Here is how the Keyboard.io model 01 sounds in both soft- and click-touch keys. While the camera angle changed between the two, the mic placement is the same and the volume levels reflect the subjective difference.

In both cases the mic was about a foot away from the keyboard, and the audio went through a dynamic range compressor, which gives the net effect of making the soft-touch ones sound a lot louder than they actually are. With an SPL meter I measure the soft-touch one at around 59dB and the quiet-click one at around 71 from the same respective differences - meaning the clicky keys are objectively a bit over 10x as loud.

See my related review of the Model 01, which also has links to the other input-related products visible: beesbuzz.biz/articles/43-Keyboard-io-Model-01