string phrase = @"<speak version=""1.0""
http://www.w3.org/2001/10/synthesis""
xml:lang=""en-US"">";
phrase += @"<say-as interpret-as=""ordinal"">3rd</say-as>";
phrase += @"<break time=""1s""/>";
phrase += @"<say-as interpret-as=""cardinal"">3rd</say-as>";
phrase += @"</speak>";
synthesizer.SpeakSsml(phrase);
https://docs.microsoft.com/en-us/archive/msdn-magazine/2019/june/speech-text-to-speech-synthesis-in-net