It is hard to hear the sound of your own voice. But that sound may affect other people's impressions of you even more than what you say.

A strong, smooth voice can enhance your chances of rising to CEO. And a nasal whine, a raspy tone or strident volume can drive colleagues to distraction. 'People may be tempted to say, 'Would you shut up?' But they dance around the issue because they don't want to hurt somebody's feelings,' says Phyllis Hartman, an Ingomar, Pa., human-resources consultant.

New research shows the sound of a person's voice strongly influences how he or she is seen. The sound of a speaker's voice matters twice as much as the content of the message, according to a study last year of 120 executives' speeches by Quantified Impressions, an Austin, Texas, communications analytics company. Researchers used computer software to analyze speakers' voices, then collected feedback from a panel of 10 experts and 1,000 listeners. The speakers' voice quality accounted for 23% of listeners' evaluations; the content of the message accounted for 11%. Other factors were the speakers' passion, knowledge and presence.

People who hear recordings of rough, weak, strained or breathy voices tend to label the speakers as negative, weak, passive or tense. People with normal voices are seen as successful, sexy, sociable and smart, according to a study of 74 adults published recently in the Journal of Voice. 'We are hard-wired to judge people. You hear somebody speak, and the first thing you do is to form an opinion about them,' says Lynda Stucky, president of ClearlySpeaking, a Pittsburgh coaching company.

Other common vocal irritants include 'uptalk' -- pronouncing statements as if they were questions -- and 'vocal fry' -- ending words in a raspy growl. Such quirks 'make the listener think the person who is speaking is either uncomfortable or in pain,' says Brian Petty, a speech pathologist at the Emory Voice Center in Atlanta.

Annoyed listeners often assume nothing can be done to change an irritating voice, and the speakers are often unaware of the problem. But in most cases, people's voices can be strengthened or improved through therapy, coaching or feedback.

Some voice problems have a medical cause, such as nodules on the vocal folds, or cords. A hearing impairment can cause people to talk too loudly, says Edie Hapner, director of speech-language pathology at the Emory Voice Center at Emory University. Also, advanced age can cause a person's voice to lose volume, she says.

But many voice problems can be eased through therapy, including exercises to support the voice through improved breathing, or to strengthen laryngeal muscles or change the way they work.

Speech pathologist Jayne Latz says she often receives requests for voice coaching after performance reviews in which a boss raises the issue as a problem for co-workers or customers. She uses sound-level equipment and audio recordings to make clients more aware of how they sound. She also teaches vocal exercises and helps clients replace filler words such as 'you know' with a pause for emphasis, says Ms. Latz, president of Corporate Speech Solutions, New York City.

New York financialexecutive Gerard Vignuli consulted Ms. Latz because he knew he spoke too fast, clipped the ends of words and often used filler words such as 'like' to give himself time to think, he says. 'When I was speaking, people didn't know what the hell I was saying,' he says. With coaching, 'I learned to step back and pause rather than saying, 'Uh, uh.' '

His friends noticed the difference: 'People didn't tell me until I started taking lessons, then they said they saw a difference. They said, 'Oh, we used to hate it when you said 'X,' ' he says. 'I said, 'Great! Why did you wait until now to tell me?'' Now, he asks friends to help him practice, telling them, 'Call me out' when they hear him lapse into old speech patterns.

People don't hear their own voices as others hear them. The voice must travel through the bones of the head before reaching the speaker's ears, changing the way it sounds, says Dr. Hapner.

Raising the issue can be touchy, Ms. Hartman says. Some people become defensive about their voices, saying, 'That's just the way I talk, and people shouldn't judge me,' she says. Also, sensitive factors such as gender, ethnicity, age and culturalbackground play a role in how people talk, and so managers should take care not to discriminate against an employee based on those characteristics, she says.

It helps to raise the topic on a positive note, such as, 'I admire the way you talk to clients. I've learned a lot by listening to you,' Ms. Hartman says. She suggests using an 'I-when you-because' formula when raising the problem, saying, 'I'm unable to think when you talk loudly because it's distracting to me.'

Work teams can sometimes help raise an employee's awareness, says Gillian Florentine, a human-resource consultant with Howland Peterson Consulting in Pittsburgh. A publishing-company sales team she worked with two years ago was disrupted by a rep whose voice boomed so loudly that co-workers couldn't hear clients on the phone, Ms. Florentine says. Co-workers in team meetings shared recordings of their calls, so the rep could hear himself in the background. He toned it down a bit, and agreed to a plan to rearrange their desks and place soundproof panels near his desk, she says. The problem was solved and the team has since been able to work smoothly together.

Ms. Florentine advises employers to screen job seekers based partly on their voices. Hiring managers typically focus on other factors, such as skills and experience, only to realize later than a new hire's speech patterns are annoying to co-workers or customers, she says.

When Jim Roddy interviewed Jon Dudenhoeffer five years ago for a recruiting job, he liked everything about him but his voice, says Mr. Roddy, president of Jameson Publishing, an Erie, Pa., publisher of trade magazines and websites.

'After the first half-hour, I had to put down my pen and say to him, 'We have a lot of high-energy, engaging people here, and I don't think they're going to like working with you because I can hardly hear you,' ' says Mr. Roddy, author of 'Hire Like You Just Beat Cancer.' He added, 'How about loosening up? People are going to think you have no pulse.'

Mr. Dudenhoeffer says he learned to speak in a low-key, deliberate tone during his 20-year stint as an investigator and trainer in the Air Force. He is also naturally reserved and has a calm, controlled manner. He was surprised that Mr. Roddy made an issue of his voice, but promised, 'Sure, I'll give it a try.'