2. PRESENTING THE PRESENTATION
• Hi! I’m Rodrigo De la Prida from
Santiago, Chile. The present lesson
is for week 1 of Introduction To
Music Production, at Coursera.org,
and is about the different ways of
visualizing sound.
I hope you enjoy!
3. • A visual representation of sound helps us understand what we hear. We can see
parameters such as frequency, amplitude and timbre, and how they are affected by
processing sound.
4. THE WAYS
• We will discuss the main and most used ways for the visual representation of sound,
and the digital electronic devices responsible for show it to us. These devices are the
Ocilloscope, the Spectrum Analyzer, and the Sonogram.
Let’s see them!
5. THE OSCILLOSCOPE
• This device presents a very detailed
representation of the sound, in real
time, and in 2D.
• The values of the audio signal are
displayed as coordinates through a
screen, what we know as
oscillogram. The X axis (horizontal)
represents time, and the Y axis
(vertical) represents amplitude (dB,
dBFS). Analog
Oscilloscope
6. • Of course, in our computer
we use digital oscilloscopes.
For example, this one, a free
oscilloscope for Max for
Live:
Jo.Oscilloscope, by Jonas Obermüller
• Or this one, also free:
S(M)exoscope, by SmartElectronix
[Click in the images for downloads]
7. • In the oscillogram we can view sine, triangular, square, and saw tooth waveforms,
and appreciate how the shape is different between them.
Sine waveform Triangular waveform
Saw Tooth waveform Square waveform
8. • The main limitation with the oscilloscope is related with the frequency analysis. We
really can’t see it clearly, because the view is so microscopic. Generally we can only
see a very small part of a second, or a full second, and counting the repetitions of a
wave cycle in every second seems pretty impractical.
• So, in order to see and analyze the frequency of the signal, we really need another
device, called Spectrum Analyzer.
9. THE SPECTRUM ANALYZER
• With the Spectrum Analyzer is
possibly to see several spectral
components of the audio signal,
like bandwith, dominant
frequency, and harmonics.
• The frequency of the signal,
measured by Hertz, is showed
through the horizontal axis, or
X, and the amplitud in the
vertical axis, or Y.
Analog Spectrum
Analizer
10. • With the Spectrum Analyzer we can appreciate the differences in the harmonic
content, between the four audio waveforms: sine, square, triangular, and saw tooth.
Sine waveform
• Basically we see the fundamental frequency and the absence of harmonics, which
defines sine waves. Look at the bottom left corner. In this orange square the
Spectrum, from Ableton Live, shows the frequency (262 Hz), note pitch and octave
(C3), and the amplitude (-13.7 dB).
11. Square waveform
• In this waveform we can
see several harmonics
added to the fundamental
frequency. Specifically, odd
harmonics.
Non-sinusoidal waveforms
Triangular waveform
• Also with odd
harmonics, but the
higher ones roll-off
much faster than in a
square wave.
13. • The Spectrum Analyzer is widly use for the frequencies analysis in filters. It’s very
common see them in the displays of the equalizers.
EQ Eigth, from Ableton
Live.
Pro-Q2, from fabfilter.
14. • Here are a couple of examples of Spectrum
Analyzers:
SPAN, by Voxengo
[Click in the images for free
downloads]
FreqAnalyst, by Blue Cat
Audio.
15. THE SONOGRAM
• With this device we can see the
audio signal evolution in time.
• Now, the frequency of the signal
is showed through the vetical
axis, or Y, and the time is
showed in the horizontal axis, or
X. Also it has another axis, the Z,
and it represents the amplitude
with colors.
Sonogram View
16. • The color range goes from the blue, for the
minimum amplitude, to the red, the maximum.
• We can see that in this sonogram of
an American Goldfinch:
17. • Here are two examples of software that offers the sonogram
view:
Lab TS, by IRCAM. The Snail, by
IRCAM.
18. This presentation was made for the Coursera.org course “Introduction to Music Production”.
Santiago, Chile, February - 2016
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