[ˈɪstradˈɡənˈlaɪs]
Here's a breakdown:
* Ys is pronounced as "iss"
* tra is pronounced as "tra"
* d is silent
* gyn is pronounced as "gin"
* lais is pronounced as "laiss"
Therefore, it sounds like "iss-tra-gin-laiss".
Note: The English pronunciation of the town is often a bit different, with the "g" in "gyn" being pronounced, making it sound like "iss-trad-gin-lay-iss". However, the Welsh pronunciation is the correct one.