Audio is a beautiful medium for experimenting with real-world digital transmission. The necessary devices are cheap, everybody has a feeling what sound is and one can literally hear how your signal is being sent.
Though, to ensure you do not accidentally damage your built-in PC soundcard, it's recommended to use a dedicated external device. Below I present the hardware I am using and which works satisfactory:
I use a cheap (appr. $8) external USB soundcard from Sabrent.
For the speakers, I chose standard speakers from Amazon such as the /rewrite/Logitech Z120.
I selected a simple microphone. I did not care about the technical specifications, as more or less any will suffice.
In addition to transmission via speaker and microphone, I prefer to use a loopback cable between Line out and Mic in of the soundcard, such that I am not constantly exposed to the (actually quite annoying) sound of the transmission.