Jul
03
2014

Reverse Engineering, It’s Music To Our Ears!

A recent project has attempted to find out why twenty violins from 1730 sound better than others. But why? Well…with the way in which many violins are constructed being the same, it is a puzzle for many manufacturers as to why some of these instruments produce a higher quality sound to their counterparts.

Many factors play a part; most obvious being the shape of the violin. Other issues feature such as the humidity during the assembly, the wood used to manufacture the violin and the actual wood density etc.

However, getting the data for the shape of the violins isn’t an easy task as touching these violins worth over £1.2million with mechanical equipment could potentially lower their value by damaging the finish.

An Instrument for success.

And how to complete this momentous task? Take a laser scan with a Portable Coordinate Measuring Machine with an attached Laser Line Probe (LLP) of course! In this way, a point cloud of the exterior shape good to about .003” can be obtained without having to touch the instruments. In this particular project each violin took 45 minutes to scan, with most of the time being taken up inspecting the cloud of points for holes in the data and then scanning again to fill them in.

Scanning the bulk of the outside took around 10-15 minutes and a small portion of time was afforded to deleting additional data gained from the jig which the instruments sat on. The Laser Line Probe is a line of sight instrument, and so anything scanned with its laser is picked up the cameras, added to the cloud of points and then saved once the data is satisfactory.

Inside-out.

Equally important for this project was the inside of the violins. Due to the violins being worth so much, cutting them open was not an option. Luckily, an MRI was used to provide point cloud data much like the Laser Line Probe can for the outside: Although the accuracy of an MRI machine is not as high as the LLP, it was more than adequate for this application. 10 minutes was then required by the MRI to map the inside of the violin and this data was then exported to a file for future use.

After data for both inside and outside the instruments were taken, the two pieces of data had to be brought together. The MRI also collected data on the outside of the violins and so the two readings were brought together in order to align the scans. Once aligned, the data was saved as one data set. From this aligned data set, the point cloud was analyzed and manipulated to be a 3D CAD model applicable in basically any CAD system.

This then allowed for the information to be sent off so new violins could be cut in the same way as their older counterparts, in the hope that these new violins will create a high-quality sound also. The results remain to be seen…or heard.


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