When people talk about the voice of a designer, they are usually referring to their ability to communicate through a visual medium. We are relied on for our visual skills, it is at the very core of what we do, but our ability to verbalize our processes is equally important.
There are a couple of phrases I say around the office a lot: If you don't talk about design, no one is going to understand its value; and, the quickest way to kill design in an organization is to not talk about design.
My point in reciting these mantras is two-fold (one is strategic and one is tactical).
1. Talking about design makes it more approachable.
By having discussions around design (especially with non-designers) you elevate the overall level of education and discourse that others have on the topic. Generally, people are less inclined to have conversations about a domain they know nothing about. However, if they feel they have some understanding of a topic they can engage others in conversation, which has a domino effect and can quickly spread to colleagues and leaders.
Elevating the overall level of design discussion in an organization can effect future decisions around design such as the adoption of creative, development and programming pipelines, staffing/hiring decisions, work prioritization and goals creation.
2. The most successful designs are those that have the voice of the designer behind them.
It is not enough to put up boards (or screens) showcasing a visual presentation with no narrative in support of the effort. Designers need to be able to show not only what a given set of creative is, but also how it works and why it should work in the way they are proposing.
Questions abound in critique such as: What interaction is the design helping to accomplish, what research was used to inform the design decisions, how does it align with the company's goals, how does it move the brand forward? In my experience, a designer's inability to competently answer these kinds of questions detract from the value of the design, and can hinder adoption of the proposed creative.
I believe that this is especially true when you go beyond strict visual communication and start exploring elements of usability and human interaction (often grouped together in the field of experience design) or animation. Experience design requires that a designer be able to do more than communicate visually, because often the visuals cannot accurately convey the dynamic interaction that is at play between a design and its intended audience. With animation you are often using storyboards or animatics to convey the narrative initially, and such tools rely on verbal presentation to fill in the gaps that are not being fully conveyed with static frames.
A designer's voice should be an amalgam of visual and verbal communication that successfully advances creative solutions to problems and addresses use, usefulness and intent. Only then are we supporting our audiences and clients, and truly enhancing our profession.