How work Tone Measurements instrument?

[Morgil]

Hi.

Could you say me how works Tone Measurement tool in LabView 8.5.1?  I need this information for my diploma thesis. It use FFT or Fourier transformation?

Thank you! 

[JÞB · Accepted solution]

Although the Express vi help is vague (Its meant for beginners so it discusses functions at high level) If you convert the express vi to  a sub-vi you can open its heirarchy (see picture above)

Exploring the heirarchy with Help on yields answers and more detailed explainations of the underlying functions.  A FFT is used to compute the tone information.