A method and system for detecting certain types of content, such as advertisements, using acoustical means from a media stream. The method uses two matching processes to detect and identify repeated content, the starting and end boundaries of which are then found. This content is used as the basis to find non-repeated content (such as less-frequently repeated advertisements) that are typically located in proximity to repeated content and can be evaluated using Gaussian mixture models (GMMs). The system that implements this method can be used for advertisement detection and monitoring for traditional media, such as television and radio, as well as for Internet-based media, such as streaming video, streaming audio and podcasts. The system can also be used to detect and identify copyrighted material in Internet traffic.