iron tones

For learning how to pronounce tones, the most common difficulties are not starting high enough on the fourth tone (which is a falling tone) and believing what well-meaning Chinese tell you about how the third tone is a "dipping" tone (it isn't, and I've got the hours in the phonetics lab to be able to say this -- it's most often although not absolutely always a short, low tone or a short low toen with a slight falling tendency). I think for most Westerners, it's easier to get your head around "first tine is really high and stays high, second tone starts very low and rises, third tone is short and very low, fourth tone starts really high and falls" than to be talking about dipping third tones.