# How long the string tension last? Here is the answer (maybe)

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This was posted earlier in another forum. Repost it here in English and hope someone will find it interesting.

(1) Here is the theory. When you play a string, it will make sound. Sound is a wave, so there is frequency associated with it. The higher the tension, the higher the frequency. By analyzing the frequency changes, we could get some feeling how the string tension goes.

The first picture shows how a piano does, each notes with its frequency.

The 2nd picture shows a few rackets with different tension, and it's associated frequency.

(2) Here is how the experiment goes.

Racket: AT900T
String: Zymax62
Tension: main 26/cross 28
String method: One string, two knots. Sort of Gosen Haribido. Main starts in the middle, goes toward each side, at 26lb. Then one side continue cross up, first cross is at 26lb, then 28lbs, last five top cross back to 26lb. The other side goes down at 26lbs.

The picture below shows the tension / frequency changes over time. Horizontal is hours, vertical is the frequency, and converted tension. Blue line shows when the racket is not in use, red line is the hours being used for games.

This result only apply to this particular racket/string/tension condition. Others may perform differently. However, the trend should be similar.

#1

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interesting. i have been doing some investigation on tension vs. frequency too.

a side comment though, last time i strung a Carlton with ZM62 @ 22lbs. i get 1135Hz. which is significantly higher than the frequency this person has recorded, which is kinda odd.

however, another data point that i gathered seems to agree with his. on BG65, each pound of tension corresponds to around 25Hz difference. so each time i increase tension by one pound, the frequency goes up by around 25Hz. i assume this will be different for different string but will be very similar.

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3. ### keith.roche Regular Member

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I would like to chime in with my experience,...

Frequency would change with respect to the length and thickness of the string as well as the material used. So it would be different for every string, but might be similar for strings with the same diameter, from different brands.

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Several factors will cause the discrepancy, such as 1) My tension may not be accurate, or my 27lb is lower than your 27lbs. 2) The way of how the sound is generated (I simply hit the center of the string with another racket 3) How the sound is recorded (I used a MP3 player) 4) The racket frame may contribute something different....

As I said, this result only apply to this racket/string/tension combination. Only the trend is a good indication how the tension will change relatively over time.

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5. ### milford30 Regular Member

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does it even make sense to say the tension drops from 27 to 24 in 2 days with approx 4 hours of play?

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badder, i agree with all points.

i just broke the ZM62 on my ARC10 earlier tonight, i plan to restring it with ZM62 again. i will do the same experiment as you so we can compare data.

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btw, how are you measuring the fundamental frequency? i am using my iphone with a frequency analysis app call iAnalyzerLite. i do a similar thing, i ping the string bed with my hand and then it records and shows the frequency spectrum of the ping. i pick out the fundamental frequency from the plot.

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8. ### jerby Regular Member

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a 2 lbs drop in 24 hours is roughly what you'd expect. Try string 2 rackets, identically right after each other. So there's about half an hour to an hour difference, And allready, just in a hour you can hear the difference.

However, "27lbs" or "24bs" are just numbers to me. I never play with string the first day and they usually last me at least a week. So if my 27 "is really only 23lbs" that's fine with me. because what everybody else calls 23 would then "really only be 20lbs".

But my interest in peaked, I want to measure some of this stuff myself

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i don't have full data yet. but here are a few more unknowns we can measure.

firstly, my ARC10 was strung with ZM62 at 23.5lbs. i didn't measure the frequency then, but i have measured it before it broke, it was 1060Hz. if i string it up against at 23.5lbs, then we can tell how much it loss tension. we can compare it with badder's findings.

another issue is that the nature of the string material might have changed over time as it is being plastic deformed. i will try to measure the frequency of a new and a old ZM62 and then compare the frequency, then we know if new or used string are different or not.

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I recorded the sound in WAV format, and used free frequency analyzing software to pick up the fundamental frequency. I think any software will work fine, such as yours. The difference here is that I hit the entire string bed with another racket. If you ping the string like playing a guitar, then the string boundary condition will be different from my situation. In another word, your string may be "short" and my is more like an average of the whole string bed, that may be the reason your frequency is higher than what I got, because assume everything else are the same, short string generate high frequency.

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Last edited: Jul 30, 2010

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The problem is that I don't have two identical racket, and I use flying clamp, so it's hard to stringing two identical ones for comparison. Hope someone could do it.

This makes perfect sense and it's real. When two people talk about the same tension, in fact they most likely talk about two different tension.

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12. ### Udonming Regular Member

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From the chat, seems like the tension stabalized after 72 hours, true ?

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13. ### keith.roche Regular Member

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not really...

thicker string makes lower frequency while thinner strings make higher...
IF; both strings are at same tension.

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14. ### silentheart Regular Member

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1) depend on the string thickness and material. given the same materiel, thinner string will have higher freq. given the same thickness, the stiffer string will have higher freq.
2) i am guessing the person in badmintoncn.com uses a crank machine. while kwun uses wise tension head. that will give you almost 2 lb difference. also if you use pre-stretch function, that will give you another lb difference.
3) here, i will suggest to ask master kwun to experiment on zymax string with different thickness and tension since zymax has the same material and construction.

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I assume everything else are the same, meaning the same string

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ZM62 @ 23.5lbs. 1171Hz.

will keep updating the frequency as time goes on.

previously the same racket and string at the same tension was at 1060Hz after 2 months of light use.

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1163Hz @ 1 hour.

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seems to have settled around 1145Hz after 24+ hours.

will let it sit for another 2 days. i am playing in Tuesday evening.

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Is this equivalent to about 1lb drop in tension?

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20. ### Andy05 Regular Member

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The stretch of the string is important, when a smash is performed it will add significantly more pressure and stretch to the string than time alone.
Soo
1) Could you play a match as soon as possible after stringing and then check the tension?
2) Could you play a match after the string has settled to its lowest tension and then check the tension?

This is an interesting topic, I like Biomechanics and that sorta thing...

#20