Embedded Recording — Tiny, low-power audio solutions for wireless systems

The aim of this thesis was to explore and evaluate current methods for building tiny, low-power audio recording systems for wireless applications. Short audio clips should be recorded, transferred to a smartphone and played back. Optimization of the different parts should be explored and a prototype for usage in battery powered devices with limited space should be built. System requirements were defined in terms of audio quality, physical size and energy consumption. Additionally, the price should be kept low and the system should be reliable and stable, without notable delays. The system was divided into six focus areas; microphones, preamplifiers, signal processing, transmission, software design and energy consumption feedback. Each of those was explored theoretically and by practical prototyping, testing and tuning. Low energy consumption mainly proved to compromise audio quality, system speed and development time. Signal processing and transmission, especially range, speed and protocol overhead, played major roles. Size constraints did not affect performance very much, except for reduced battery capacity and microphone positioning options. Decent sound quality could be achieved with small size and low cost and signal processing could do much to keep energy consumption down and the perceived sound quality up