After turning on Speak Selection to enable text-to-speech, or enabling Speak Screen to hear the screen content in your iPhone or iPad, you can speed up or slow down the speaking rate depending on your own need. As for how to make it, please refer to the following instruction.
Steps to adjust speaking rate of Speak Selection or Speak Screen in iPhone and iPad:
Step 1: Get into SettingsGeneralAccessibilitySpeech (or Speak Selection).
Step 2: Under SPEAKING RATE, move the tool on the scale to the left or the right to slow down or speed up the rate, as shown in the picture below.
