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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?"
chapter = false
weight = 3
#pre = "<b>1. </b>"
+++
**Ardour** is a digital audio workstation (DAW). Beforing using it to 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.
**Ardour** is a digital audio workstation (DAW). Beforing using it to
record and edit sound, it might be useful to review how digital audio
works.
## Frequency and Gain
@ -32,57 +17,61 @@ rest) backwards and forwards.
The number of times the membrane vibrates each second determines 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,
or _loudness_) of the sound. Normally, we measure frequency in _Hertz_ (Hz) and
amplitude in _decibels_ (dB).
![speaker membrane vibration](en/membrane-vibration.svg)
membrane travels from its resting point determines the _amplitude_ (the
volume, or _loudness_) of the sound. Normally, we measure frequency in
_Hertz_ (Hz) and amplitude in _decibels_ (dB).
Check out the great animation on this page illustrating this process:
{{< youtube RxdFP31QYAg >}}
A microphone works like a loudspeaker in reverse: vibrations in the air cause
its membrane to vibrate. The microphone turns these acoustic vibrations into
an electrical current. If you plug this microphone into a computer's sound
card and start recording, the sound card makes thousands of measurements of
this electric current per second and records them as numbers. The number of
_samples_ (i.e. measurements) made per second is called the _sample rate_, and
the number of possible values each sample can have is called the _bit depth_.
The combination of sample rate and bit depth indicates how closely the digital
signal can reproduce the sound it has recorded.
A microphone works like a loudspeaker in reverse: vibrations in the air
cause its membrane to vibrate. The microphone turns these acoustic
vibrations into an electrical current. If you plug this microphone into a
computer's sound card and start recording, the sound card makes thousands
of measurements of this electric current per second and records them as
numbers. The number of _samples_ (i.e. measurements) made per second is
called the _sample rate_, and the number of possible values each sample can
have is called the _bit depth_. The combination of sample rate and bit
depth indicates how closely the digital signal can reproduce the sound it
has recorded.
## Peaks and Clipping
When Ardour displays the samples which have been recorded, they appear as the
_waveform_ we see below. The center horizontal line indicates the membrane of
the speaker at rest, and the _peaks_ of the waveform indicate the maximum
_amplitude_.
When Ardour displays the samples which have been recorded, they appear as
the _waveform_ we see below. The center horizontal line indicates the
membrane of the speaker at rest, and the _peaks_ of the waveform indicate
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,
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.
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, 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,
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 %}}
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 %}}
The range of decibels between the region's maximum peak and the clipping point
is commonly referred to as _headroom_, and common recording practice is to
keep approximately 3 to 6 decibels of headroom between the maximum of your
signal and the clipping point, with the clipping point itself being
The range of decibels between the region's maximum peak and the clipping
point is commonly referred to as _headroom_, and common recording practice
is to keep approximately 3 to 6 decibels of headroom between the maximum of
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
comfortable amount of Headroom would have its maximum peaks between −6 dB and
−3 dB.
comfortable amount of Headroom would have its maximum peaks between −6 dB
and −3 dB.
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.
@ -115,3 +104,4 @@ Here is a great video tutorial explaining sampling rate and bit depth in a lot
more detail:
{{< youtube zC5KFnSUPNo >}}