This application has been implemented using the Qt framework, as a GUI application, so that we also get a graphical interface for ease of debugging. This debugging UI was designed using the Qt Designer of the Qt Creator IDE as a single UI file.
We start by creating an instance of the GUI application:
#include "mainwindow.h" 
#include <QApplication> 
 
int main(int argc, char *argv[]) { 
    QApplication a(argc, argv); 
    MainWindow w; 
    w.show(); 
     
    return a.exec(); 
} 
This creates an instance of the MainWindow class in which we have implemented the application, along with an instance of QApplication, which is a wrapper class used by the Qt framework.
Next, this is the MainWindow header:
#include <QMainWindow> 
 
#include <QAudioRecorder> 
#include <QAudioProbe> 
#include <QMediaPlayer> 
 
 
namespace Ui { 
   ...