Hi - you can use SSML prosody tags in the text to control the speed.
This will not work with all voices though - so you may need to experiment. Here's an example -
You surround your text with the brackets as you see below - and it will speak slower.
<prosody rate="slow"> hello there 1 2 3 4 5 6 7 8 9 </prosody>
For more fine tuned control, use the following syntax (supported by a further subset of voices)
<prosody rate="-10%"> hello there 1 2 3 4 5 6 7 8 9</prosody>
As noted - only a subset of the voices will respond. Supported voices include -
Let me know how goes.
Servicio de atención al cliente por UserEcho