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Interesting article on this topic by Bruel & Kkaer. See link. http://www.bksv.com/NewsEvents/Waves/Waves_2014_1/07-guitar-evolution

As I said before, its a complex situation and not normally solved in a few days. Items 3 and 5 are related. In our mill we found that older work rolls were consistently involved when we had chatter. One solution was to use all newer work rolls when we had chatter. For some critical products...

Its been years since I did Chatter investigations on a 4 stand Cold Mill. There are many conditions which cause the mill to go into Chatter but it takes time and measurements to sort it out. Some observations and comments I have are: 1) Its interesting that the work rolls do not show chatter...

Not much information to work with so I have questions. Is the vibration problem on the compressor or is it the support beam? What is the overall vibration at the compressor? Higher or lower than the support beam? I agree with StrykerTech that frequency info is required. Taking a shot at...

Just a quick comment. Time Domain Analysis has been around a lot longer than a few years. It just had a different name but is the same thing. It was called the "Chart Recorder". You got amplitude versus time. Faster paper speed equals more resolution. Chart recorders were around long...

The basic equation is in "Noise and Vibration Control Engineering" by Beranek and Ver. A simplified form is below. Lp = Lw - 20 log (r) + DI -11 Lp = sound pressure level. Lw = sound power level r = distance from source to receiver DI = directivity index. Use 3 for free field (outdoors)...

The short answer to your question is Yes. You need to make/determine a few parameters. 1) Distance to the sound pressure level point, (usually 3 feet or 1 metre). 2) Is the measurement point indoors or outdoors. Most contracts just assume outdoor conditions or "free field conditions". i.e...

In the past where there are multiple degrees of freedom, I have used wire rope isolators. I used it in reverse to protect a computer system on a locmotive engine and also to isolate a fan system which was shaking a roof. See: http://www.enidine.com/Industrial/WireRopeIsolators.html Just make...

Do you mean specify or design. I don't see why you have to design a new louvre unless you are talking a new product. There are quite a few suppliers of off-the-shelf acoustical louvres out there which can also be made to fit. Most louvres are 6" to 12" deep and provide a maximum 12 dB...

Somptinguy, I looked up the solution for a Helmholtz resonator and the equation is: helmholtz resonance freq = v/2PI * sqrt (A/Vo L) The v in the equation is the speed of sound in a gas so do you have another equation where the speed of sound is not required?

Interesting Question here are my thoughts: 1) In my experience the noise comes from the vacuum pump itself and the motor. The pipe noise is not usually a problem. 2) OK assuming the pipe noise is an issue, the inlet pipe is operating in a vacuum. What speeed of sound do you use to design the...

The basics of silencer selection are as follows: Higher Insertion Loss = higher pressure drop. Longer Silencer = higher pressure drop. Higher low frequency performance = Longer Silencer Higher blockage = Higher velocities in silencer (passage velocity) Higher Passage Velocity = higher pressure...

A mil is a thousandth of an inch, (0.001 inches). Or... 1000 mils = 1 inch.

You don't mention the frequency(s) of the high vibration, which can provide a significant clue to your problem. However, I have seen the follwing items cause high to severe vibration: 1) Pump shaft runout. 2) Motor overload due to motor damage or pump impeller wear, or a system change (they...

The answer to your question should be covered in the paper: "Explicit formulas for the calculation of regenerated noise in ducts" by Tim M Marks The entire paper is available online. Do a google search and you should find the downloadable paper. The link is below but I find that long links...

Wire rope isolators have several advantages over conventional single axis rubber or spring isolators. 1)They are not affected by extreme heat or cold (within reason of course,) nor oils or other corrosives which destroy rubber or neoprene isolators. 2)They can be mounted in any attitude...

In a typical industrial setting, the steam flow in a pipe rarely generates problem noise levels. High noise levels are actually generated upstream at a valve or orifice. The turbulent flow/sound is then propagated down the pipe and out as noise. If you want to start somewhere then look up the...

Over many years, I have never actually hit a bearing defect frequency dead on (i.e. spectrum peak differs from defect frequency). Even if my FFT resolution is OK, there always seems to be a small 1 to 5 Hertz differnce. In fact if you calculate the bearing defect frequencies from the standard...

How about doing it the other way. Ultrasonic cleaners excite the liquid so it cleans parts thoroughly. Maybe you can apply an untrasonic exicter to the tank so that the liquid will flow into the voids better and bubbles might be dislodged at the same time.

I am not sure about your set-up, but with my proximity probes, a DC voltage is first applied to the probes (excitation voltage?) on one set of terminals and the gap voltage (varying DC signal = AC signal if the gap is changing)is generated on the second set of terminals (output). The base gap...