Chromecast Audio has Wi-Fi connectivity and the ability to stream audio. It looks and works like a standard Google Chromecast, except that it transmits audio only via a spur line instead of an HDMI connection. The device was first used in 2015. release.
Since then, Google has released a number of smart speakers, including Google Home, Google Home Mini, Google Home Max and Google Home Hub.
You can now get from Google at $15 (or £30 / $59)websitePurchase a Chromecast Audio device. However, since the equipment has been discontinued, once the stock is exhausted, it can no longer be purchased.