One of the first mainstream devices of its kind, Apple TV is a big seller worldwide. Apple has sold 25 million of the boxes in its lifetime, Chief Executive Tim Cook said in March. That beats Roku's 10 million total sold as of last year. Neither Google nor Amazon has released stats for their streaming devices, Chromecast and Fire TV, respectively.

However, Apple TV has been slipping. Last year, its US sales fell to fourth place behind Roku, Chromecast and Fire TV, according to estimates from market researcher Parks Associates. Strategy Analytics, another market researcher, similarly notes that for the first time, Apple sold fewer Apple TVs in the second quarter than it had a year earlier.

Last year, Parks Associates reported an even smaller percentage of streaming-media device owners who use voice controls, putting the number at about 4 percent. Barbara Kraus, director of research at the firm, noted that gaming consoles, not streaming-media devices, are the natural place for spoken commands to break out because video games are more interactive compared with the passive act of watching TV.

From the article "The next Apple TV puts company in rare role: Playing catch-up" by Joan E. Solsman.