Purpose: The goal of this study was to establish the perceptual underpinnings of the terms that are commonly used by patients when describing the quality of their tinnitus. Method: Using a free-classification method, 15 subjects with normal hearing placed 60 different tinnitus-like sounds into similarity clusters on a grid. Multidimensional scaling, hierarchical clustering, and acoustic analyses were used to determine the acoustic underpinnings of the perceptual dimensions and perceptual similarity. Results: Multidimensional scaling revealed three different perceptual dimensions (pitch, modulation depth + spectral elements, and envelope rate). Hierarchical clustering revealed five explicit similarity clusters: tonal, steady noise, pulsatile, low-frequency fluctuating noise, and high-frequency fluctuating. Conclusions: Results are consistent with tinnitus perceptions falling into a small set of categories that can be characterized by their acoustics. As a result, there is the potential to develop different tools to assess tinnitus using a variety of different sounds.