A business communication coach could be inclined to say the following:
I think you should speak with more volume, and by the way, using correct intonation patterns is not enough. Think about the words that you think are important and give them some added stress or added volume. This helps your audience to remain focused on your presentation. Speaking in a monotone at a low volume is not going to make what you have to say at a meeting or at a presentation convincing and will not effectively convey your message.
English language speakers are very much in the habit of using emphatic stress, contrastive stress, and new information stress. This keeps listeners focused on the speaker. Added expression is imporant. It goes hand in hand with the content. Added expression helps you say what you want to say, it gets your point across more effectively, and most important of all, it keeps the listeners interested in you and your message.