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Expressing relative blade speed

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Post Options Post Options   Thanks (0) Thanks(0)   Quote JacekGM Quote  Post ReplyReply Direct Link To This Post Posted: 07/01/2017 at 8:40pm
Originally posted by zeio zeio wrote:

Originally posted by qpskfec qpskfec wrote:

I would like to see results from testing both sides of a combo blade.

A combo blade being one with an asymmetric design - different composition on each side, typically made for people to use inverted rubber on one side and LP on the other.

If one side is much softer wood than the other, are the frequencies the same?

Frequencies should be the same, but the amplitude could be different on either side.

This I am not convinced about... actually, I am pretty sure the pitch will be different when using one side vs the other.
(1) Juic SBA (Fl, 85 g) with Bluefire JP3 (red max) on FH and 0.6 mm DR N Desperado on BH; (2) Yinhe T7 (Fl, 87 g) with Bluefire M3 (red 2.0) on FH and 0.6 mm 755 on BH.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote JacekGM Quote  Post ReplyReply Direct Link To This Post Posted: 07/01/2017 at 8:44pm
Originally posted by arg0 arg0 wrote:

For a related discussion, see this thread.
Wow, this is pretty much very related... Thanks for pointing this out.
(1) Juic SBA (Fl, 85 g) with Bluefire JP3 (red max) on FH and 0.6 mm DR N Desperado on BH; (2) Yinhe T7 (Fl, 87 g) with Bluefire M3 (red 2.0) on FH and 0.6 mm 755 on BH.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Baal Quote  Post ReplyReply Direct Link To This Post Posted: 07/01/2017 at 8:52pm
In terms of evaluating blades, what have we had in terms of objective measures? Weight, and blade dimensions and thickness, and really that is about it. We also have completely subjective measures of "speed" and "control" with numbers that people pull out of thin air. So we don't really know how well something like this can work unless we try it. The blade manufacturers will never provide it, they thrive on EJs and confusion. In fact, I suspect a more detailed analysis of what these phone apps give would tell us a great deal, but just getting the one number is helpful within limits -- such comparing two blades that might be regarded as similar -- like a Donic True Carbon with one of the Btfl ALC blades for one example.

I know that there is obviously a certain quality of blades that makes them great that cannot be easily captured in a single number, but it might be surprising how few numbers we might need to home in something we would like a lot.

This reminds me of mountain bikes, which were not invented by any one person, but by grass roots innovation like this. I think this is one of the best things I have seen on TT forums in a long time, and it is quite interesting that the idea is "in the air" and it turns out that several people around the world have been playing around with this (so there is already a quite large database).

You guys who have been making these measurements are awesome.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Baal Quote  Post ReplyReply Direct Link To This Post Posted: 07/01/2017 at 8:54pm
Originally posted by JacekGM JacekGM wrote:

Originally posted by zeio zeio wrote:

Originally posted by qpskfec qpskfec wrote:

I would like to see results from testing both sides of a combo blade.

A combo blade being one with an asymmetric design - different composition on each side, typically made for people to use inverted rubber on one side and LP on the other.

If one side is much softer wood than the other, are the frequencies the same?

Frequencies should be the same, but the amplitude could be different on either side.

This I am not convinced about... actually, I am pretty sure the pitch will be different when using one side vs the other.



No, I am quite sure the blade will vibrate as something intermediate between what you would get if the blade had been made with all of one or the other materials.  I am inferring that from the two articles Arg0 cited earlier on acoustic analyses of blades. 

(By the way, I knew that the drum head is different from a TT blade because it is fixed around its entire perimeter, but it was still cool to look at).

By the way, Hozuki raised an interesting point.  Has anyone else given any thought to that?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote book4all Quote  Post ReplyReply Direct Link To This Post Posted: 07/01/2017 at 11:44pm
I think the recording hardware may make differences. That means different cell phones may produce different benchmark frequency numbers. 

The result will make a lot of sense from one person's collection because using the same recording device and still make quite a bit sense even using different recording devices. 

So adding cell phone model information may help to explain the differences. 

BTW this database of frequencies can help identify fake blades. :)


Edited by book4all - 07/01/2017 at 11:54pm
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Post Options Post Options   Thanks (1) Thanks(1)   Quote h0n1g Quote  Post ReplyReply Direct Link To This Post Posted: 07/02/2017 at 1:41am
Originally posted by book4all book4all wrote:

I think the recording hardware may make differences. That means different cell phones may produce different benchmark frequency numbers. 

The result will make a lot of sense from one person's collection because using the same recording device and still make quite a bit sense even using different recording devices. 

