Your voice, your words, your attitude, and your body language all contribute to the image you project. In addition to visual cues, auditory cues—like the tone and quality of the voice, and choice of words—contribute to the all-important first impression.
On the telephone, however, the benefit of the visual cues is lost. The person on the other end of the telephone forms an image of you based solely on the tone and quality of your voice, and your choice of words.
With such limited information to go by, it is critical that you know how to use your voice and choose your words to project a positive image every time you place or receive a telephone call. The factors that impact image over the telephone are:
Vocal quality
Unless you're a singer or professional announcer, chances are you haven't given vocal quality much consideration. The timbre, rate, and pitch of your voice contribute to your vocal quality and to the image you project over the telephone as follows:

• Timbre—This is the combination of qualities of sound that make one voice different from another. A pleasant vocal timbre is flowing and melodious. It is clear, not scratchy or hoarse. People form a positive image when the person on the other end of the phone has a pleasant speaking voice.
   
• Rate of speech—The average English-speaking person speaks at a rate of 130-150 words per minute. Time yourself for comparison. It is difficult to understand a person who speaks very fast. When you speak too fast, words are hard to understand. Fast talking can occur when you get excited or emotional. Slow down to an average pace to give the best impression.
  If you speak very slowly, you may be giving the impression that you, yourself are slow or lazy. Picking up the pace should help you project a more positive image.
   
• Pitch—This is the highs and lows in a voice. In normal conversation, people vary the pitch of their voices to convey emotion or emphasize a word. A person with a high-pitched voice may sound young on the telephone and may have difficulty projecting an authoritative image.
  A low voice can sound harsh or even angry over the telephone. Remember to vary your intonation. No one wants to listen to boring, monotone speech patterns.

Vocal tone
Tone of voice uses the elements of vocal quality; timbre, rate, and pitch, to convey emotion or give meaning to the spoken word. Tone of voice conveys mood. If you are feeling angry, anxious, happy, sad, or any other emotion, chances are, it will be revealed in your tone of voice. Be careful you're not unintentionally creating a negative image with emotions that sneak into your vocal tone.
Use of appropriate words
The words you choose contribute largely to the impression you give over the telephone. To help ensure you choose your words well and project the most positive image, consider your vocabulary and your speech patterns.
It is easy to see the way choice of words impacts the image projected over the telephone. Every industry has its own terminology and jargon that could be confusing to the average person. If you're not speaking with someone from your field, limit the use of industry jargon, or at least be prepared to explain it.
The use of slang, regional phrases, or pop-culture phrases can create a negative image over the telephone by making you look sloppy, lazy, or too casual. Eliminating this kind of talk will help you project a more positive image.
When you're talking on the telephone, the person on the other end subliminally captures data and assesses your vocal quality, vocal tone, and choice of words. Based on that data, and all of its limitations, he forms an image of you, for better or for worse.
Being constantly mindful of your vocal quality and vocal tone will help you project a positive image over the telephone.