Heart rate variability (HRV) is an extended tool to analyse the mechanisms controlling the cardiovascular system. It is assuming the integral pulse frequency modulation model (IPFM) to explain the beat occurrence times generation. Spectral estimate methods try to infer the modulating signal characteristics from the available beat timing on the ECG signal. These methods usually estimate the spectrum through the heart period (HP) or the heart rate (HR) signals. In this work, the authors introduce a new HRV signal, the Heart Timing Signal, (HT) that allows one to recover an unbiased estimate of the modulating signal spectra avoiding the spurious components produced when analysing the modulating signal through HR or HP.