主要用到了MediaRecorder类，实现代码如下：

    MediaRecorder mRecorder = new MediaRecorder();  
            mRecorder.setAudioSource(MediaRecorder.AudioSource.MIC);  
            mRecorder.setOutputFormat(MediaRecorder.OutputFormat.THREE_GPP);  
              
            File dir = new File(Environment.getExternalStorageDirectory().getAbsolutePath(),"ivr_record");  
            if(!dir.exists()){  
                dir.mkdirs();  
            }  
              
            mFileName = new File(dir,"ivr_"+System.currentTimeMillis()+".3gp").getAbsolutePath();  
              
            Log.i(TAG, "start recording:"+mFileName);  
              
            mRecorder.setOutputFile(mFileName);  
            mRecorder.setAudioEncoder(MediaRecorder.AudioEncoder.AMR_NB);  
      
            try {  
                mRecorder.prepare();  
            } catch (IOException e) {  
                Log.e(TAG, "prepare() failed");  
            }  
      
            mRecorder.start();  

这种方式只能录自己的语音，对方的语音录不到，如果想录对方的语音，只需要将audio source设置成 MediaRecorder.AudioSource.VOICE_CALL就可以了，代码如下：

    MediaRecorder mRecorder = new MediaRecorder();  
            mRecorder.setAudioSource(MediaRecorder.AudioSource.VOICE_CALL);  
            mRecorder.setOutputFormat(MediaRecorder.OutputFormat.THREE_GPP);  
              
            File dir = new File(Environment.getExternalStorageDirectory().getAbsolutePath(),"ivr_record");  
            if(!dir.exists()){  
                dir.mkdirs();  
            }  
              
            mFileName = new File(dir,"ivr_"+System.currentTimeMillis()+".3gp").getAbsolutePath();  
              
            Log.i(TAG, "start recording:"+mFileName);  
              
            mRecorder.setOutputFile(mFileName);  
            mRecorder.setAudioEncoder(MediaRecorder.AudioEncoder.AMR_NB);  
      
            try {  
                mRecorder.prepare();  
            } catch (IOException e) {  
                Log.e(TAG, "prepare() failed");  
            }  
      
            mRecorder.start();