Presentation skills in SA and your voice pitch during business presentations is part of the deal. Another suggestion is, perhaps diametrically contrary to what you might have been instructed in presentation skills classes, deliver the introduction in as normal tone as possible without taking recourse to any form of histrionics as early dramatic gestures generally tends to give a wrong impression - somewhat akin to the adage - empty vessels sound much. So, set the stage, draw the parameters and clearly define the goal as you begin your presentation and once you feel the audience is with you, gradually start unfolding all the armory at your disposal unleashing the slides one after the other as your voice changes pitch and rhetoric cascades from your lips right into the heart of the audience - important issued handled during presentation skills in SA. Anyone who has some experience in public speaking would sure acknowledge the importance of gestures and how a presenter can use his hands to significantly alter the tone and tenor of his presentation. A wide flowing gesture of hands from either side of the body till the palms meet each other with a soft but confident clasp convey an impression that the presenter is very knowledgeable about the  topic he is talking on and has some important information or observation to convey. The audience accordingly changes its mood and anticipation and it becomes that much easier for the presenter to take the audience along with him and convince the assembled people about the correctness of his viewpoint. These might sound rather different from standard practices taught in presentation skills in SA courses, but these have been garnered through years of practical experience in speaking to diverse audiences in varying environments.