DOI resolved by resea

The use of fast Fourier transform for the estimation of power spectra: A method based on time averaging over short, modified periodograms

The use of the fast Fourier transform in power spectrum analysis is described. Principal advantages of this method are a reduction in the number of computations and in required core storage…

P. D. Welch
https://resea.org/10.1109/tau.1967.1161901

Abstract

The use of the fast Fourier transform in power spectrum analysis is described. Principal advantages of this method are a reduction in the number of computations and in required core storage, and convenient application in nonstationarity tests. The method involves sectioning the record and averaging modified periodograms of the sections.