Androidがデフォルトの通話音量を変更

Android  6.0
AudioSystem.java

/* M: modify the default stream volume */  
    public static int[] DEFAULT_STREAM_VOLUME = new int[] {  
        4,  // STREAM_VOICE_CALL  
        15,  // STREAM_SYSTEM  
        8,  // STREAM_RING  
        8, // STREAM_MUSIC  
        8,  // STREAM_ALARM  
        8,  // STREAM_NOTIFICATION  
        7,  // STREAM_BLUETOOTH_SCO  
        15,  // STREAM_SYSTEM_ENFORCED  
        11, // STREAM_DTMF  
        11  // STREAM_TTS  
    };  

通話音量MAX値
AudioServer.java

/** Maximum volume index values for audio streams */  
    /// M: Modify the max stream volume   
    private static int[] MAX_STREAM_VOLUME = new int[] {  
        7,  // STREAM_VOICE_CALL  
        15,  // STREAM_SYSTEM  
        15,  // STREAM_RING  
        15, // STREAM_MUSIC  
        15,  // STREAM_ALARM  
        15,  // STREAM_NOTIFICATION  
        15, // STREAM_BLUETOOTH_SCO  
        15,  // STREAM_SYSTEM_ENFORCED  
        15, // STREAM_DTMF  
        15  // STREAM_TTS  
    };