Representing sound as image
From TheStudentWiki
Music Production Analysis Index
Using graphic representations of sound can be helpful in analyis. A number of programmes now have the facility to look at waveforms, waveform spectrum and panning. The following examples are screenshots taken from Adobe Audition. Other software provide different images, but the basic principles are the same. In all cases, they are a 2D representation of the sound and as such, they have to be interpreted. However, they can be useful in focusing listening and revealing details of the production which would be difficult to discover otherwise.
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Waveforms
The following waveform represents a stereo image in two channels, left and right. On close inspection, you will see that the L-R waveforms are not the same. this is because the piece opens with drums and guitar. The mid-line in each channel represents 0dB and the waveform view can be useful to map dynamics.
Temptations, Cloud Nine (1968)
Waveform views can sometimes be useful for looking at structure, especially fade-ins and fade outs, but also structural contrast using dynamics.
Panning
This image is of the Kink's song, You Really Got Me Going and you will see that this is not a stereo image, but a mono image. The image here represents panning, but as it is a mono recording, the sound is located in the centre of the stereo field.
Contrast the image of the Kinks song with the panning used for Bjork's Hunter which uses extreme L-R panning and fills out the stereo image. The brigher sounds indicates intensity, so in Hunter, there are some intense sounds in the extreme Left and Right speakers.
Spectrogram or sonogram
A spectrogram or sonogram is a visual representation of a sound. In simple terms, a Fast Fourier transform is applied to an electronically recorded sound. The analysis separates the frequencies (represented on the vertical axis) and amplitudes (represented by intensity). Degrees of amplitude are represented light-to-dark with the lightest indicating the greatest energy (some sonograms represent this in reverse). The horizontal axis represents time. Here is the spectrogram for Bjork's Hunter
What is interesting in this example is how the intensity of the piece is in the middle section, In this way, the structure is not simply related to dynamics (getting louder) but also to the intensity of the harmonic spectrum as the frequency spectrum becomes wider and more intense.
Using images for analysis
The following images are from My Chemical Romance's song, Bury Me In Black. Each tells it's own story about the song.
The waveform shows the dynamic level of the music
The stereo image is quite interesting at the beginning as the sound from the left speaker almost disappears.
The spectrogram shows a very wide spectrum which comes from the distorted guitar sound. This is quite a different image to Bjork's Hunter.
It can take some time to develop the skills to read these images, but like musical notation, it allows you to focus your ears when listening to the production. Images such as these do not tell the whole story and they have to be interpreted. As such, care must be taken in using them.
