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Estimating blade stiffness through sound recording

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arg0 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote arg0 Quote  Post ReplyReply Direct Link To This Post Topic: Estimating blade stiffness through sound recording
    Posted: 12/02/2010 at 5:30pm
Hi all,
to avoid off-topics in the OSPblades Forum Testing thread, I'm opening a new thread.

Without going into complex mechanical considerations like it has been done in other threads, a simple way to estimate the hardness stiffness vibration frequency of the membrane mode (see this post for indication of what this represents) of a blade is to record the sound of a ball dropped on the center of the blade, while the handle is held lightly with one hand, and then looking at the highest peak of the spectrum of the recorded sound.

It goes like this (see also the attached images):
1. download and install Audacity from http://audacity.sourceforge.net/
2. Launch Audacity, press the record button.
3. Put the bat horizontally close to the microphone, holding it lightly with one hand.
4. Let a table tennis ball drop a few times on the bat from about 10-15 cm (4-6 in) height.
5. Stop recording.
6. Select Menu Analyze -> Plot Spectrum
7. Find the frequency of the highest peak in the spectrum and report it

This is Audacity showing the record button and an already recorded sound:


This is the Plot Spectrum option:


This is the spectrum: move the mouse (crosshair cursor) vertically close to the highest peak and read the corresponding frequency of the peak (highlighted in red):


It's really simple and requires no longer than 2 minutes.
(For the more technically minded, I know, this gives info only on one vibration mode, but it's nevertheless an easy way to estimate hardness stiffness...)

In a next post, I am going to attach a table with the frequency of quite some blades. It would be great if you could post your measurements, so I can add them to the table.
I'm especially interested in new blades that are not already in the table.

EDIT: changed stiffness to hardness, thanks davidz for pointing this out.
EDIT: replaced hardness with stiffness after pnachtwey's post
EDIT: replaced stiffness with vibration frequency of membrane mode and provided a link to further information


Edited by arg0 - 07/01/2017 at 10:33am
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Post Options Post Options   Thanks (0) Thanks(0)   Quote arg0 Quote  Post ReplyReply Direct Link To This Post Posted: 12/02/2010 at 5:42pm
This is the table:
uploads/20417/Blade_frequencies_Nov-2010.xls

I contribute to keep it updated in the tt-news.de forum, that's why the notes are in German (I only translated the headers).

Short word list:
lackiert, versiegelt: varnished
gerade: straight
dick: thick
gekürzt, geschliffen: shortened

Enjoy!
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Post Options Post Options   Thanks (0) Thanks(0)   Quote davidz Quote  Post ReplyReply Direct Link To This Post Posted: 12/02/2010 at 5:52pm
A list of the blade's sound frequency could be very useful.  Thanks!
 
I used the same software check the blade's spectrum with/without rubber.  It helps tuning a rubber and modifying the size of my blade.
 
Blade frequency is just one characteristic, which tends to measure the hardness of the blade. Another characteristic is amplitude of the blade's virbration, which is related to blade's stiffness. Unfortunately, this could not be measured using software.
 
 
 
One thing
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Post Options Post Options   Thanks (0) Thanks(0)   Quote pnachtwey Quote  Post ReplyReply Direct Link To This Post Posted: 12/02/2010 at 5:59pm
Good stuff,  how about the decay?   I have a 729 bomb that almost sounds like a musical instrument when hit.   The 929 Bomb sound is clear and not muffled.  I also have an LKT Instinct blade that is lower pitched but with an shorter/muffled sound.   A clearer longer sound indicated that the wood is not damped and doesn't lose energy quickly as a blade with a shorter muffled sound and more damping. A blade with more damping would not return as much energy to the ball.

I also have wondered if the higher frequencies help.   For instance if the ball has a dwell time of 2-4 milliseconds wouldn't it be best if the frequency of the paddle was lower than 1328 Hz and closer to having a period twice the dwell time of the ball on the paddle?   If the paddle pushes back mach faster than the rubber then the ball will separate from the rubber on the rebound before the rubber has had a chance to return most if its energy to the ball.

