Digital forensics has become a flourishing research area. Electrical Network Frequency (ENF) plays an important role in assessing the authenticity of a digital recording such as audio. ENF criterion is a tool for extracting the embedded power line frequency from the recording. A cross correlation between a reference PMU data and extracted ENF signal can be done in order to determine the authenticity of an audio signal. In this paper, Empirical Wavelet Transform (EWT) is used for extracting the ENF from an audio signal. EWT decomposes signal into N modes. Hilbert Transform is used to compute the instantaneous frequency and amplitude of the extracted mode corresponding to ENF. EWT method is not able to capture the weak harmonics in a signal. This problem is resolved by fixing the frequency domain boundaries of each mode. (C) 2015 The Authors. Published by Elsevier Ltd.