nvh Archive
Developing an Algorithm for Tick Detection
Posted on August 23, 2010 | 3 CommentsAn investigation was made of a sample of automotive components where some were exhibiting a high frequency “tick” or rattle during each operating cycle. This feature could be heard above...
Removing A-Weighting From Time History Signals
Posted on July 22, 2010 | No CommentsIt sometimes occurs that signals are captured with A-weighting applied to the data by the acquisition device. This can be a problem if, for example, you wish to use the...
Prosig Announce New Braking Analysis Tools
Posted on July 5, 2010 | No CommentsProsig are pleased to announce the launch of two new tools to assist engineers in the measurement and analysis of noise and vibration issues in braking systems. Controlling noise and...
Aliasing, Orders and Wagon Wheels
Posted on June 29, 2010 | No CommentsThese days most people collecting engineering and scientific data digitally have heard of and know of the implications of the sample rate and the highest observable frequency in order to...
The Causes of Road Noise
Posted on March 30, 2010 | 1 CommentRoad noise (the noise produced by the interaction of tires and road surface) is in many circumstances the dominant noise experienced by vehicle occupants. The requirements for producing quieter roads...
Comparison Between Sound Intensity Probes and Acoustic Cameras
Posted on March 15, 2010 | 4 CommentsSometimes we are asked about the differences between an acoustic camera and a sound intensity probe and which of the two is better for a particular application. There is no...
A Simple Frequency Response Function
Posted on October 19, 2009 | 20 CommentsThe following article will attempt to explain the basic theory of the frequency response function. This basic theory will then be used to calculate the frequency response function between two...
Amplitude And Energy Correction – A Brief Summary
Posted on September 1, 2009 | 8 CommentsAmplitude 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 thing to...
Data Windows : What, why and when?
Posted on July 20, 2009 | 7 CommentsBefore 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 signal must...
Measurement And Analysis Of Torsional Vibration
Posted on October 17, 2008 | 13 CommentsTorsional vibration is of key importance in the area of vehicle development and refinement. The main contributory source is the engine where periodically occurring combustion cycles cause variation in the...
Orders v Time – Comparing Overall Levels
Posted on October 23, 2007 | 4 CommentsBy combining a speed signal with a data signal and using the Short Time FFT algorithm (Hopping FFT), it is possible to extract order data directly as a function of...
Sound Steering
Posted on September 12, 2007 | No CommentsThe requirement was to develop a ‘standard’ test for assessing the sound quality of power steering pumps in vehicles. Measurements needed to be objective so that the method would be...Measuring Torsional Crank Shaft Jitter
Posted on June 24, 2007 | No CommentsUsing Prosig’s P8000 series data acquisition system with DATS signal analysis software, torsional analysis (crank jitter) was performed on an automotive engine attached to an engine dynamometer. The significance of...
What Is Resonance?
Posted on May 23, 2007 | 21 CommentsFirst, in order to explain resonance we have to explain the terms we will use. - A resonance is a particular frequency. - A period is the amount of time...Order Cuts And Overall Level
Posted on February 25, 2007 | No CommentsOrder 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 of the...
Acceleration, Velocity & Displacement Spectra – Omega Arithmetic
Posted on December 7, 2006 | 18 CommentsAccelerometers are robust, simple to use and readily available transducers. Measuring velocity and displacement directly is not simple. In a laboratory test rig we could use one of the modern...
Measuring For Success
Posted on September 11, 2006 | No CommentsThe following application note shows the steps taken to perform a structural analysis on an automotive exhaust pipe structure with the aim of improving the structural damping properties of the...
Exhaust Development Using A Prosig P8000 System
Posted on February 20, 2006 | 2 CommentsThe following note describes an application of the Prosig P8000/DATS system in the refinement of an automotive exhaust muffler design for a major after-market exhaust manufacturer in Europe. The particular...Torsional Vibration, Tacho Pulses And Aliasing
Posted on January 12, 2006 | 3 CommentsWith shafts, gears and the like, the general method of determining the rotational speed is to use some form of tachometer or shaft encoder. These give out a pulse at...A Simple Noise Test
Posted on August 26, 2005 | 2 CommentsIn a recent article we described how the Prosig P8000 hardware and DATS software had been used to help Dalmeny Racing diagnose a problem with an exhaust bracket on their...Average Waterfalls Or Average Orders?
Posted on June 14, 2005 | No CommentsOne 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 the case.
Smoothing Spectral Data
Posted on July 15, 2002 | No CommentsSometimes data has spikes which are clearly artefacts of the processing or are due to some other external source. One is used to seeing these on time series but in...
Measuring Torsional Twist & Vibration Along a Shaft or Through a Geartrain
Posted on May 15, 2002 | 3 CommentsThe measurement of the twist angle between two points along a shaft or through a gear train may be derived from a pair of tacho signals, one at each end...Dynamic Range And Overall Level : What Are They ?
Posted on June 7, 2001 | No CommentsAccurate measurement of a signal depends on the dynamic range and the overall level of the data acquisition system. The overall level setting may be thought of as determining the...
High Pass Filtering And Tacho Signals
Posted on June 6, 2001 | 2 CommentsIt is sometimes necessary to pass a signal through a high pass filter to eliminate low frequency signals. These may arise for instance from whole body vibrations when perhaps our...
