Your voice can be the most powerful tool a photographer can have.  You need it to be confidently clear and loud enough for others to hear.  Its needed to coral groups together, to give direction, and to crack a little humor in the air to create smiles.  Far to many times have I seen shy photographers not being able to express what they wanted.  Using your fingers to point can help but it doesn't always help every situation.  Clients use us cause we know what we are doing.  Be confident and let that be heard in your voice.   It'll elevate your quality and your career will grow in the process.