Several years ago, studies on the acoustics of Spanish were difficult to find. A few early studies existed on microfilm (if you could find them), but these were few and far between. At last weekend’s NWAV, I saw a presentation on variation in Latin American Spanish vowel systems presented by Erin O’Rourke, whose 2005 dissertation fills a notable gap in the literature. A link to her webpage is given below, where you can find a number of her publications. It’s definitely worth a look.