Sounds very interesting and helpful! Thanks for sharing leonheard.
PCM stands for Pulse Coded Modulation.PCM is uncompressed sound data.Each sample's amplitude is measured and stored as a number. Pulse-code modulation (PCM) is a method used to digitally represent sampled analog signals. It is the standard form of digital audio in computers, Compact Discs, digital telephony and other digital audio applications.
If u need more info watch youtube video on it www.youtube.com/watch?v=YJmUkNTBa8s
If you want to calculated Pulse Coded Modulation or Impedance then use this Engineering Tools. About 38kHz Just now i check it in this online software.http://actpcb.com/pcb-calculator
If u need more information about PCM email me. Helpful link For New engineers.