Noise & Vibration Capture with GPS Tracking

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The latest version of the CAN-bus/GPS (8440) module is now available for the Prosig P8012, P8020 and P8048 systems. The CAN-bus/GPS module has been in use in the field for some time now, recording CAN-bus information for display and analysis alongside noise, vibration, temperature and other signals captured by P8000 systems. The DATS software treats all analog and CAN-bus parameters in the same way so any mixture of parameters can be selected for display in real-time and subsequent processing. CAN-bus parameters can also be used to trigger immediate and pre-triggered captures and to stop captures.

The 8440 module now has an option to capture GPS parameters in addition to the other signals. The data capture software now also supports a realtime GPS track overlayed on a map. Velocity and altitude data measured by the GPS system can also be displayed alongside any other measurement channels in realtime displays. The latitude, longitude, altitude and velocity data is  stored with with all the other sensor data captured by the P8000 system and is available to view and process in the resulting datasets. These signals can then be used to classify or select data for further analysis. For example you could choose to process data when the vehicle is on a particular road or a particular section of the track, or if you find an unusual event use the GPS data to give a position and time or the event.

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Comparison Between Sound Intensity Probes and Acoustic Cameras

Sometimes 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 straightforward answer as they are quite different pieces of equipment, used for measuring different things. An acoustic camera is a tool used to locate and analyse sound sources, usually both steadystate and dynamic phenomena. The intensity probe is used to find the sound intensity at a particular position, usually a steadystate phenomena.

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Read more about the article 10 Great Fourier Transform Links

10 Great Fourier Transform Links

Joseph Fourier

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 great resources on Fourier and his work. So rather than keep all of the information to ourselves we thought we should share it with our readers. We have whittled our list down to 10 links that we think represent the whole range of information from beginners guides to reference pages. So there should be something for everyone whether you’re a grizzled signal processing veteran or a student looking to learn something new. If you have your own favourite Fourier links then please add them to the comments. Maybe we could use them for a future blog post. Or if you have other comments please feel free to add them below.

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Read more about the article Measuring For Success With A Hammer Impact Test

Measuring For Success With A Hammer Impact Test

The following application note shows the steps taken to perform structural analysis using a hammer impact test on an automotive exhaust pipe structure to improve the structural damping properties of the exhaust pipe mount. This application note follows up to a previous article – “Preventing Component Failure In The Fast Lane”.

A recent signal processing application note described how the Prosig sponsored Dalmeny Racing Formula Ford Team, whilst contesting the UK Formula Ford 1600cc championship, suffered several minor structural failures on a particular part of an exhaust pipe mount. Prosig dispatched a team of engineers, and after a brief survey of the damage, the engineers made an outline assessment. They concluded that “the exhaust itself is resonating at particular engine speeds. This is causing some shear forces in the mount. This in turn is causing stresses in the material leading to cracking and eventually failure.”

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Read more about the article Measuring Exhaust Noise Using A P8000 System

Measuring Exhaust Noise Using A P8000 System

The following note describes measuring exhaust noise using a Prosig P8000/DATS system for the refinement of an automotive muffler design for a major after-market exhaust manufacturer in Europe. The particular vehicle under test was required by local legislation to have an overall radiated noise level of less than 70 dB. When tested, the vehicle was found to be producing 71.8 dB of radiated noise. The design of the exhaust system clearly needed to be reviewed and modified. (more…)

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Read more about the article A Simple Automotive Noise Test

A Simple Automotive Noise Test

In 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 Formula Ford racing car. Whilst the car was instrumented for structural tests on the exhaust the opportunity was taken to carry out a simple automotive noise test. It was felt that these would provide some useful “real world” data as well as maybe providing some extra information regarding the exhaust bracket failure. After analysing and animating the hammer data it became clear that the engine runup data wouldn’t be needed. However, it was decided that some analysis should be carried out to see if the noise and vibration data backed up the conclusions of the other tests.

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Read more about the article Audio Equalisation Filter & Parametric Filtering

Audio Equalisation Filter & Parametric Filtering

When working with audio signals a common requirement is to be able to equalise, cut or boost various frequency bands. A large number of hardware devices on the market provide this capability. The key aspect is that such filters are able to control bandwidth, centre frequency and gain separately. There are broadly two classes of filter used, a “shelving” filter and an “equalising “filter (also known as a “peak” filter). A shelving filter is akin to low pass and high pass filters. An equalising filter is like a bandpass or band reject filter.

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Read more about the article A Weighting. And B. And C.

A Weighting. And B. And C.

Some devices, particularly digital tape recorders, apply A-weighting to all their data to achieve acceptable data compression. This is fine unless you want to analyse the unweighted data or apply a different weighting factor. Using Prosig’s DATS software, it is a simple task to instruct the WEIGHT module to either unweight the data or remove one weighting factor and apply another.

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Read more about the article Understanding The Cross Correlation Function

Understanding The Cross Correlation Function

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 some unknown position between 2 microphones. A cross correlation technique and a transfer function like approach were used to determine the location. (more…)

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Read more about the article Time Varying Overall Level Vibration (or Noise)

Time Varying Overall Level Vibration (or Noise)

A common requirement to measure overall level vibration (or noise) as a function of time. Now, the overall level is a measure of the total dynamic energy in the signal. That is it does not contain the energy due to the DC level, which is the same as the mean value. The overall level is often loosely referred to as the signal RMS value. However the formal definition of the RMS level is that it contains the DC level as well as the dynamic energy level. If only the dynamic contribution is required then the measure needed is, strictly speaking, the Standard Deviation (SD). Sometimes it is useful to refer to the SD as the Dynamic RMS.

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Read more about the article Interpretation of the Articulation Index

Interpretation of the Articulation Index

The Articulation Index or AI gives a measure of the intelligibility of hearing speech in a given noise environment. The metric was originally developed in 1949 in order to give a single value that categorised the speech intelligibility of a communication system. The basic interpretation of the AI value is the higher the value then the easier it is to hear the spoken word. The AI value is expressed either as a factor in the range zero to unity or as a percentage.

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