The Speech tab of Settings controls how Readable sounds.

Speech tab of Settings showing Voice set to System default, Rate, Pitch and Volume sliders, Silent mode, Test voice, and three Echo checkboxes.
Settings → Speech: voice, rate, pitch, volume, Silent mode and the Echo options.
Choosing a Voice
Pick any voice installed on your Mac. For Apple voices you can also set the rate, pitch and volume.
Silent Mode
Mute all of Readable’s speech without changing your other settings.
Key Echo and Voice Echo
Hear letters or words as you type, and hear your dictation read back.

Video help

A short video showing this feature in Readable for Mac v2. The video only contacts Vimeo once you press play.

Choosing a voice and adjusting how Readable speaks