android - Androidでオーディオの周波数を増幅する方法やバックグラウンドノイズを減らす方法

Question

これは私のコードです

Thread Rthread = null;
AudioRecord record = null;
int freq = 8000;
AudioManager am;
AudioTrack play;
int minbuff=20000;
AudioRecord m_record;
AudioTrack m_track;
byte[] buffer = new byte[freq];

protected void Start() {
    Rthread = new Thread(new Runnable() {
        public void run() {
            loopback();
        }
    });
    Rthread.start();
}

protected void loopback() {
    android.os.Process.setThreadPriority(android.os.Process.THREAD_PRIORITY_URGENT_AUDIO);
    minbuff = AudioRecord.getMinBufferSize(freq,
    AudioFormat.CHANNEL_CONFIGURATION_MONO,
    AudioFormat.ENCODING_PCM_16BIT);
    if (minbuff <= freq) {
        minbuff = freq;
    }
    am.setParameters("noise_suppression=on");
    m_record = new AudioRecord(MediaRecorder.AudioSource.MIC, freq,
    AudioFormat.CHANNEL_CONFIGURATION_MONO,
    MediaRecorder.AudioEncoder.AMR_NB, minbuff);
    m_track = new AudioTrack(AudioManager.ROUTE_HEADSET, freq,
    AudioFormat.CHANNEL_CONFIGURATION_MONO,
    MediaRecorder.AudioEncoder.AMR_NB, minbuff,
    AudioTrack.MODE_STREAM);
    m_track.setPlaybackRate(freq);
    byte[] buffer = new byte[minbuff];
    m_record.startRecording();
    Log.i(LOG_TAG, "Audio Recording started");
    m_track.play();
    Log.i(LOG_TAG, "Audio Playing started");
    while (true) {
        try {
            m_record.read(buffer, 0, minbuff);
            for (int i = 1; i < buffer.length; i++) {
                buffer[i] *=amp;
            }
            m_track.write(buffer, 0, buffer.length);
            } catch (Throwable t) {
            Log.e("Error", "Read write failed");
            t.printStackTrace();
        }
    }
}

では、バックグラウンドノイズを減らし、録音されたオーディオの周波数を増幅する方法を教えてください。