A method for attenuating pump noise in a wellbore drilling telemetry system includes spectrally analyzing measurements of a parameter related to operation of a pump used to move drilling fluid through the drilling system. Synthetic spectra of the parameter are generated based on a number of pumps in the pump system and a selected number of harmonic frequencies for each pump. Which of the synthetic spectra most closely matches the spectrally analyzed parameter output is determined. The most closely matching synthetic spectrum is used to reduce noise in a signal detected proximate the Earth's surface transmitted from a part of the drilling system disposed in a wellbore.