So adding cell phone model information may help to explain the differences. 

BTW this database of frequencies can help identify fake blades. :)


I have tried this. Again not 100% but I did the same test with a Pixel XL (Android), Samsung S7 (Android), iPhone 6S and iPhone 7 and the readings were within 4 hz so nothing that would completely move a blade into a different category.
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Post Options Post Options   Thanks (1) Thanks(1)   Quote zeio Quote  Post ReplyReply Direct Link To This Post Posted: 07/02/2017 at 4:03am
Here is modal analysis 101. An object has an infinite number of natural frequencies. With each natural frequency there is a corresponding mode shape, collectively known as the mode of vibration. The physical properties such as the mass, shape, and stiffness of an object dictate the frequencies it will vibrate at.

In modal analysis, an impact test would be performed on an object to observe its modes of vibration. The object would respond(resonate) to frequencies that correspond to its natural frequencies. The duration of impact(contact time) characterizes the frequency content of the input force. Thus, an ideal input is one that has the shortest duration, and with enough force, which would generate a constant response across the entire range. In real world tests, an impact hammer is carefully chosen to excite only the frequencies of interest in order to reduce noise.

For table tennis, the ball is the best impact hammer as it simulates real-world situations. A 1ms impact(the typical dwelltime for blade+rubbers) would excite modes below 1kHz, .5ms for those below 2kHz and so on. The wave generated by the impact would travel across and reflect within the boundaries of the blade. The lower end of the frequencies is responsible for both blade head and handle vibration and thus a lot of it would get absorbed by the hand. The upper end has more to do with just the blade head vibration and would travel away as sound.

As to why a combo blade would give a similar response on both sides. The frequency response of an object is constrained by its entire construction. As the mechanical wave will traverse the blade, one can't expect one side to not get affected by the other. This is the reason why a symmetrical blade with the same rubber on one side would feel different when the other side is paired with a different rubber.

Edited by zeio - 07/02/2017 at 4:10am
Viscaria FL - 91g
+ Neo H3 2.15 Blk - 44.5g(55.3g uncut bare)
+ Hexer HD 2.1 Red - 49.3g(68.5g 〃 〃)
= 184.8g
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Post Options Post Options   Thanks (0) Thanks(0)   Quote vvk1 Quote  Post ReplyReply Direct Link To This Post Posted: 07/02/2017 at 6:10am
Originally posted by h0n1g h0n1g wrote:

Added to the list. Just by looking at the numbers submitted from a number of different people, there is no doubt that this will be a decent indicator for blade speed.


Something feels a bit off with the latest table. Ebenholtz NCT VII is not slower than Ebenholtz NCT V or Ma Lin Soft Carbon.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote JacekGM Quote  Post ReplyReply Direct Link To This Post Posted: 07/02/2017 at 1:07pm
Originally posted by zeio zeio wrote:


...
....
As to why a combo blade would give a similar response on both sides. The frequency response of an object is constrained by its entire construction. As the mechanical wave will traverse the blade, one can't expect one side to not get affected by the other. This is the reason why a symmetrical blade with the same rubber on one side would feel different when the other side is paired with a different rubber.
Ok, this does strike a cord...
(1) Juic SBA (Fl, 85 g) with Bluefire JP3 (red max) on FH and 0.6 mm DR N Desperado on BH; (2) Yinhe T7 (Fl, 87 g) with Bluefire M3 (red 2.0) on FH and 0.6 mm 755 on BH.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote DonnOlsen Quote  Post ReplyReply Direct Link To This Post Posted: 07/02/2017 at 4:26pm
I was wondering if it would be instructive to add to the Table Tennis Blade Frequency (Speed) Compendium  a column of the manufacturers' rating of each of the blades.  Something of interest may be revealed.

Thanks..........
Donn
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Post Options Post Options   Thanks (0) Thanks(0)   Quote h0n1g Quote  Post ReplyReply Direct Link To This Post Posted: 07/03/2017 at 4:39pm
never mind, i copied the wrong cell.

Edited by h0n1g - 07/03/2017 at 5:21pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote NextLevel Quote  Post ReplyReply Direct Link To This Post Posted: 07/03/2017 at 5:42pm
Originally posted by Baal Baal wrote:

Originally posted by JacekGM JacekGM wrote:

Originally posted by zeio zeio wrote:

Originally posted by qpskfec qpskfec wrote:

I would like to see results from testing both sides of a combo blade.

A combo blade being one with an asymmetric design - different composition on each side, typically made for people to use inverted rubber on one side and LP on the other.

If one side is much softer wood than the other, are the frequencies the same?

