Sound capture in CPP and Qt

Qt 4.6 introduces a new, low level suite of audio APIs in the QtMultimedia module. You can use QAudioInput to capture raw audio from a microphone.

At present, this API is implemented for Windows, Mac, and Linux (supporting PULSE and ALSA audio subsystems). Support for other platforms, including Symbian in the mobile space, is currently under development.

OpenAL is a good, cross-platform C++ library for capturing audio.