We present experimental results that show that the scale-factor relating the formant frequencies of different speakers increases with decreasing values of formant frequency. Based on these results, we experimentally obtain a frequency warping function aimed at separating speaker dependencies from the inherent characterization of the sound. We find that the frequency warping function is similar to the Mel scale, and we believe that this is the first time that a Mel-like scale has been obtained using only speech. Our results and methods may therefore explain, from a speech point of view, the Mel scale, which was obtained historically from hearing based experiments.