For the 12 months ending September 2018, unit sales of voice-enabled speakers increased 36 percent compared to the same timeframe year ago, according to The NPD Group's new Streaming Audio Speaker Total Market Report.

Dollar sales over the same timeframe increased 15 percent year over year, totaling $2.7 billion in the U.S.

While consumers are steadily adopting voice technology, many are choosing to enter the market at lower price points. During the 12 months ending September, voice-enabled speakers priced under $100 held 76 percent of the market based on unit sales, and slightly less than half the market based on dollar sales (44 percent).

Amazon and Google remain the two top-selling voice-enabled speaker brands, with more than three-quarters of U.S. unit sales combined, but new additions to the market are working to appeal to consumers who are looking for superior sound quality and are willing to spend more for it. In the 12 months ending September, voice-enabled speakers priced between $200 and $400 made up 5 percent of unit sales. The following brands are the top four in the industry in voice-enabled speaker unit sales: