We report the experimental study of noise in electrochemical biosensors as related to voltage and concentration. A comparison with experiments is performed for H₂O₂ and Ferrocyanide with bare sensors and with sensors functionalized with Multi-Walled Carbon Nanotubes (MWCNT) modified electrodes. Chronoamperometry measurements at different voltages were carried out, followed by fast Fourier transform analysis of noise at different concentration of analyte to understand the effect of concentration and voltage on the noise <i>Power Spectral Density</i> (PSD) and the <i>Signal over Noise</i> (SNR) ratio. Experimental results demonstrate the presence of 1/f noise and its dependence on the state variables. The parameters of 1/f noise i.e. the amplitude coefficient and frequency power coefficients are extracted by curve fitting, and are characterized by comparing the coefficient in different molecules, electrodes, voltages and concentration.