When you’re writing you need to avoid the use of too many speech tags and adverbs as those will weaken your writing.
To develop a character we sometimes forget that the sound of their voice also plays into who they are and how they come across to the reader.
Here are five suggestions on how to make a voice unique.

CELEBRITY OR KNOWN VOICES:
Does your character have a similar voice to a celebrity or well-known person? Perhaps they have a wispy, breathy voice like when Marilyn Monroe famously sang Happy Birthday. Or maybe they sound high-pitched and tight like Mickey Mouse.
Choose someone that people will be familiar with and then that voice will be attached to your character.
NATURE:
Is the voice breathy? dewy? chilly? earthy?
Take the word and bring it to life. For example: Her voice reminded me of a night ’round the campfire–warm, smokey, and tinged with a bit of fire when she got angry.
Do you now have that woman’s voice, and personality, in your head?
How about a feather? wispy, light, and ticklish.
MEDICAL:
Think of terms used in the hospital. What does a terminal patient sound like? Flat? Deflated?
The voice could be piercing like a needle or drip like an endless IV or perhaps its tinged with authority like that of a doctor ordering medications.
Think about a care-givers nature and the voice they use to sooth patients.
The sound of a voice could relate to fear, uncertainty, or sadness. Close your eyes and picture those scenes and what those people sound like. How would you describe their voice. Is that how your character sounds?
THE WORLD:
Is there an accent? Does your character come from another country? Maybe they have a twang or pull their vowels slowly through the word so you need to listen really closely. Do they sound like a desert? What does that sound like to you?
You can use your other senses here too. Her voice sounded like endless machine gun fire as it peppered me with questions.
or
The smell of horse manure brought memories of his foul mouth.
THE INDIVIDUAL:
Take a look at the character for clues. Are they young? unsure of themselves? Maybe they talk like their mouth is full of bubblegum or covered by a mask. What is their motivation and who are they?
If they’re a force to be reckoned with then that will be reflected through their voice. Their voice may reverberate off the walls as they laugh or make a joke…. Find something to compare it to like a monster truck or small earthquake.
Remember too that other characters can help identify the voice of characters. Imagine a grumpy old man saying: Speak up girl, you sound like a new born kitten with its tail between its leg.
To me that paints a picture of a frightened and shy little one who doesn’t make eye contact…
So have fun. I hope this helps a bit. Remember the key is to show don’t tell but sometimes it’s okay to throw in an adverb here and there if you have to.
Thanks for reading My Twisted Writer Brain.