The Lombard effect is a pronunciation phenomenon which consists of the articulatory changes made by the speakers in order to be more intelligible in a noisy environment. As a usual consequence, it affects the normal intelligibility of a human speaker and degrades the performance of a speech recognizer. The main purpose of the study presented in this paper was to characterize the possible common tendencies of some acoustic features in different phonetic units for Lombard speech. For each feature and each phonetic unit well-known statistical tests were applied using a large Spanish continuous speech corpus. As a result, previously reported changes produced in Lombard speech with regard to normal speech are confirmed, in general. Nevertheless, some new clear and homogeneous tendencies have been observed.