I do think that Arg0 has hit on something important.
I think there is a best frequency for the primary mode.
Everyone knows that pushing a child on a swing at the wrong rate is inefficient.





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Post Options Post Options   Thanks (0) Thanks(0)   Quote Vladovich Quote  Post ReplyReply Direct Link To This Post Posted: 12/02/2010 at 6:09pm
Does this measurement depends on the quality of our microphone? Can the microphone itself cut of some high frequencies?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Best99 Quote  Post ReplyReply Direct Link To This Post Posted: 12/02/2010 at 8:13pm
Of course it can. If you would like to record precisely all the frequencies, you would have to use a professional microphone (available on music studios, for example).
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Pioneer Quote  Post ReplyReply Direct Link To This Post Posted: 12/02/2010 at 8:25pm
Doesn't rubber's density count here as a major factor ?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote pnachtwey Quote  Post ReplyReply Direct Link To This Post Posted: 12/02/2010 at 8:32pm
A good microphone doesn't need to cost a lot.  I have one of these  
http://pro-audio.musiciansfriend.com/product/Blue-Snowball-USB-Microphone?sku=279015
Oops,  that is more than a sheet of T05.
I have one of these and the quality is pretty good for the price.  The frequency range far exceeds what is required for testing blades audio responses.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Best99 Quote  Post ReplyReply Direct Link To This Post Posted: 12/02/2010 at 8:41pm
Ok, but anyway, who is going to spend about 100 dollars just to buy a microphone to see how fast/stiff is a blade :P?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote arg0 Quote  Post ReplyReply Direct Link To This Post Posted: 12/03/2010 at 2:18am
I think the measurements should be quite consistent across user settings, because the spectrum does not depend (much) on intensity and microphone sensitivity (also a cheap laptop microphone should be sufficiently linear in that range).
There is some dependency on other factors, too, e.g. how firmly you hold the blade etc. Some time ago I have tried with my crappy laptop microphone and, some time later, with a better one and the difference I got was compatible with variations due to other factors (about 20-30 Hz if I remember well). So there's no need to buy expensive equipment (microphones and tenergys ;-) ).

These numbers should not be read as exact values, but as approximations to about 50 Hz.
I mean, a difference of 30 Hz is quite negligible and may depend on setup, a difference of 100 Hz is surely due to the blade characteristics.

@Pioneer, I'm testing only the blade, there's no rubbers on it.


Edited by arg0 - 12/03/2010 at 2:19am
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Post Options Post Options   Thanks (0) Thanks(0)   Quote vvu.tee Quote  Post ReplyReply Direct Link To This Post Posted: 12/03/2010 at 2:43am

thanks arg0, really useful info, I've got 2-3 Korbels FL, I will test it on next weekend - that will be fun... what is the relation between the stiffness and the peak sound/vibration. also, how would you differentiate between the effects on vibration by the stiffness (elasticity) and hardness (plasticity).

btw, non-destructive testing is not really my cup of tea, but what do you thing, can you extend the test to compare stiffness of different designs/wood types, i.e totally different blades, or just test for variation within the same model?

some engineering insight will be helpful...?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote arg0 Quote  Post ReplyReply Direct Link To This Post Posted: 12/03/2010 at 4:48pm
One day I will dig into the physics of table tennis, but for now I will just limit myself to empirical considerations: with a ball bounce test, the ball has not much energy, so the bat only undergoes tiny elastic deformations. What is not true is that in this case only the outer layer contributes: otherwise, say, all hinoki blade would have similar frequencies, which is definitively not the case.

PS: for in-depth discussions about the mechanics involved, see these threads:
http://mytabletennis.net/forum/forum_posts.asp?TID=26762
http://www.tabletennisforum.gr/forum_posts.asp?TID=11262
I prefer to keep it simple here. However, if you spot something there that can contribute to this discussion, please post it.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote atv Quote  Post ReplyReply Direct Link To This Post Posted: 12/05/2011 at 9:52pm
Digging this thread out from reading arg0's post in Calix review, interesting method, i want to use it on a table our club recently purchased, I found this table biting off significant speed and spin from the ball but have no objective evidence, my friend has a set of professional piano calibration devices i could borrow. 

