Week 2 Bench: Listening for keys

Recording a keyboard, and finding out how much of what was typed survives in the sound alone

1 March 2027

Before the Bench#

Record yourself typing a short, known passage on a keyboard — phone audio is enough. Keep the passage text; you will need to check your recording against it later.

In the Bench#

Pull the recording into a waveform viewer and align it, keystroke by keystroke, against the passage you typed. Some keys are visibly distinct by ear alone — the spacebar, the largest keys, anything near the recorder. The exercise is not to build a classifier; it is to see, directly, that a microphone captures more than it was pointed at.

Afterwards#

Bring your annotated waveform to next week’s lecture, which puts a name and a disclosure history to what you just did by hand.