Question: I have a very interesting problem.

I was under the impression that when my app uses the microphone, and the Android system process (like incoming or outgoing call) needs the microphone, my app releases it without any consideration.

But i guess that is not the issue anymore, since i have received few complains that when the app is being used and there is incoming call, the other side on the call, can not hear them.

Is there any way to assure that whenever system process requests the microphone, to be released?

Answer: 
Currently, **there is no way to check whether another app requests the microphone**. However, there are some workarounds:

* If you record sound in an Activity, simply release the microphone in `onPause()`, so that the foreground app can use it. This won't work if you record audio in a background service.
* Pause the recording when there is an incoming call. To detect incoming (and outgoing) calls, take a look at [this excellent answer](https://stackoverflow.com/a/15564021/2829009). When the call ends, resume the recording.
* A dirty hack: If detecting incoming calls isn't enough, you could loop through all running apps and see if they have the microphone permission. As soon as an app with microphone permission is running, pause the recording. Getting all running apps can be difficult. For more infos, look [here](https://stackoverflow.com/questions/30619349/android-5-1-1-and-above-getrunningappprocesses-returns-my-application-packag), [here](https://stackoverflow.com/questions/24590533/how-to-get-recent-tasks-on-android-l/26885469), [here](https://stackoverflow.com/questions/3873659/android-how-can-i-get-the-current-foreground-activity-from-a-service/27642535) and [here for checking the permissions](https://stackoverflow.com/questions/4461504/determine-list-of-permissions-used-by-an-installed-application-in-android).
As far as I know, **there is no way to know the microphone's state** is Busy, Available or **if somebody is requesting** for it because it's somehow these are responsibility of system to manage processes and resources so keeping this in mind , you can't keep the microphone forever and there so no way you can control it mean you can't mange and detect the request on resources .Following there is some info that might help you.

What you can try is , overcome the all possibilities when system can use microphone like setup a broadcast receiver for call broadcasts and when they triggered release the microphone and when call is done then you can acquire it again.