So the harder a surface is the higher pitch it will provide? Will it also apply to something as big as a table? 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote arg0 Quote  Post ReplyReply Direct Link To This Post Posted: 12/06/2011 at 1:50am
In principle, yes, although I'm no material science specialist and one year later I still haven't had the time to read the technical posts I referred to.
What is clear is that with tiny ball bounces as I used to make for measurements, one tests the blade's response at slow speeds. However, not only the outer layers are involved, because I tested several wood with kiso hinoki outer layers and got frequencies from 1300 to 1800 Hz.
I wish I had a way to launch balls at a predetermined speed to see if the first resonance frequency changes at higher speeds. Maybe for a first test I could simply block the blade handle between books and manually throw balls at it. Speed won't be consistent but at least I'll be able to see if there's a frequency shift.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote pnachtwey Quote  Post ReplyReply Direct Link To This Post Posted: 12/06/2011 at 1:08pm
I am bothered about the assertion that blade hardness is determined by frequency.
I like to do my absurdity tests and if the assertion can't pass that then the assertion is wrong or there is more to it than what is stated.
So why do marimba keys sound different if they are made of the same kind of wood?   The answer is size not hardness. Now I do believe that if one were to try to bend a larger marimba key it would flex more than a shorter one.

So why was stiffness replaced by hardness?

Arg0, an object will vibrate at its natural frequency but that can be changed by damping. Rubbers are good dampers and will reduce the frequency of oscillation
http://en.wikipedia.org/wiki/Damping

Anther thing I find interesting is that the period of oscillation is much shorter than the dwell time. This would mean the blade would oscillate a cycle to two times while the ball is in contact with the rubber. That would be like push a child on a swing at a rate faster than the natural frequency.   I would test this out on a hard bat or even a bare wood slow paddle.




     
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Post Options Post Options   Thanks (0) Thanks(0)   Quote arg0 Quote  Post ReplyReply Direct Link To This Post Posted: 12/06/2011 at 5:14pm
You've got a point there, so I put stiffness back. Actually I believe is that what I am measuring is frequency of the fundamental bending mode of the blade, which is fixed at one end (the handle). So it is rather related to flexibility, rather than hardness.

I have not considered rubbers, as blades alone are already complex enough for me to understand.

Do you have any estimate on how much dwell time is in table tennis shots?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote pnachtwey Quote  Post ReplyReply Direct Link To This Post Posted: 12/06/2011 at 6:16pm
Originally posted by arg0 arg0 wrote:

Do you have any estimate on how much dwell time is in table tennis shots?


1 millisecond seems a like a reasonable number. If the ball spends half of its time decelerating and have accelerating again then the deceleration time would be about 0.5 seconds.   If we assume the paddle to be stopped and the ball is hitting the paddle at 10 m/s the average speed during decal will be 5 m/s.   Multiply this by 0.5 milliseconds and the result is 2.5mm deceleration distance.   This means the ball deforms, the rubber deforms and the blade deforms about 2.5 mm during the impact and this is not a fast impact. If the dwell time were longer the deformation would need to be proportionately greater.

It seems to me that a blade that vibrates too fast would vibrate out of phase.
I should do a simulation with two springs and make one spring much stiffer than the other just to see what would happen.

I know a TT ball will deform a lot.   I wish I had a good high speed camera.   Not the 500 Casio toys.   I mean a good 10,000 FPS camera. It is only $100K. If any body chips in I may buy one just to answer these questions.

BTW, what do you think the average force between the paddle and the ball during impact if the relative speed is 10 m/s? It isn't hard to calculate but you have to assume a dwell time that makes sense. Assume 1 millisecond.

I am amused at those that talk about extra dwell time on the paddle. The differences can probably be measured in microseconds.








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Post Options Post Options   Thanks (0) Thanks(0)   Quote arg0 Quote  Post ReplyReply Direct Link To This Post Posted: 06/30/2017 at 6:11pm
I've decided to contribute the data that I've collected. The majority of data comes from the table in the German forum I mentioned above. I have added the data for all the blades that I've measured over the last years. Enjoy!

