At ECG, we spend most of our professional lives helping clients craft compelling evidence-based arguments. Having a clear, well-structured argument, tuned to the needs, interests, and attitudes of the audience is a critical aspect of persuasion.

However, there is another aspect of persuasion that determines the outcome of a presentation, delivery. Multiple studies have demonstrated that a speaker’s use of nonverbal cues has a direct effect on their ability to convince an audience. Several recent studies have shown that the mechanism by which these cues operate on the audience is by conveying the speaker’s confidence in what they are saying. And one recent study has determined the element of the communication delivery that appears to have the greatest effect is the voice.

Specifically, louder volume and greater variations in volume do the most to convey the confidence of the speaker and result in greater persuasive impact.

This new research is completely consistent with what we teach in our training seminars and private coaching sessions. We encourage participants to use greater volume whenever they are addressing a group, plus we encourage them to be expressive with their voices by varying volume, both for clarity and for emphasis. In working with clients on their vocal delivery, we also work on varying pitch, pace, and pausing. But recent research suggests that the greatest impact on persuasion comes specifically from the use of volume.

Let's review three simple steps for using volume to persuade in the delivery of a presentation:


It seems simple enough, but most speakers actually tend to speak too softly when they present. Under pressure, many people tend to tense up, breathe more shallowly, and tighten their jaws. Vocal warm-ups can help break up this tension and improve breathing.

It’s best to warm up as close to the start of the presentation as possible. As you begin the presentation and throughout your delivery, make sure you take deep, diaphragmatic breaths and then use a lot of air in the creation of each syllable of sound. This will generally result in needing to take a breath more often which ties nicely into the technique of pausing between phrases. Those pauses are great because they add weight to your words and give them a chance to sink in for your audience.


Next, open your mouth.

When you’re presenting, you should generally be bigger and louder than you would be in normal conversation. This applies directly to the use of your mouth to create sound. The further you open your mouth, the more air can pass through it as you speak, and the louder your voice will be. It is that simple! But it’s not always that easy, largely due to the muscle tension arising from anxiety that fights against the big open mouth. It can also be a challenge for people who typically speak through a tight jaw or clenched teeth.


In order to make sure that the tension you dissolved during the vocal warm-up doesn’t creep back into your delivery, make sure you move to break up any tension before it takes hold. Specifically, look for opportunities to make large gestures from the shoulder that break up tension in the neck, jaw, and vocal apparatus. Plus, when possible, take a few steps, moving your whole body as part of your delivery. Whole body movement does the most to break up tension and release the energy that can cause it.

By using these simple techniques, you will be able to use greater volume overall and to emphasize key points, boosting your audience’s perception of your confidence and your persuasive impact.