Frequencies should be the same, but the amplitude could be different on either side.


This I am not convinced about... actually, I am pretty sure the pitch will be different when using one side vs the other.



No, I am quite sure the blade will vibrate as something intermediate between what you would get if the blade had been made with all of one or the other materials.  I am inferring that from the two articles Arg0 cited earlier on acoustic analyses of blades. 

(By the way, I knew that the drum head is different from a TT blade because it is fixed around its entire perimeter, but it was still cool to look at).

By the way, Hozuki raised an interesting point.  Has anyone else given any thought to that?





With the specific app slevin recommended, this is not a problem. At least, not AFAIK.
I like putting heavy topspin on the ball...
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Post Options Post Options   Thanks (0) Thanks(0)   Quote book4all Quote  Post ReplyReply Direct Link To This Post Posted: 07/03/2017 at 8:04pm
DHS PG7 83.6 1227
DHS T11+ 63.2 1851
Butterfly Viscaria 87.7 1485
HRT HUARUITE 85.5 1464
Donic Appelgren Allplay 78 1119
Donic Defplay Senso V3 88.6 1098
Donic Persson PowerSpeed 100.9 1399
Donic Persson PowerSpeed V1 1421
Yakasa Sweden Extra 85 1227
Yakasa Sweden Extra 82.5 1227
Yakasa Sweden Classic 1119
Tibhar Stratus Power Defense 86.2 1119
Nittgaku Monophonic 1141


Edited by book4all - 07/03/2017 at 8:42pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote h0n1g Quote  Post ReplyReply Direct Link To This Post Posted: 07/03/2017 at 8:46pm
Got an ITC Premier XR ST today, 90g heavy, clocking in at 1442.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote h0n1g Quote  Post ReplyReply Direct Link To This Post Posted: 07/03/2017 at 9:26pm
The comparison table can now be reached at www.ttbla.de
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Post Options Post Options   Thanks (0) Thanks(0)   Quote arg0 Quote  Post ReplyReply Direct Link To This Post Posted: 07/04/2017 at 12:47am
h0n1g, thanks for your efforts.
Please fix your "Popular Blade Averages" section: you're averaging some totally unrelated data. Better calculate the averages (or medians) once and report the value. Or, use a find function to find data in the table, but in this case you have to take care of spelling/model variations (like "Violin L-Size") or ("M. Maze", "M.Maze", "Michael Maze", "Boll Spirit", "Timo Boll Spirit", etc.).
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Post Options Post Options   Thanks (0) Thanks(0)   Quote AndySmith Quote  Post ReplyReply Direct Link To This Post Posted: 07/04/2017 at 7:23am
Originally posted by h0n1g h0n1g wrote:

Got an ITC Premier XR ST today, 90g heavy, clocking in at 1442.

ITC Premier XF, FL, 91g, 1399
ITC Premier XF, ST, 90g, 1356

Gewo Zoom Balance ALL+, ST, 92g, 1464
Gewo Zoom Balance ALL+, ST, 91g, 1421

Hmmmm.


Edited by AndySmith - 07/04/2017 at 7:34am
This was a great signature until I realised it was overrated.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote NextLevel Quote  Post ReplyReply Direct Link To This Post Posted: 07/04/2017 at 10:37am
Originally posted by AndySmith AndySmith wrote:

Originally posted by h0n1g h0n1g wrote:

Got an ITC Premier XR ST today, 90g heavy, clocking in at 1442.


ITC Premier XF, FL, 91g, 1399
ITC Premier XF, ST, 90g, 1356

Gewo Zoom Balance ALL+, ST, 92g, 1464
Gewo Zoom Balance ALL+, ST, 91g, 1421

Hmmmm.






Are you holding the blade too tight? Those are offensive blade scores.
I like putting heavy topspin on the ball...
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Post Options Post Options   Thanks (0) Thanks(0)   Quote h0n1g Quote  Post ReplyReply Direct Link To This Post Posted: 07/04/2017 at 11:40am
Originally posted by AndySmith AndySmith wrote:

Originally posted by h0n1g h0n1g wrote:

Got an ITC Premier XR ST today, 90g heavy, clocking in at 1442.


ITC Premier XF, FL, 91g, 1399
ITC Premier XF, ST, 90g, 1356

Gewo Zoom Balance ALL+, ST, 92g, 1464
Gewo Zoom Balance ALL+, ST, 91g, 1421

Hmmmm.



Those numbers are indeed very weird. Are you able to run them again?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Hozuki Quote  Post ReplyReply Direct Link To This Post Posted: 07/04/2017 at 12:19pm
Not so weird. I have already shown an inherent flaw in this method, which provides one possible explanation for this occurence, but nobody seemed to care.
To see whether it applies to this specific case, the full frequency chart is neccessary, though.

