Allegro播放声音程序，就是不发声

用DJGPP+Allegro编写了一人简单的播放wav文件的程序，就是不发声，确信硬件工作正常（BC编写的声音播放程序正常），请各位大虾指点。
#include <allegro.h>
int main( void )
{
        SAMPLE *boing;
        allegro_init();
        install_keyboard();
        install_sound( DIGI_AUTODETECT,MIDI_AUTODETECT,NULL );
        boing = load_sample( "tada.wav" );
        if (boing!=NULL)
        {
             printf(" Playing \n");
             play_sample( boing,255,128,1000,0 );
                readkey();
                destroy_sample( boing );
        }
    else
        printf(" Error \n");
        return 0;
}
END_OF_MAIN()
运行程序显示  Playing