It's the way you say it

the long version

The only way that people can sense your intelligence and professionalism is through the effectiveness of your communication, what they hear you say, the attitude that is perceived, and the very sound of your voice. Learn how to work specifically with your speech and your voice. Ideally you want your body, your words, and your voice to all be communicating the same thing at the same time. That is what comes across as professional, trustworthy, and appealing.