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how to mute microphone in android by java programming

I am working on project that needs to mute the android microphone to avoiding record audio by any other apps.
I'm trying to googling and i found how to mute microphone but the articles just mute the microphone on during a call
code :
AudioManager audM = (AudioManager) m_instance.getSystemService(Context.AUDIO_SERVICE);
audM.setMicrophoneMute(true);
I need an article to mute the microphone on device that other apps can not record at all.
please help me to do that

Android AudioManager, provides all methods needed to play with mic. but your question has to do with a "global" hardware setup - not inside your app - so if Android OS does not provide that functionality, I think the only think you can do is directly blocking the mic to other apps, or block other apps while your code executes .. did you search APIs that does that ?
As for below thread, it seems that if your app initializes the mic, it wont be available for other apps to use it, I didn't check that.
Here is the thread:
How to block the mic for another app to use?

Why it is not possible to play an audio file on a voice call in android

This question might seem to be a repetition of the questions such as following:
How to play an audio file on a voice call in android
Background Audio for a Call in Progress - Possible?
The answers of these questions suggests that it is not possible to play a pre-recorded audio on a voice call in android. I want to know why it is not possible? What is the limitation (hardware/software)? Is it really a limitation or done purposely? Can we alter the source code of android to make it possible?

I think this is a limitation, imposed for security reasons and restricted at the OS level.
Let's analyze the security threat, first of all. If you were able to play custom audio files to the callee, a whole world of cons opens up: you could trick customer supports, you could pretend to be someone else, you could give unauthorized purchase confirmations, and so on. For this reason, neither Android nor iOS allows this functionality.
On Android, you won't be able to do so in a programmatic way, simply because the current APIs won't allow you to do so. It is stated in the official documentation as well, as pointed out here. If you dig into the source code, you can probably enable this feature by accessing the microphone output during a phone call, but that would require running your custom version of Android. A good starting point would be the AudioTrack source, available here.
EDIT: a good example of an audio mod involves enabling the Nexus 5 earpiece as a second loudspeaker (requires root). Can be found here.

After a thorough research, what I have come to know is that there are more than one limitations/hurdles to make it possible. These limitations/hurdles are at three different levels.
First limitation is at API level, because there is no high-level API to play sound files in the conversation audio during a call as mentioned in Android official documentation.
Second limitation is at Radio Interface Layer (RIL). RIL passes on complete control of the call to Radio Daemon (rild) of the Linux library which then further passes the control to the vendor RIL. That means we cannot manipulate voice call in android source code.
Even if we are able to remove these two limitations, we may still not be able to play audio file to an ongoing voice call. Because there is a third limitation. Every vendor has their own library of RIL that communicates with Radio Daemon (rild). This requires that vendor RIL to be open source which is not actually. Hardware vendors do not usually make their device drivers code available.
Detail discussion on this topic is present at this link.

This is software related due to the prioritization of audio routing in Android.
Take a look into the CallManager where you can dig into the method setAudioMode(). After the audio mode was set to MODE_IN_COMMUNICATION the following code is called
audioManager.requestAudioFocusForCall(AudioManager.STREAM_VOICE_CALL,
AudioManager.AUDIOFOCUS_GAIN_TRANSIENT);
From this point on the telephony service has the highest priority and won't let any other audio play in parallel.

Note: You can play back the audio data only to the standard output device. Currently, that is the mobile device speaker or a Bluetooth headset. You cannot play sound files in the conversation audio during a call.
See official link
http://developer.android.com/guide/topics/media/mediaplayer.html

By implementing the AudioManager.OnAudioFocusChangeListener you can get the state of the audiomanager. so by this if any music is playing in the background you can get the AudioManager states(playing and pausing is completely in developer hands) similarly......
Some of the native music players in android device where handling this, they restrict the music when call is in TelephonyManager.EXTRA_STATE_OFFHOOK.so this scenario is also completely in developer hand (whether to handle or not) if he is not handling both will play parallel y

How android call recorders apps works?