If you have measured frequencies for any blade not on the list, or found frequencies that significantly differ from the ones listed, please report.


Brand Model Handle Weight (g) Frequency (Hz)
Donic Defplay Senso

829
Nittaku Miyabi FL 83 864 and 1218
American Hinoki Ancient Kauri ST 93 906 and 1233
W. Froese Def/All

976
Donic Defplay Senso konkav
83 977
Joola Rossi Fire

1006
Stiga Anniversary LE2092

1017
Stiga Allround Stellan Bengtson ST
1024
Joola Allround
83 1039
Joola Play-OFF

1041
Stiga Alser 69
96 1050
LKT Toxic3

1059
Nittaku Violin
86 1059
Weltklasse Prestige Carbon

1063
Stiga Energy Wood
86 1068
Butterfly Timo Boll All+

1078
Double Fish 167 FL
1083
Imperial Eberhard Schöler ST 97 1087
Butterfly Secretin ALL

1088
Butterfly Korbel Japan

1091
Butterfly Primo Japan
80 1091
Stiga Allround Classic

1092
Stiga Allround Ulf Tickan Carlsson

1096
Stiga Jubi LE1054
85 1096
Gewo Super Control

1099
Donic Epox Control
80 1100
Stiga Offensive Classic

1100
Butterfly Grubba all+ ST 80 1101
Butterfly Grubba ALL+
80 1101
Butterfly Boll Forte
90 1105
Donic Appelgren Falcon
75 1105
Stiga Offensive Classic CR

1107
Imperial Sensor
91 1108
Butterfly Maze Passion
93 1109
Stiga Def Wood C-Serie
77 1110
Nittaku Vioncello ST
1115
Stiga Jubi LE Serie
85 1123
Butterfly Tempest
80 1132
Yinhe W-6
92 1135
Banda Century 5
88 1138
Banda Scandik WRB
76 1140
Butterfly Primorac Japan ohne Seriennummer

1141
Stiga Anniversary D202

1145
BBC Fiddler CO 80 1146
Butterfly Primorac Classic

1146
Stiga Allround Hans Alser 1983

1148
Stiga alte dicke Hölzer

1150
Donic Allplay alt (weiße Linse)
86 1156
Joola Rosskopf Fire
78 1156
Stiga Tube Allround
88 1156
Avalox BT 550

1158
Butterfly Boll Spark ST 89 1160
Butterfly Boll Spark
89 1160
Stiga Offensive CR
81 1160
Nittaku Violin FL 80 1161
OSP Expert SQST 87.5 1161
Butterfly Boll Spark ST 83 1162
Butterfly Boll Spark
83 1162
Stiga Offensive CR
79 1163
Schöler-Micke Allround+

1164
Butterfly Primo Classic

1166
Donic Appelgren Allplay
85 1167
Joola Sting
100 1168
Butterfly Guo Yue Japan

1170
Nittaku Violin ST 87 1170
Stiga Alser All C-Serie
92 1170
Nittaku Violin L-Size ST 85 1178
Stiga Energy Wood

1178
Stiga Off Classic
75 1178
Avalox Blue Thunder 550A

1180
Nittaku Violin L-Size ST 86 1180
Nittaku Violin L-Size ST 88 1180
TSP Black Blizzard

1180
TSP Black Blizzard Carbon Off

1180
Yinhe EC-13
88 1180
NEXY Lissom ST 83 1181
Avalox P500

1183
OSP Expert SQST 88 1183
Schildkröt Futec

1183
Butterfly Chuan Chih-Yuan ST 86 1184
NEXY Higgs ST
1184
Stiga Graphite Wood
94 1185
Butterfly Primorac Japan AN
87 1188
Donic Persson Powerplay

1188
Butterfly Chuan Chih-Yuan
86 1189
Nimatsu Celsior 5.6 Direct ST 79 1189
Stiga Offensive CR

1189
Butterfly Schlager Inspire
96 1190
Nimatsu Celsior 5.6 Direct ST 77 1190
NEXY Lissom Special ST 85 1193
Stiga Off Classic
85 1194
Stiga Energy Wood WRB FL 81 1199
Stiga Energy Wood WRB
81 1199
Donic Waldner Senso Carbon

