When the audience has to work too hard to hear you they will eventually give up. I continue to be amazed by bad sound systems at schools, churches, hotels, corporate auditoriums, and community events. Or the soft spoken speaker who thinks that because they have a microphone they don’t need to speak up and project. Test systems ahead of time to be sure the folks in the back of the room or area can hear loud and clear. Check again once the audience is there. Losing half the audience due to poor sound will create a ripple effect of distractions that will throw off even the folks that can hear.  Soon they’ll all just be waiting for it to be over.