Enhanced density fluctuations associated with the rational q = 2 (ł = 0.5) surface have been observed by microwave reflectometry in currentless discharges heated by neutral beam injection, with pellet injection at an edge value of the rotational transform ł of 0.52. A radial scan of the MHD activity located the coherent density fluctuations at r/a = 0.7. The frequency and amplitude of these fluctuations have been estimated. The correlation between the level of the local density fluctuation and the ł value during ł modulation at 300 Hz leads to the conclusion that the broadband density fluctuation is enhanced at the points where the rational ł values are crossed. A phase jump in the turbulence modulation occurs for r/a = 0.7, indicating the location of the resonant ł = 0.5 surface. This effect can become the basis of a new method to analyse the evolution of the ł profile inside the plasma, with interesting applications to current control experiments, especially in low shear configurations.