Much confusion revolves around linear and non-linear numbers. The following outlines the mathematical process to convert from a number expressed in dB to a linear quantity. How do we convert to decibels and back again? (more…)
How do you measure the causes of a noise or vibration with respect to several sources? Which source is causing what part of the response?
For example, how does the noise inside the cabin of a vehicle relate to the engine noise or wheel hub noise and vibration? (more…)
Here are two videos on a relatively simple, but sometimes misunderstood procedure – how to calibrate microphones & accelerometers (more…)
Here are two videos on a relatively simple, but sometimes misunderstood procedure – how to calibrate microphones & accelerometers (more…)
The objective of the brake noise tests was to record the braking events of cars being driven on various types of road and classify those events according to their type (Groan, Creep or Squeal etc) and severity. To do this the customer needed a system capable of working for long periods inside a vehicle in fairly tough conditions (high ambient temperatures, rough road) that was both quick to install and to remove.
On previous tests a system from another supplier had turned out to be unreliable and had failed to cope with the harsh environment. The analysis processing had also proved tedious and time consuming due to the huge amount of data created when testing several vehicles over many days.
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.
We're often asked what is the difference between microphone types; free field, diffuse field and pressure. For a run-of-the-mill ½ inch microphone the short answer is nothing. However the long…
The requirement was to develop a ‘standard’ test for assessing vehicle power steering pump noise (and sound quality). Measurements needed to be objective so that the method would be suitable…
[Updated 4th October 2021]
In this post, we will discuss the different types of transducers that can be used with the Prosig data acquisition systems and loggers. The post looks at the design and function of the different types of sensors and the applications they are normally associated with.
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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…)
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.
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…)
