Techniques for acoustic signal processing are driven by the demand for seamless acoustic interfaces for human-machine communication. For both signal reproduction and acquisition, the desired mobility of human users and the potentially noisy acoustic environment call for efficient methods of suppressing unwanted noise and enhancing desired signals, such as speech and music. While single-channel techniques usually require less processing power, their potential for suppressing noise and reverberation is limited. Multi-channel techniques involving beamforming exploit information for signal separation, and, therefore, are generally more efficient. This white paper discusses both methods and how the growing demand for seamless acoustic interfaces for multimedia and telecommunication terminals is driving the development of increasingly sophisticated concepts.