Play sounds when a letter is shown
To implement typewriter sounds in your game, you can subscribe to the Typewriter’s “FOnCharacter” delegate and play sounds based on it.
The delegate passes a "FString" as a parameter, so you can play different sounds based on different letters as well.
P.S. The delegate is also triggered with spaces, so be sure to play sounds based on the type of character you prefer.
Example Plugin
As an example, you can download and enable the “TextAnimatorFebucciExtras” plugin from our website and check its implementation. Once downloaded, make sure the engine is closed and extract the contents of the .zip in this path of your project:
<your_project_root>/Content/Plugins/TextAnimatorFebucciExtras
Then open up Unreal again and it should detect the plugin in the plugin's list.
Inside the extras, you will find the Extra_TypewriterSound level, some audio clips and a Widget Blueprint. By opening and playing the level, you'll see some typewritten text which produces typewriting SFX. Finally, by opening the blueprint you can see how the example was implemented.

MinSoundDelay
Minimum time that has to pass before playing another sound
RandomSequence
If true, the next audio clip to play will be chosen randomly from the “Sounds” array. If false, sounds will be played subsequently
Sounds
Typewriter sounds to play