Share of voice in digital marketing is the share of exposure a brand gets by weight or percentage among other advertisers.
Share of Voice in Online Advertising is an ad revenue model that focuses on weight or percentage among other advertisers. For example, if there are four advertisers on a website, each advertiser gets 25 percent of the advertising weight. This method ensures one ad will not be seen by any more than the other three advertisers. And, since there are typically a limited number of advertisers using a Share of Voice model, ad exposure is optimized.
In other words, Share of Voice is used to "represent the relative portion of ad inventory available to a single advertiser within a defined market over a specified time period."