{< /mermaid >}} -->
The diagram above shows how sound travels to and from your computer. The
"Analogue to Digital Conversion" (ADC) and the "Digital to Analogue
Conversion" (DAC) are done by the sound card or audio interface. The digital
system in this case is your computer running Ardour.
## Frequency and Gain ## Frequency and Gain
@ -32,57 +17,61 @@ rest) backwards and forwards.
The number of times the membrane vibrates each second determines the The number of times the membrane vibrates each second determines the
_frequency_ (the note, or _pitch_) of the sound you hear. The distance the _frequency_ (the note, or _pitch_) of the sound you hear. The distance the
membrane travels from its resting point determines the _amplitude_ (the volume, membrane travels from its resting point determines the _amplitude_ (the
or _loudness_) of the sound. Normally, we measure frequency in _Hertz_ (Hz) and volume, or _loudness_) of the sound. Normally, we measure frequency in
amplitude in _decibels_ (dB). _Hertz_ (Hz) and amplitude in _decibels_ (dB).
![speaker membrane vibration](en/membrane-vibration.svg)
Check out the great animation on this page illustrating this process: Check out the great animation on this page illustrating this process:
{{< youtube RxdFP31QYAg >}} {{< youtube RxdFP31QYAg >}}
A microphone works like a loudspeaker in reverse: vibrations in the air cause A microphone works like a loudspeaker in reverse: vibrations in the air
its membrane to vibrate. The microphone turns these acoustic vibrations into cause its membrane to vibrate. The microphone turns these acoustic
an electrical current. If you plug this microphone into a computer's sound vibrations into an electrical current. If you plug this microphone into a
card and start recording, the sound card makes thousands of measurements of computer's sound card and start recording, the sound card makes thousands
this electric current per second and records them as numbers. The number of of measurements of this electric current per second and records them as
_samples_ (i.e. measurements) made per second is called the _sample rate_, and numbers. The number of _samples_ (i.e. measurements) made per second is
the number of possible values each sample can have is called the _bit depth_. called the _sample rate_, and the number of possible values each sample can
The combination of sample rate and bit depth indicates how closely the digital have is called the _bit depth_. The combination of sample rate and bit
signal can reproduce the sound it has recorded. depth indicates how closely the digital signal can reproduce the sound it
has recorded.
## Peaks and Clipping ## Peaks and Clipping
When Ardour displays the samples which have been recorded, they appear as the When Ardour displays the samples which have been recorded, they appear as
_waveform_ we see below. The center horizontal line indicates the membrane of the _waveform_ we see below. The center horizontal line indicates the
the speaker at rest, and the _peaks_ of the waveform indicate the maximum membrane of the speaker at rest, and the _peaks_ of the waveform indicate
_amplitude_. the maximum _amplitude_.
![waveform](en/Ardour4_Digital_Audio_Waveform.png) {{< figure src="en/Ardour4_Digital_Audio_Waveform.png" alt="Waveform" >}}
If we take a waveform and increase its amplitude a lot, some of the peaks may now fall outside the range that the computer can represent digitally. The computer's inability to represent peaks outside the range of amplitude is called _clipping_, which results in a permanent loss of digital information, If we take a waveform and increase its amplitude a lot, some of the peaks
as well as a change in the sound quality which is recognizable as may now fall outside the range that the computer can represent digitally.
_distortion_. Ardour marks clipped peaks with the color red, as can be seen in The computer's inability to represent peaks outside the range of amplitude
the image below. is called _clipping_, which results in a permanent loss of digital
information, as well as a change in the sound quality which is recognizable
as _distortion_. Ardour marks clipped peaks with the color red, as can be
seen in the image below.
![clipping](en/Ardour4_Digital_Audio_Clipping2.png) {{< figure src="en/Ardour4_Digital_Audio_Clipping2.png" alt="Clipping" >}}
In the image above, one can also see the _mixer strip_ on the far left, In the image above, one can also see the _mixer strip_ on the far left,
which gives a running measurement of the peaks, as well as an indication which gives a running measurement of the peaks, as well as an indication
at the top of the _peak meters_ showing the maximum peak so far. The red number indicates clipping has occurred. at the top of the _peak meters_ showing the maximum peak so far. The red
number indicates clipping has occurred.
{{% notice tip %}} {{% notice tip %}}
Clipping often can happen at the time of recording if you set your microphone levels too high. Clipping often can happen at the time of recording if you set your
microphone levels too high.
{{% /notice %}} {{% /notice %}}
The range of decibels between the region's maximum peak and the clipping point The range of decibels between the region's maximum peak and the clipping
is commonly referred to as _headroom_, and common recording practice is to point is commonly referred to as _headroom_, and common recording practice
keep approximately 3 to 6 decibels of headroom between the maximum of your is to keep approximately 3 to 6 decibels of headroom between the maximum of
signal and the clipping point, with the clipping point itself being your signal and the clipping point, with the clipping point itself being
represented as 0 dB (zero decibels). In other words, an audio region with a represented as 0 dB (zero decibels). In other words, an audio region with a
comfortable amount of Headroom would have its maximum peaks between −6 dB and comfortable amount of Headroom would have its maximum peaks between −6 dB
−3 dB. and −3 dB.
Also, because the peaks of audio signals add together, care must be taken when Also, because the peaks of audio signals add together, care must be taken when
_mixing_ several sources together to keep the combined signals from clipping. _mixing_ several sources together to keep the combined signals from clipping.
@ -115,3 +104,4 @@ Here is a great video tutorial explaining sampling rate and bit depth in a lot
more detail: more detail:
{{< youtube zC5KFnSUPNo >}} {{< youtube zC5KFnSUPNo >}}