1200
OSP Ultimate RST 93 1200
Yinhe LQ-1
91 1200
Yinhe MC-3
88 1200
Butterfly Maze Passion

1201
Imperial Eberhard Schöler ST 102 1202
Butterfly Korbel deutsch

1204
Donic Waldner Senso Carbon
84 1204
Tibhar Black Silver
88 1204
Butterfly Kenny Style ST 91 1206
NEXY Lissom ST 84 1206
Juic Kalinic

1207
Butterfly Adolescen

1209
Donic Epox Powerallround

1209
Butterfly Boll Off-

1210
Nittaku Acoustic
89 1210
Donic Persson Power Play V2
84 1211
Ross Leidy Vagabond AN 88 1211
Nimatsu Celsior 5.6 Direct ST 77 1215
Yinhe 980
89 1217
DHS Hurricane King FL 87 1218
Donic Waldner Senso Carbon
85 1221
Stiga Optimum Sync

1224
Butterfly Bazelart ST 83 1225
Yinhe W-6 FL 85 1225
Yinhe W-6
85 1225
Ross Leidy Storms of Jupiter ST 85 1226
Butterfly Adolescen
89 1227
Tibhar IV-L Light Contact
81 1227
Nittaku ANV WL
77 1230
Stiga Clipper CR

1234
Yinhe 980

1234
Yinhe Stock ST 81 1234
Yinhe Stock Premium
80 1234
ARTTE Nuvola ST 85 1237
Stiga Offensive NCT
82 1239
Butterfly Boll Spark FL 82 1240
Butterfly Boll Spark
82 1240
Darker 7P-2A.DF ST 82 1240
Donic Persson Powerallround

1240
Nittaku Violin ST 88 1240
Nittaku Violin
88 1240
Stiga Tube Light
90 1241
NEXY Amazon ST 79 1242
Avalox Blue Thunder 555
84 1243
Avalox AVX Blue Thunder 550

1246
Nittaku Acoustic ST 79 1246
OSP Virtuoso SQST 86.1 1246
OSP Virtuoso SQST 89.3 1248
Joola Carbon Schweden
84 1250
Yasaka Extra

1251
Butterfly Jonyer-Hinoki
74 1260
Nittaku Latika ST 84 1260
Stiga Hypertech 35/45
80 1260
Tibhar Allround Classic Junior

1260
Tibhar Icon Sensitec
83 1261
Cornilleau Hinotec ALL+ FL 84 1263
Donic Waldner Offensiv 2016 Limited

1263
Tibhar Xeon Sensitec

1264
Butterfly Korbel OFF- Japan
88 1265
Stiga Saive Power WRB

1265
NEXY Lissom ST 84 1266
NEXY Spartacus FL 82 1269
Butterfly Schlager Precision
80 1270
Nittaku Runlox 5
88 1271
Donic Waldner Dicon

1273
OSP Virtuoso SQST 89.8 1274
Stiga Metall Wood
91 1275
NEXY Lissom FL 87 1278
Avalox P500
88 1280
Nittaku ANV
91 1280
Butterfly Yoshida Kaii

1281
Donic Waldner Diablo Senso

1282
Stiga Allround NCT
82 1282
Andro Leader
86 1288
Stiga Ebenholz NCT VII

1288
Yinhe Earth-1 CO 87 1288
Stiga Arctic Wood ST 82 1289
Nittaku Acoustic ST 85 1289
Stiga Offensive Wood NCT
85 1290
NEXY Tamar VII ST
1291
Nittaku Tenor FL 91 1291
Stiga Ebenholz NCT V

1291
Nittaku Latika ST 80 1296
Butterfly Korbel OFF Magic Hand
93 1297
OSP Virtuoso+ SQST 89 1298
Yinhe 2011
92 1300
Avalox P500
80 1303
Stiga Tube Light

1303
Weltklasse Futec II

1304
Yasaka Ma Lin Soft Carbon
90 1305
Stiga Clipper

1307
Butterfly BalsaCarbo X3

1309
Butterfly Schlager Precision
84 1309
NEXY Calix ST 84 1309
Yinhe K-3 FL 86 1310
Yinhe K-3
86 1310
Nittaku Septear
79 1311
Donic Persson Powerallround
80 1313
Stiga Clipper Wood
89 1313
Avalox BT 555

