08 mai 2014 ~ 0 Commentaires

Coursera – Music Production Week1 – Visualizing Sounds

In this post we will see the commons displays for a visual representation of sound

The 3 main different display to give us a good visual of sound are Oscilloscope, Spectrum analyzer and the Sonogram, let’s look in detail how they works :


Oscilloscope

On the oscilloscope we can see how the pressure is varying in the air (or voltage in a wire ).
The curve represent the speaker path through time.

Vertical axis is amplitude, horizontal is time.

We can found oscilloscopes integrated on every modern DAW :

if we zoom a lot on the oscilloscope we can see the waveform in detail
(example: a sawtooth waveform) :


Spectrum Analyzer

On the spectrum analyzer we can see the frequencies and their relatives amplitudes wich are a part of the timbre of a sound at a given moment.

The horizontal axis represents frequencies in Hz in the human ear range, vertical axis is the amplitude in dBFS.

Some spectrum analyzers will show a little more than the human ear range, Ableton Live’s one show frequencies from 10Hz to 24kHz

A limitation of the spectrum analyzer is when a wave is generating energy to a single frequency (example: a sinewave at 1kHz), it shows up as kind of a wide bump but there is only energy at this frequency.

In any periodic waveform like a sawtooth, the waveform is going to have peaks at a number of frequencies which is an integer multiple of the fundamental. ( if 1kHz is our fundamental we will have peaks at 2Khz, 3kHz, etc. ) This is called the harmonic series.
It’s an important component of the timbre.

We can often see this tools included in EQs or multibands plugins, where we are manipulating the timbre of a sound.

Common programs:

  • Voxengo SPAN (http://www.voxengo.com/product/span/)
  • Blucat audio FreqAnalyst ( http://www.bluecataudio.com/Products/Product_FreqAnalyst/ )

  • Sonogram

    A sonogram is like a spectrum analyzer with a view over time.

    It’s most of the time like a 90° flipped spectrum analyzer with an history of previous measurements.

    We can see the frequencies on vertical axis, the time on horizontal axis and the amplitude is represented by a color.

    Here an example of a NOT flipped one:

    With this tool we can look the frequencies produced by vowel sounds « A-E-I-O-U » and whats characterize them:

    We can see that the mouth is acting like a filter by removing or emphases certain frequencies !

    Common programs:

  • Melda mAnalyzer ( http://www.meldaproduction.com/plugins/product.php?id=MAnalyzer )
  • Sonogram SG-1 ( http://ag-works.net/plugins.sg1.htm )


  • There is also two other tools which can be very useful to represent some sounds properties :


    Goniometer

    This tool can be used to check stereo level of a sound, mono compatibility and detect phase problem.
    From wikipedia: « Its function is to plot a signal on a two-dimensional area so that the correlation between the two axes (audio channels, or phases) becomes apparent. »

    Common programs:

  • Flux – STT tools (http://www.fluxhome.com/products/freewares/stereotool)

  • Loudness History

    This tool can help you to monitor the loudness of your track over time.

    Common programs:

  • TC Electronics LM6 (http://www.tcelectronic.com/lm6-plug-in/)
  • iZotope Insight (https://www.izotope.com/en/products/mixing-mastering/insight/)


  • Thanks for reading ! I hope you liked’it and tell me whats the tools your using, if you use others !