Answers to step 2.7

In the previous task you were asked to describe how you perceived three sound examples. In this step we use a sound visualisation technique called spectrograms to look more closely at the sound examples. We will return to discuss spectrograms more in detail in steps 2.13 and 2.14.

Sound example no. 1

Tapping with a ring on a fire extinguisher.

The sounds are impulsive, with an abrupt start and a slower (but still quite fast) decay. The tapping actions are also impulsive.

Below is a video showing a spectrogram of the sound file (also available here). We will look more closely at spectrograms later this week, but for now, notice that for each sound onset, a distinct vertical line is shown in the spectrogram. The horizontal lines that continue from the vertical lines are the partials in the sound.

Sound example no. 2

Rocks rubbed against each other.

Both the actions and sounds are of the sustained type, but if you listen carefully you will notice a grain-like quality to the sound which may be argued to be iterative

The spectrogram of this sound file looks quite different. The vertical lines are less distinct, and do not cover the entire vertical range. This indicates that the sound onset is slower, which is typical for sustained sounds, and that there is less high-frequency content.

Sound example no. 3

Marker pen on white board

Sustained actions and sounds when writing, but with short, impulsive sounds when the pen hits the board

The spectrogram of sound example number 3 is also different. There are impulsive low-frequency sounds each time the marker is put to the whiteboard. The spectrogram shows that the pitched squeeky sounds caused by the marker have more distinct partials than the rest of the sound file.