The "t" sound inserted by some people in words like "thirteen" and "fourteen" is discussed in Message-ID: <bn4tavghvje7u36tp3p7lo7gtn2hks9qg4@4ax.com> and an ensuing thread.

The sound files are bc_13_thru_19.mp3 and bc_13_thru_19.wav.   I pronounce the words first with my normal pronunciation, then without the inserted "t".  I have no inserted "t" in "fifteen" or "sixteen".