Here is some evidence that auditory subliminal can work...
quote:
Likewise, auditory stimuli such as the names of letters were whispered so faintly that observers claimed that they were unable to hear any sound whatsoever. To test whether these visual or auditory stimuli may have been perceived despite the statements to the contrary, the observers were asked to make guesses regarding the stimuli. For example, if half the stimuli were letters and half the stimuli were digits, the observers may have been asked to guess whether a letter or a digit had been presented. The consistent result found in these early studies was that the observers' guesses regarding the stimuli were more correct than would be expected on the basis of chance guessing. In other words, despite the observers' statements indicating that they were unaware of perceiving the stimuli, their guesses indicated that they did in fact perceive sufficient information to make accurate guesses regarding the stimuli. Over the years, there have been literally hundreds of studies following a similar format. Taken together, these studies show that considerable information capable of informing decisions and guiding actions is perceived even when observers do not experience any awareness of perceiving.

http://watarts.uwaterloo.ca/%7Epmerikle/papers/SubliminalPerception.html
Check out the link for more details (I love these University sites always have plenty of reading material ;D)

Alex