To get into the specifics, the new update will increase the maximum bitrate of 5.1 audio to 640Kbps, while a Dolby Atmos-supported show will increase to 768Kbps. For Netflix subscribers streaming over less than optimal internet speeds, the bitrate quality will drop to as low as 192Kbps. So as not to hinder the video’s buffer time. The good news is that 192Kbps is the floor cap, meaning that the audio quality will never deteriorate further than that. As impressive as the update may sound to audiophiles and Netflix subscribers, it is important to note that there is still a lot of audio compression. Especially when it is compared to an audio frequency running at 24-bit/48KHz.
As to why Netflix chose to set the audio bitrates limit at the new limit and not higher; the company believes the new bitrate samples are indistinguishable from lossless master tracks. Therefore, it sees to benefit to increase the bitrate sample to anything beyond 650Kbps and 768Kbps. (Source: Netflix Blog via The Verge)