I'll make one more attempt at explaning it in more detail.

Blades can vibrate in multiple frequencies that can be very close together in terms of pitch and volume. This is especially evident in ALL+ Blades. Here is an example: (Hinotec ALL+)



Now I ask you: Which frequency would you pick to insert into the table? 1005? 1500? Or 12000?
As you can easily see, there is good potential for confusion. In fact, the first two peak freqs only have a 0.3 db difference in volume. Thus, a slight variation in blade weight, phone mic freq response or some other factor might lead to big differences between measurements of different people.

So what can we do to make things more accurate? Easy. Just don't rely on a single indicator that condenses the frequency chart into one freq peak number. Either find a better one, or use multiple indicators. Based on this, we can now all start thinking what would be suitable.

But I might be wrong since NextLevel said this issue does not matter since we all use the same app for recording. At least as far as he knows. So either he has better and more relevant information than I do, or...

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Post Options Post Options   Thanks (0) Thanks(0)   Quote h0n1g Quote  Post ReplyReply Direct Link To This Post Posted: 07/04/2017 at 12:21pm
The right frequency to pick is 1005 since it's the highest point vs amplification. Not sure what's confusing about that.

That is why slevin suggested a program with peak hold, so you don't have the inconveniences of need to scroll through and endless graph.

Edited by h0n1g - 07/04/2017 at 12:23pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote AndySmith Quote  Post ReplyReply Direct Link To This Post Posted: 07/04/2017 at 12:30pm
Originally posted by NextLevel NextLevel wrote:

Originally posted by AndySmith AndySmith wrote:

Originally posted by h0n1g h0n1g wrote:

Got an ITC Premier XR ST today, 90g heavy, clocking in at 1442.


ITC Premier XF, FL, 91g, 1399
ITC Premier XF, ST, 90g, 1356

Gewo Zoom Balance ALL+, ST, 92g, 1464
Gewo Zoom Balance ALL+, ST, 91g, 1421

Hmmmm.






Are you holding the blade too tight? Those are offensive blade scores.

I tried to hold the blade as softly as I could, and only by the handle (not the blade face at any point).

Although I did say in my initial review of the Zoom Balance that it was faster than I had expected an allround blade to be.  But still, the numbers are high.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote NextLevel Quote  Post ReplyReply Direct Link To This Post Posted: 07/04/2017 at 1:02pm
How thick is the blade?

I do have my usual fingers on the blade face but I suspect that doesn't matter as long as you don't grip it as if it is in a vice. I could not play with a blade that fast comfortably hence my surprisr.

Edited by NextLevel - 07/04/2017 at 1:03pm
I like putting heavy topspin on the ball...
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BH: MX-S 1.9 R
Lumberjack TT
No train, no gain.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote AndySmith Quote  Post ReplyReply Direct Link To This Post Posted: 07/04/2017 at 1:17pm
Originally posted by NextLevel NextLevel wrote:

How thick is the blade?

I do have my usual fingers on the blade face but I suspect that doesn't matter as long as you don't grip it as if it is in a vice. I could not play with a blade that fast comfortably hence my surprisr.

Thickness is 6.2mm.

It blatantly isn't that fast in the real world so something must be off somewhere.  I'll try different balls and different mobile phones.  I did the test with xiom seamless and my Oneplus One.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote h0n1g Quote  Post ReplyReply Direct Link To This Post Posted: 07/04/2017 at 2:54pm
Originally posted by AndySmith AndySmith wrote:

Originally posted by NextLevel NextLevel wrote:

Originally posted by AndySmith AndySmith wrote:

Originally posted by h0n1g h0n1g wrote:

Got an ITC Premier XR ST today, 90g heavy, clocking in at 1442.


ITC Premier XF, FL, 91g, 1399
ITC Premier XF, ST, 90g, 1356

Gewo Zoom Balance ALL+, ST, 92g, 1464
Gewo Zoom Balance ALL+, ST, 91g, 1421

Hmmmm.






Are you holding the blade too tight? Those are offensive blade scores.

I tried to hold the blade as softly as I could, and only by the handle (not the blade face at any point).

Although I did say in my initial review of the Zoom Balance that it was faster than I had expected an allround blade to be.  But still, the numbers are high.

