This paper presents experiments and results relative to a pitch determination of speech signals based on the "Narrowed" Autocorrelation Function (NACF), recently introduced by Brown and Puckette [1], It is shown that a reliable pitch estimation can be obtained even in a very noisy environment. An advantage of the NACF is that no preprocessing is needed before performing the pitch detection task. Also, a simple post-processing technique is sufficient to recover from the rare, isolated gross pitch errors that may occur. Finally, the paper proposes a short-cut in the computation of the NACF and it is shown that the number of multiplications can be drastically reduced. Keywords: Pitch, Narrowed autocorrelation