Audio fingerprint is a compact unique content-based digital signature of an audio signal. It's an interesting technique that can be used to identify unknown audio clips. Generally, it mainly consists of two parts, i.e. fingerprint extracting from audio signals and fingerprint matching against those stored in a fingerprint database that has been set up beforehand. With the rapid growth in the quantity of audio files, the probability of collision of different audio signals become relatively high and it has become very challenging to retrieve an audio recording in real-time from the ever-growing huge database. In this letter, we introduce a reliable audio fingerprinting system, which extracts audio fingerprints from an audio signal based on its spectral energy structure. Preliminary experimental results suggest that this fingerprinting system can work well in the application of broadcast monitoring. (4 pages)