There are plenty apps in google play, which can record calls. Some of them just turn on loudspeaker and record sound via microphone, others should be able to record audio steams directly. I know that android provides class for recording. (which doesn't work on lot of devices probably because of some SW restrictions).
So here is my question: Is there possibility to find some device, where call recording will be possible via MediaRecorder(VOICE_CALL)? I found that call recording apps are available for Galaxy SII and SIII so does it means that MediaRecorder(VOICE_CALL) work on these devices?
EDIT------------
Generally, if i want to use MediaRecorder to record calls i need kernel which supports it (for example som custom kernel)?

Is there any equivalent function of requestAudioFocus in Android API level 7?

My Android application needs to support Android platform 2.1.x (which is Android API level 7). I need to use requestAudioFocus() and abandonAudioFocus() methods to pause other applications (e.g. Music) to play when my application starts playing media and resume them after my application stops.
However, these two functions are only available at API Level 8 and above. What are the equivalent functions at API level 7? Or how to do this before API level 8?

Thanks to Christopher (http://stackoverflow.com/questions/1993471/android-can-i-mute-currently-playing-audio-applications), I am citating:
Audio handling on Android is going to be pretty horrible for a while. The APIs are pretty weird, poorly documented, and keep changing/deprecating/breaking between versions. Even the AudioManager code has FIXMEs in it.
Anyway, there are several stream types in Android (music, notifications, phone calls, etc.) and applications are meant to choose the appropriate one for playback. I imagine the majority of Android apps should use the music/media type (STREAM_TYPE_MUSIC). You set this on your MediaPlayer using the setAudioStreamType method.
The SDK does allow you to set a single stream type as solo — causing all other streams to be muted — but I don't believe you can identify the audio being played back by particular applications and somehow pause/unpause it. Music applications in general will use the PhoneStateListener to pause themselves when a call comes in.
So in your case, you could "borrow" the phone call stream for your MediaPlayer and use the method call AudioManager.setStreamSolo(AudioManager.STREAM_VOICE_CALL, true) when playback begins, then un-solo the stream with false when playback or your Activity is done.
I can tell you that this works, but I can't remember offhand whether you need to also set the audio mode to MODE_IN_CALL when using the voice call stream (like this: AudioManager.setMode(AudioManager.MODE_IN_CALL)). If you find that is required, then you need to make sure you return the mode to MODE_NORMAL once playback completes, otherwise whenever you press the volume hard keys, it'll say "In-call volume"! However, if and when you do want to change back to MODE_NORMAL, you must check that a genuine phone call isn't happening at that time...
Maybe you could use another stream type rather than the voice call one, but I'm just speaking from experience working on an app that could use either the speakerphone or the earpiece for audio playback, which requires the use of the voice call stream.
Like I said, audio handling isn't particularly fun... ;)

Android: Manipulating voice in phone calls

I'm currently searching for options on how to manipulate audio on android. The goal is to process audio from the microphone in real time during a phone call. The best solution would be to do this on a native call. But rebuilding a telephone app (no VOIP) would be fine too. Are there any ways to achieve this with Android APIs (also undocumented)?
If not, which steps would be necessary to get things running?
On iOS there are some apps which manipulate voice but create a VOIP connection. I heard that on Android you can "clone" the telephone app and eventually feed it with your own audio stream? Aren't there apps which add noises during a call? What kind of APIs are involved?

The best solution would be to do this on a native call.
This is not possible. You have no access to the in-call audio stream, except perhaps in speakerphone mode.
But rebuilding a telephone app (no VOIP) would be fine too.
The last official word from Google (2010), the entire OS has no access to the in-call audio stream, as it is all handled at a lower level. Even if newer versions of Android do have access to the in-call audio stream, "rebuilding a telephone app" is only possible if you are creating custom firmware.

As a drawback i could imagine to record the Downlink Stream using the MediaRecorder API and write it back to hardware using AudioTracks write() method. By this i could manipulate incoming voice. But still I think this wont work during phone calls. And I do not see a way to choose different hardware destinations.