Whats especially surprising to me are the XF numbers being SO close to the XR (1400 vs 1450)
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Post Options Post Options   Thanks (0) Thanks(0)   Quote h0n1g Quote  Post ReplyReply Direct Link To This Post Posted: 07/04/2017 at 3:37pm
So i wanted to check some things today and booted up Audacity and connected my Yeti Blue Snowball Mic (http://www.bluemic.com/products/snowball/), which is regarded as a pretty precise mic for its price-range.

I've measured a few blades that I recorded before using a Pixel XL (Android) phone. Here are the results:

KJH - Android - 1378
KJH - Yeti - 1364
Variance: 1.0%

TB ALC - Android - 1442
TB ALC - Yeti - 1429
Variance: 0.9%

Xiom Vega Tour - Android - 1291
Xiom Vega Tour - Yeti - 1296
Variance: 0.4%

Xiom Vega Pro - Android - 1399
Xiom Vega Pro - Yeti - 1385
Variance: 0.1%

Nexy Zealot - Android - 1399
Nexy Zealot - Yeti - 1396
Variance: 0.2%

ITC Premier XR - Android - 1442
ITC Premier XR - Yeti - 1437
Variance: 0.3%

So I think its save to say that mobile phones offer a pretty precise result given this check. Does this 'scientifically proof' anything? No but it at least shows that the recording equipment does not majorly influence the results.

I have also used different balls in this test (Nittaku P40+ and DHS D40+) and the results were practically the same.


Edited by h0n1g - 07/04/2017 at 3:39pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote book4all Quote  Post ReplyReply Direct Link To This Post Posted: 07/04/2017 at 3:44pm
Looks good to me.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote arg0 Quote  Post ReplyReply Direct Link To This Post Posted: 07/04/2017 at 4:06pm
Originally posted by arg0 arg0 wrote:

Originally posted by Baal Baal wrote:

There is a really cool animation here, int this case of a circular membrane under tension, but still really interesting.
http://www.acs.psu.edu/drussell/Demos/MembraneCircle/Circle.html

The animation is cool, but this is not how a table tennis blade vibrates. In the circular membrane animation the whole outer perimeter is fixed. In a blade, the only relatively fixed part of the blade face is where it meets the handle.

Slightly off-topic, but this link shows the shape of vibration modes for a tennis racket:
http://www.acs.psu.edu/drussell/Demos/tennis/tennis-1.html
This still does not fully correspond to the shape of the vibration modes of a table tennis blade, because vibrations of the string bed and frame are analysed separately, but they are closer than those for the circular membrane.

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Post Options Post Options   Thanks (1) Thanks(1)   Quote arg0 Quote  Post ReplyReply Direct Link To This Post Posted: 07/04/2017 at 4:41pm
By means of this acoustic frequency analysis the eigenfrequencies (or frequencies of vibration modes) of the blade can be determined. However, these cannot be directly matched to blade speed. To know how fast a ball will travel after impact, one needs to determine how much of the incoming energy is transferred back to the ball, and how much is absorbed by the blade, instead. This is a separate parameter (damping) and needs to be determined experimentally.
I've just started thinking about this. One could try to measure damping by how high (in %) the ball rebounds after impact (though I don't see an easy way to reliably measure this), or indirectly by analysing the decay of the sound after ball impact. Damping also reflects on the width of the frequency peaks, but given how messy the spectra are, it will not be possible to reliably measure the width of the peaks in the audio spectra. Analysing the decay time of the vibrations of a single ball impact is also not trivial, as I'll try to show in a next post.
Any thoughts?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Hozuki Quote  Post ReplyReply Direct Link To This Post Posted: 07/04/2017 at 5:18pm
Originally posted by h0n1g h0n1g wrote:

The right frequency to pick is 1005 since it's the highest point vs amplification. Not sure what's confusing about that.

That is why slevin suggested a program with peak hold, so you don't have the inconveniences of need to scroll through and endless graph.


Seriously, did you even try to read what I wrote? First of all, my chart IS the peak hold result of several bounces. Also, it's not an endless graph, in fact, I zoomed it in so it becomes more clear. Secondly, at some bounces, the lower freq had the higher amplitude, in some cases the higher freq had the higher amplitude. The difference in maximum amplitude is just 0.3 db. Do you have any idea how little that is? Nope, yet you still would confidently choose 1005 hz. No wonder the table is flawed with ppl like you around.

Thirdly, only because YOU don't have much variance between measurements of your standalone mic and your phone, doesn't mean others won't. There is something called frequency response of microphones, which is never perfectly linear (the difference can be quite a few db, which would be pivotal in my mentioned case). But since you consider a 'snowball' microphone an adequate tool for objective measuring, you obviously have no idea what you are doing.

But don't mind me, continue with whatever makes you happy.
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