Due to the volume limitations, small loudspeakers cannot appropriately reproduce the lower frequencies that conform bass and percussive components in music. A virtual bass system tricks the human auditory system to create the impression of bass perception, even though the bass frequencies are highly attenuated, or not even physically reproduced. These methods make use of the missing fundamental effect, being able to psychoacoustically extend the low-frequency bandwidth of the signal by adding higher harmonics. It is still a challenge for a virtual bass system to induce the desired effect without deteriorating the audio quality. In the literature, virtual bass systems are implemented either in the time domain, with non-linear processing, or in the frequency domain, by using a phase vocoder algorithm. Hybrid systems separate the original signal into transient and steady-state sounds and process them separately, combining the strengths of both time and frequency domain techniques. This thesis proposes a novel hybrid method based on the fuzzy separation of transients, tones, and also noisy components. It introduces an improved phase vocoder based methodology, which intends to preserve as much as possible the original timbre of the signal. A conducted listening test shows that the proposed method outperforms selected previous algorithms. Moreover, another subjective experiment indicates that, by just processing three harmonics, the algorithm can effectively enhance the bass perception of small loudspeakers without significantly altering the audio quality
