The final root cause and delivery of the solution was developed once we changed the fan in the system. This is typically fairly easy, however, the second supplier’s fan experienced a very similar failure in sound quality.

One of the largest obstacles causing large schedule delays (equals money) was neither supplier knew how to make the necessary engineering changes to improve the sound quality. They both had purchased virtually the same technology we used for this project but do not possess the expertise to test, analyze and re-engineer their own product for sound quality. This was proven when they were unable to measure the same sound (duplicate the problem) or develop any root cause analysis, engineering corrections or containment.

We developed a 3-way course of action with each supplier and the brand in order to contain the problem, make necessary engineering corrections to the fan and re-qualify them for production and shipping.

Below is the 1/3 octave band A-weighted (dBA) data acquired after the changes.

 

 

 

 

 

 

 

 

 

 

 

 

 

The interesting and one very important item to take note of here is, the overall dBA sound pressure is slightly higher after the change. Basically, the change is within the measurement tolerances. The largest reduction is in the 4000Hz band. However, many would not view this as a success due to the dBA becoming higher, except that...

 

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Root Cause