Tag: FFT

Sometimes it doesn’t hurt to revisit some of the basic building blocks that form the foundation of what we do. And so we have gathered together a few

This post covers how to upsample and downsample data and the possible pitfalls of this process. Before we cover the technical details let us first explain what we mean

Are you attending the SAE 2015 Noise and Vibration Conference and Exhibition in Grand Rapids, Michigan, USA from 22nd to 25th June 2015? Why not go and see Dr

The RMS of a time history is a measure of the signal’s overall energy and is often used when extracting features from a signal for prognosis and trending

The term synchronous data is usually applied to vibration or acoustic data that is captured from an item of rotating equipment at regularly spaced angle intervals as distinct

This is complete version of the video illustrating my recent article How To Measure Noise & Vibration In Rotating Machines. This video was previously published on the blog in

[latexpage]The following article was inspired by a question asked by a reader regarding my previous article – Data Windows : What, why and when?. Specifically, the reader asked “Could

Amplitude and energy correction has been and is a continuing point of confusion for many people calculating spectra from time domain signals using Fourier transform methods. The first

Before we discuss the use of data windows, we should first remind ourselves of three basic properties of the FFT (Fast Fourier Transform) process. First, energy information in

Following a discussion in the office about Fourier Transforms we did a little searching on the web. As always, we discovered that the Internet is packed with some

The requirement was to develop a ‘standard’ test for assessing power steering pump noise (and sound quality) in vehicles. Measurements needed to be objective so that the method

Order cuts are taken from a set of FFTs, each one at a different rpm. The rms level is then found as the Square root of the Sum

[latexpage]One would expect that averaging waterfalls and then extracting orders would give the same result as extracting orders from individual waterfalls and then averaging them. This is not

A Fourier Transform takes a signal and represents it either as a series of cosines (real part) and sines (imaginary part) or as a cosine with phase (modulus

The most common form of digitising data is to use a regular time based method. That is data is sampled at a constant rate specified as a number

To illustrate the use of the cross correlation function, a source location example is shown below. For this, it is assumed that there is a noise source at

Sometimes we have digitised data at a much higher rate than we need. How can we downsample data? If I wanted to say halve the sample rate can