Here are a few of Rob Hagiwara's mystery spectrograms from 2003. OK, they aren't much of a mystery anymore, since I'm telling you what the sentence is and giving you a rough transcription. Your mission here is to decide which part of the spectrogram corresponds to each sound in the transcription.
Print out the spectrograms and draw lines between the sounds. (You can do it in your head if you're too cheap to print, but please don't go drawing lines on any computer screen owned by the university. Pen marks are so hard to wash off.)
Then click on the link to go see how Rob segmented the spectrogram, and read his discussion of each sound, how it appears on the spectrogram, and the peculiarities of the pronunciation of Rob-ese. (His transciptions are usually a bit narrower than the ones I give below.)
When you're done with these, try your hand at guessing the sentences for the gazillion other spectrograms on Rob's site.
It left a greasy stain.
[ɪt ˈlɛft ə ˈɡɹisi ˈstejn]
They like iced tea with lemon.
[ðe ˈlajk ˈʔajs ˈtʰi wəθ ˈlɛmən]
The damage reduces the value.
[ðə ˈdæmədʒ ɹəˈdusəz ðə ˈvælju]
Prairie folk are hardy folk.
[ˈpʰɹɛɹi ˈfok ʔɑɹ ˈhɑɹɾi ˈfok]
(This one has the formants highlighted for you!)