1315
Joola S. Fetzner Carbon

1317
NEXY Calix ST and FL
1320
NEXY Color FL 89 1320
Nexy Color
89 1320
Stiga Hybrid Wood
85 1321
Stiga Hybrid Wood
99 1322
Butterfly Defence ST

1323
NEXY Olam ST 83 1323
Nittaku ANV WL

1324
Butterfly Innerforce AL
91 1326
OSP Virtuoso
88 1328
Tulpe 702

1331
Darker Legato Point Carbon FL 81 1333
Nittaku Acoustic ST 85 1333
OSP Virtuoso SQST 87.6 1333
TT-Manufaktur Basalt ST
1333
NEXY Arirang ST 85 1337
OSP Virtuoso+ CO 88 1337
NEXY Calix FL 83 1340
Butterfly Innerforce AL FL 88.5 1341
Tulpe Black Power

1343
Stiga Clipper Wood

1344
TT Manufaktur Spinmaster Plus

1344
DHS PF4-32

1345
Avalox BT 777
90 1348
NEXY Peterpan ST and FL
1349
NEXY Rubicon ST and FL
1351
Butterfly Korbel SK7

1355
NEXY Peterpan ST 85 1358
Stiga Ebenholz NCT V
88 1358
NEXY Peterpan ST 85 1359
NEXY Peterpan ST 85 1370
American Hinoki Ancient Kauri FL
1374
Stiga Ebenholz V
90 1375
Andro Super Core System off

1381
Yinhe M-6
86 1390
NEXY Kanaph ST 84 1392
XIOM Michelangelo

1393
NEXY Chedech ST and FL
1395
Stiga Tube Aluminium
83 1396
Ross Leidy Rapscallion ST 84 1398
Stiga Tube Carbo
88 1399
Tibhar Nimbus OFF

1400
Yinhe 896
84 1400
Yinhe W-5
85 1400
Butterfly Keyshot Light
82 1408
Stiga Tube Carbo

1420
Nittaku Septear

1423
Donic Persson PowerCarbon Senso
90 1431
Gewo Power System 4.0

1441
Butterfly Innerforce ULC

1442
Butterfly Timo Boll ALC

1450
Butterfly Viscaria

1452
Butterfly Boll Spirit
87 1453
Butterfly Mazunov

1455
Soulspin Koto Medium Speed 3DST 86 1455
Yinhe K-1
87 1455
Butterfly Boll Spirit
96 1458
Butterfly Keyshot Light
84 1461
Weltklasse Speedster

1465
ARTTE Mantra

1473
Butterfly Jun Mizutani
90 1475
XIOM Stradivarius

1481
Butterfly Kiso Hinoki V ST 79 1482
NEXY Zealot ST 83 1491
Nittaku S-5 ST
1500
NEXY Calix II FL 86 1505
Nimatsu Maestro ALL+ ST 80 1517
Butterfly Kiso Hinoki V
79 1527
Butterfly Keyshot Light
85 1531
Donic Opticon

1531
Butterfly Kong Linghui Spezial
84 1538
Yinhe M-3

1543
Yinhe W-3
88 1545
Butterfly Keyshot Light
83 1555
Andro Kinetik CF OFF-
86 1556
NEXY Calix II ST and FL
1556
Butterfly Michael Maze ST 91 1566
Butterfly Michael Maze
91 1566
Tibhar Inca ST 85 1571
Donic Carbo System

