Apple recently released what appears to be the final version (RC) of iOS 16.4. Among the key features, besides a new set of emoji, I would say that the most important are voice isolation si Safari push notifications.
After it was launched two days ago iOS 16.4 RC (Release Candidate) for developers, yesterday it was the turn of users with devices enrolled in Public Beta. Most likely, on March 28 it will be officially launched for all users of iPhone compatible iOS 16.
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Voice Isolation on iPhone, in iOS 16.4
iPhone with iOS 16.4 will soon have the ability to filter background (ambient) noises during calls over the cellular network. Characteristic Voice Isolation was introduced by Apple since last year for calls made via Face Time.
Voice isolation makes the voice heard more clearly during calls, eliminating much of the background sounds. Very important when you are in crowded areas or in environments with a lot of noise.

Safari Push Notifications in Home Screen si Lock Screen
With iOS 16.4, Apple offers users the possibility to receive notifications from web applications opened in Safari.
Safari push notifications will be available for those websites where web developers will implement this notification system for iOS.
Notifications will be present in Lock Screen pe iPhone, when the site you subscribed to has published new content, in Home Screen in the form of a badge in the Safari application and in the Notification Center.
This feature will also be present on iPad, with iPadOS 16.4.
Currently, the push notification system is only available on macOS.
Besides these new features, which I think are the most important, in iOS 16.4 adds a set of 21 new emoji and other features.