Part of bringing a character to life is communicating emotions properly. On stage, you convey happiness with a smile and energetic movements, you can frown and drop your shoulders to show that you are sad, but none of that is available to the voice actor. You must do everything with your voice. Fortunately, you've all done exactly that in real life. You've spoken on the phone and people could tell how you felt if you weren't hiding it - at least if they knew you well enough.
Listen to each of the next three lines and see if you can tell what emotion is conveyed. One Two Three
It wasn't hard, was it? Even though the words gave no clue as to how the speaker was feeling, you could easily tell the difference between a happy voice, a sad voice, and a surprised one. You hear and recognize – and portray emotion all the time. The key with voice acting, as with stage acting, is to portray the emotion you want, when you want it.
Using Emotional Memory
Since we use emotions all the time, it might seem easy to use them in acting, but it's not. When we do emotions in real life, they come from within and are involuntary. We want the same outward expression without experiencing what actually makes us feel the emotions. The trick is emotional memory. The chances are that you will at one time or another have experienced any emotion you would need to portray. Try to remember a time when you were happy. Pay attention to how it feels in your body. For me, I note a swelling and lightness in my upper chest, I get a big smile on my face, causing the sides of my mouth to tighten, while my lips flatten on my teeth. My mouth opens slightly and my cheeks rise. When I want to act happy, I try to recall that feeling - when I speak while in that posture, my voice sounds happy. If I imagine myself happy enough, I may come close to laughing while I speak.
Sadness is a very different feeling. My mouth relaxes, my eyes lower, my shoulders sag a bit, and the tension goes out of my cheeks. When I speak in that position, my voice sounds sad. Sometimes it's hard to get words out and I stumble when I speak. It may be that you will feel the same things as I do; it may be that you react to these feelings differently. What matters is that put your body back to the same position it assumes when you genuinely feel the emotion. If you do it properly, you will feel at least a glimmer of that emotion automatically. But this is an important point: you need to build the feeling inside you to let the reactions work. This takes practice. If you try to force the tone or the hesitation, it will sound fake.
Practicing Emotional Deliveries
Try several emotions: happy, sad, angry, confused, frightened, horrified, love. Pick some memory of actually feeling those emotions. Fix it in your mind and note how your body reacts. Look at yourself in the mirror to see what your face is doing. Now try recording a short sentence with each of those emotions. When you play them back, do you hear the emotion. Note: pick a sentence that itself does not imply any particular emotion - you want your voice to do all the work, not the words.
This is something you want to turn into a reflex, so do this practice daily. You want to be able to think of the emotion and immediately have your face and neck and chest react. When you want to portray anger, your nostrils should probably flare. When you want to portray love, you should feel your heart warm up.
After you have done this for several days, pick a monologue and write down what emotions you want the character to be feeling and when. Then try to say that monologue using these techniques.