In this paper we discuss theory, system design and implementation of an acoustical communication system. We aim to transmit data from the bottom of a borehole to the surface with data rates of at least 200 bps. As a technical solution we use acoustic waveguide communication with adaptive OFDM over a baseband frequency spectrum from 0 to 9 kHz. We characterize hardware components and discuss how to deal with their non-linearities. Furthermore we estimate the signal-to-interference due to these non-linearities and adapt modulation and coding over frequency correspondingly. We evaluate the codeword error rate by link-level simulations based on 3GPP LTE specifications and estimate an upper bound for the achievable data rate.