Check belt tension sonic meter method?

[CruiseRT]

Sonic meter is a device that measures sound, so I thought I would have a go at it to see what I could come up with. BRP uses the Gates 507C Sonic meter, so I read the manual and they explain everything you need. Take a look, I might not have explained what I did very well but it seems quite simple given BRP gives you all the numbers except the measured frequency. These numbers are from a 2013 RT Service manual.

Theory.jpg

According to Service manual for 2013 RT:

Belt tension is 1050N +-150N and
Mass 8.4 g/m
Width 28.0 mm/R
Span 1028 mm

I recorded the frequency of my belt with an old Sansa MP3 player. I just recorded the belt as I strummed it like a guitar string.
I opened the sound recording in a program called Kwave, A Linux program for analyzing sound waves:I use a Linux operating system, but you should be able to find a Windows program to do the same thing.
wave.jpg
Then I measured the wave cycle time where the sonic meter takes its measurement (Actually measured about 12 cycles and averaged them) The wave below is expanded out so you can see the pattern.
time.jpg
Then I converted the time to a frequency.
Frequency in Hz.=1/time in seconds
Now just plug all the numbers into the formula provided by Gates.
T=4 x M x W x S² x f² x 1e10^-9

M = Mass = 8.4 g/m
W = Width = 28.0 mm/R
S = Span = 1028 mm
f = Frequency = 27.4
(x 10-9 Just move decimal 9 places to the left)
746.42= 4 x 8.4 x 28.0 x 1056784 x 750.76 x 1e10^-9

Since everything is constant except the frequency you could simplify

T=0.9942223872 x f²

T=746.42 Newtons

746.42 Newtons = 167.8 lbs.

My Krikit checks it at 175 to 180.

What do you think, could this be useful?