Today, I had to join around 20 .wav audio files into one. I have downloaded few free software and tested. The best one I have chosen is All Free mp3 Joiner with lots of options. It can convert files between various formats. Even, you can merge audio files of various formats and convert them into one format at a click. It can export the files into .wav, .ogg, .mp3, .wma. You can also change channels, sample rate, and bit depth. You can drag the files up or down to rearrange the order.