AI share of voice
AI share of voice is the share of sampled AI answers that name one brand, out of the answers that name any tracked brand (that brand or a competitor it tracks), across a fixed set of category questions. It counts presence per answer, not raw mention counts. If 400 sampled answers named at least one tracked brand and 100 of them named yours, your share of voice is 25 percent.
The formula
Answers that name you, divided by answers that name at least one tracked brand (you or a competitor you track), computed per engine and overall. An answer counts once per brand, however often it repeats the name, so the shares of all tracked brands can add up to more than 100 percent. It puts you and your competitors on the same scale, which is why it is the headline metric and why it needs visibility rate next to it. Some tools count raw mentions instead, so numbers differ between tools.
Where it misleads
It is relative, so it rises when a rival drops out of answers that named no other tracked brand, even if you are named no more often. It swings on small samples, so it needs a sample-size floor. It depends on the competitors you track, because an answer that names only untracked brands does not count. And it depends entirely on the prompt set, so the set must stay fixed while periods are compared.