Visualizing Sound

Hi I am Darran Kelinske from Austin, TX in the USA. This lesson is for week 1 of Introduction To Music Production at Coursera.org. I will be teaching you about visualizing sound using Ableton Live and other tools available for MAC OS X.

In this lesson I will show you where to find different tools to visualize sound and explain some of the concepts related to visualizing sound. The tools we will explore in this post are an oscilloscope, spectrum analyzer, and sonogram.

Oscilloscope

To begin, we will look at an oscilloscope. An oscilloscope is used to visually display the waves that sound make in a medium. Time is displayed on the horizontal access and amplitude is displayed on the vertical access. By counting the number of waves for a particular 1 second time period we can express the frequency of the sound in hertz.

Using Ableton Live and a free plugin, Blue Cat’s Oscilloscope Multi, we can view the differences in frequency of each sound wave while playing different notes. After installing the plugin, I created a simple Grand Piano track that plays the note C on different octaves. The track can be seen below (click to expand).

Screen Shot 2014-02-06 at 7.23.20 AM

 

Now, let’s play the track while watching the Oscilloscope. We can see that when we play C4 we have around 10 peaks in a .02 second period.

Screen Shot 2014-02-06 at 7.27.59 AM

When we play C3, an octave below C4, we can see that there are five peaks in the same time period. As you go up by an octave the frequency doubles and as you go down by an octave the frequency halves. There is no correlation between amplitude and frequency.

Screen Shot 2014-02-06 at 7.30.21 AM

 

As we can see, one of the drawbacks of the oscilloscope is determining the frequency of a sound. This requires us to manually count and sum each peak in a one second time period.

Spectrum Analyzer

Next we will look at the spectrum analyzer using the same piano track that we were working with earlier. A spectrum analyzer measures frequency on the horizontal access and amplitude on vertical access. A Spectrum Analyzer is built into Ableton Live and can be accessed by performing a search for Spectrum in the top right.

Playing C3 while watching the spectrum analyzer shows that the largest peak is at around 262 Hz. If you hover over the peak Ableton will display the note and the frequency in the bottom left of the spectrum analyzer. While the mouse cursor is missing in the screenshot below, the peak that is seen here is C3 and is noted in the bottom left of the spectrum analyzer.

Screen Shot 2014-02-06 at 7.37.53 AM

Now, let’s play C2 which is an octave below C3. In the spectrum analyzer we can see that the frequency for C2 131, which is half of C3. This is in line with the observations we made while using the oscilloscope.

Screen Shot 2014-02-06 at 7.42.52 AM

One disadvantage of the spectrum analyzer is that it displays characteristics of sound at a particular time it and does not give you a picture of how sound is changing over time.

Sonogram

A sonogram allows you to view frequency, amplitude, and time in a single pane. Frequency is displayed on the vertical access. On the horizontal access time is displayed and on the z axis amplitude is displayed.

I was able to find a free sonogram called Sonic Visualizer to use for this post. After exporting our Grand Piano track (can be downloaded here: VisualizingSound), I loaded it into the Sonogram in Sonic Visualizer.

Here we can also see that as we play lower notes, the bottom frequencies of the sonogram are darker. We can also easily determine each particular note that is played as there is a distinct break between each note displayed on the sonogram. We can also see the harmonics that are related to each note.

Screen Shot 2014-02-06 at 7.54.47 AM

Thank you for reading my post on Visualizing Sound. This is a new domain for me and I enjoyed learning and writing about some of the ways we can visualize sound. All of the tools mentioned in this post come with free demo’s or are included in Ableton. If you have any questions, please comment below or contact me using any of the methods listed on the site. Thanks again.