You may have written some difficult voices into your book. (“John spoke with a gravely voice, a result of a pack a day for 20 years.”). You are obligated to give that characteristic some presence. You don't have to overdo it, but you have to at least give a hint of it.

Here are some characteristics that you may have given your characters' voices by description. Practice the ones you used in your book:

• High tinny voice (for men)
• Deep (for women)
• Young child's voice
• Old person's voice (cracks)
• Hoarseness / roughness /raspiness
• Breathiness
• Speaking on inhalation
• Drawl

If your character's voice is similar to something you have seen on tv or in a movie, watch it, and make special note of that character. If possible, make a recording, so you can listen to it several times and try to copy the sound of it.

If you are a man trying to do a woman's voice, use a very slightly higher pitch. Too much will sound unnatural. Avoid using a falsetto.

If you are a woman trying to do a man's voice, use a very slightly lower pitch. Too much will also sound unnatural. Avoid trying to sound too barrel chested.