Whispered speech is characterized as having no vibratory movement of the vocal folds. Many studies, however, report significant acoustic differences between whispered and normal speech which are not an obvious consequence of differences in phonation. For example, the first formant has been shown to be higher in spectral frequency during whispering as well as lower in amplitude relative to the other formants. These tendencies were both confirmed. The hypothesis that these and other acoustic effects are caused by the non-glottal articulatory effects of increased vocal effort (jaw lowering, fricative constriction, larynx raising, etc.) was tested using electromagnetic articulography and electroglottography. Some acoustic differences correlated well with non-laryngeal articulatory differences. The acoustic differences, however, could not be entirely accounted for by non-glottal articulatory features. Whispering clearly exhibited articulatory features similar to high vocal effort normal speech, but glottal articulation seems to also play a part in the acoustic differences by affecting acoustic coupling to the subglottal vocal tract.