1574
Butterfly Timo Boll ZLC

1576
Yinhe T-7 FL 87 1578
Yinhe T-4
78 1580
Butterfly Viscaria Light

1584
Yinhe T-7
87 1587
Butterfly Kiso Hinoki V
83 1588
Yinhe T-8

1593
NEXY Oscar ST 85 1601
Yinhe T-7 Light ST 65 1604
NEXY Qabod ST 88 1609
Tibhar Black Carbon
80 1610
Yinhe T-2

1623
BBC 9-10-9 CO 83 1631
XIOM Jazz FL 83 1635
Yinhe T-5

1639
Tibhar Samsonov Carbon
97 1651
Nimatsu Maestro OFF FL 80 1654
Tibhar Samsonov Carbon

1657
Butterfly BalsaCarbo X5
75 1659
Butterfly Photino

1661
Best of Five Carbon AR Light

1674
Butterfly Gergely
94 1677
Yinhe T-3
86 1695
Butterfly Schlager Light
86 1700
Butterfly Primorac Carbon OFF+

1705
Butterfly Gergely Carbon

1710
Imperial Balsa Carbon

1716
Yinhe T-6

1777
TSP Hinoki Pure
88 1790
Joola Rossi Force

1794
Butterfly Schlager Carbon

1950
Yinhe T-11
70 2000
Nittaku Excellent AAA

2006
Yinhe T-1

2044
Nexy Arche & Nittaku Violin LG.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote arg0 Quote  Post ReplyReply Direct Link To This Post Posted: 07/01/2017 at 10:29am
Just wanted to cross-link this with another thread, dealing with the same subject.
Nexy Arche & Nittaku Violin LG.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote adyy Quote  Post ReplyReply Direct Link To This Post Posted: 11/22/2018 at 4:51am
I have read this thread and the other thread and I measured a blade that I have just built. And I have some questions, if someone can help me.

I have made the Spectral Analiser analyse and Audacity recording at the same time.
Here is the data obtained with Vuche Spectral Analiser:



and here is what I recorded with Audacity:



So, the data obtained is close (in the 50 hz range quoted above), respectively [email protected] and [email protected]

But why the decibel value is so different, since it is the same blade and the measurements/recording with these 2 tools what made simultaneous? The phone was placed near the blade and the "laptop" microfone was some Logitech headset microphone placed around 15 cm away from the blade.

Here is also the MP3, attached:

Is it normal or I may have made some mistake?
Thanks!!!




Edited by adyy - 11/22/2018 at 4:53am
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Post Options Post Options   Thanks (0) Thanks(0)   Quote zeio Quote  Post ReplyReply Direct Link To This Post Posted: 11/22/2018 at 5:40am
The units are different. dB ≠ dBFS(decibels relative to full scale).

https://www.audiomasterclass.com/newsletter/what-is-the-difference-between-0-db-and-0-dbfs
Quote Decibels are used to describe differences or changes in level. 0 dB means 'no change'.

Values in dBFS are used to describe signal levels in comparison with the highest level a WAV file can handle.


Edited by zeio - 11/22/2018 at 5:45am
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 adyy Quote  Post ReplyReply Direct Link To This Post Posted: 11/22/2018 at 7:34am
Thanks Zeio! The Lightbulb is brighter now!

And I suppose the difference between the 1442Hz (Huawei P10) and the 1489Hz (Logitech mic + laptop sound chip) is caused by the different hardware used. And it is in the 50 Hz normal "variation" range.
So, no measurement mistakes.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote adyy Quote  Post ReplyReply Direct Link To This Post Posted: 11/22/2018 at 8:03am
Now there is a new question, for the more experienced than me.
I just measured another 3 blades:

1) Yinhe T8s - 1593Hz @ 84db
2) Nittaku Flyatt Carbon - 1378Hz @ 76db

3) *another blade made by me - 1335Hz @ 82db

Between 1) and 2) there is a clear difference. Yinhe is faster than the Nittaku in real life too.
But the 2) and 3) have the frequency in the 50hz range, so they should be very close one to the other in speed. 
But what might the dB difference mean? 
My first tought is that because they have different COR, the 3rd returns more energy, louder! But it returns the energy to the ball or it dissipates to the environment as sound energy? I would tend to think the second.

Or that db values should be totally ignored because they mean nothing?

* this is a mahogany-fiberglass-ayous-fiberglass-mahogany blade of 5.5mm tickness, 91.8 grams.
* it is built for a colleague at work and was not tested yet (he is waiting for the rubbers), so I have no idea how it plays. But I estimate it to be somewhere around an ALL+ rating.
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