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Thread: Smashing Sound

  1. #18
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    Quote Originally Posted by kwun View Post
    i suggest you borrow your friend's racket and try it out. see if you can make it "boom" like they can.

    if so, then perhaps it is the racket/string, if not, then perhaps you don't hit like they do.
    That sounds like a good idea. I'm also looking for a replacemnt racquet for the one I broke, so I have to try around anyways
    They all have looser strings than me though. I prefer the better control I can get with higher tensions.

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    Quote Originally Posted by Athelete1234 View Post
    ...
    I think I'm just not hitting hard enough for my strings to activate properly, cause I noticed that I can get a loud bang.... if I hit really hard.
    Perhaps you are trying too much to hit it harder -- ironically this can actually be counter-productive. Try to relax your body, arm and grip a bit more & see if that helps. Oft times when a player tries to hit a 70% or 80% speed smash, they end up hitting it faster instead (kinda counter-intuitive).

    Is it possible that you area not hitting your smashes on the (longitudinal) mid-line of the stringbed -- in line with the shaft? Another possibility is that you are hitting too low in the stringbed (below the sweetspot)? You might be swinging too late for your swing speed.

    A better contact point would be approx half way between the stringbed sweetspot and the top (tip) of the frame. Try reaching up and contacting the shuttle a fraction of a second sooner -- also, your arm should be extended (but not absolutely straight -- not hyper-extended).

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    Quote Originally Posted by cheongsa View Post
    The bang sound is a mini sonic boom, so something has to move faster than the speed of sound, for a miniscule amount of time.

    My guess is that it is some part of the bird that has surpassed the speed of sound, most likely the tips of the feathers...
    This is a possibility -- much like the tip of a whip breaks the barrier for a very short time when we "crack the whip".

    Quote Originally Posted by fsnicolas View Post
    My thoughts exactly. But, inasmuch as the feathers catch a lot of air, I think it is the strong impact and sudden change of direction of the shuttle produces the impressive "bang" sound. The strings probably just resonate a slight ringing sound. My Yonex racket with "shockless" frame/grommets produce a nice ringing sound that resonates after smashes and strong clears.
    I believe that the "turn-around" time of a feather shuttle is much quicker than that of a synthetic shuttle -- the feather shuttle is travelling backward and catching extra air for a much shorter period of time than most synthetic shuttles.

    Also, feather shuttles tend to become more stream-lined (initially) when struck forcefully. This often does not happen for many synthetic shuttles. These 2 factors make it easier to accelerate a feather shuttle to a higher initial speed and easier to create the "bang' than most synthetic shuttles.

    (On the other hand, feather shuttles tend to decelerate more -- later in their flight than some/many synthetics. A lot of beginner shuttles hardly decelerate at all).

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    Quote Originally Posted by cheongsa View Post
    The bang sound is a mini sonic boom, so something has to move faster than the speed of sound, for a miniscule amount of time.

    My guess is that it is some part of the bird that has surpassed the speed of sound, most likely the tips of the feathers...
    not trying to flame but are you kidding? speed of sound is like 700 mph. the sound it just the impact, friction and what not. i really doubt theres a sonic boom goin on there.

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    Yeah, the sonic boom seems implausible. For metric guys out there, that's about 340 m/s or 1200 km/hr. The acceleration that the shuttle would have to go through, and consequently the stress of the various forces involved would be quite large, and I'm not sure whether the shuttle could survive such an impact. The feathers are fragile, after all.

    Also, plastic shuttles are much more deformable than feather shuttles. Just try squeezing one in your hand - for a given force the plastic shuttle bends much farther. Also, feather shuttles are much more brittle - squeeze too hard and you'll break the feathers. Plastic shuttles on the other hand won't break so easily, though they may be permanently deformed if you squeeze too hard.

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    Quote Originally Posted by SystemicAnomaly View Post
    Also, feather shuttles tend to become more stream-lined (initially) when struck forcefully. This often does not happen for many synthetic shuttles.
    Do you mean the other way around? Most high-speed videos show the skirt of plastic shuttles deforming more than feather shuttles...

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    Quote Originally Posted by illusionistpro View Post
    not trying to flame but are you kidding? speed of sound is like 700 mph. the sound it just the impact, friction and what not. i really doubt theres a sonic boom goin on there.
    The bang sound is the give away signature of a shock front, though I do not know enough about fluid dynamics to know whether it is necessary to exceed the speed of sound to generate one. Maybe I am wrong.

    I just tried a hand clap, which sounds like it involves a shock front. And clearly, no part of my hands ever come close to the speed of sound.

    I know that shock fronts can form in large-amplitude waves, because of the nonlinear term in the Navier-Stokes equation. Perhaps this is the origin of the bang.

    It would interesting if someone can test this, because the two scenarios: (i) sonic boom, and (ii) no sonic boom, can be distinguished experimentally. If the shock front forms in the absence of a sonic boom, there should be a detectable lag between the shuttle being struck, and the bang sound reaching its peak intensity.

    [Side remark: it is not terribly difficult to exceed the speed of sound, actually. A stiff and light beam has a very high transverse elastic wave velocity that is greater than the speed of sound in air. The time rate of change of its transverse displacement, which is how fast parts of the beam moves, is usually slower than the speed of sound, because the amplitudes of the normal modes are small. If we can either make the amplitude of the fundamental mode very large, or make the amplitudes of higher harmonics larger, we would be able to make some parts of the beam move faster than the speed of sound.]

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    Shock waves appear in transonic flow - about Mach 0.8 to 1.2. For speeds between Mach 0.3 and 0.8 (~360-960 km/h), the flow is compressible, but without shock waves. Of course, this makes no reference to the amplitude, but the common example of fluid flow is an airplane which I'm guessing is a lot louder than a feather shuttlecock.

    cheongsa: I'm not sure if I'm understanding you correctly, but are you basically saying that when you move the racquet handle, there is a delay between that movement and the movement of the racquet head given by the length of the racquet divided by the transverse elastic wave velocity?
    Is anything actually interacting with the air, or is this effect internal to the racquet (i.e. it's an expression of the speed of sound in the racquet)?

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    Quote Originally Posted by cheongsa View Post
    Do you mean the other way around? Most high-speed videos show the skirt of plastic shuttles deforming more than feather shuttles...
    My understanding is that high-speed studies have shown that the deformation of synthetic shuttles is rather ugly -- it initially becomes very distorted on a fast shot because of the nature of its construction (the skirt is all one piece & duznt change its shape in a very uniform or coherent manner).

    On the other hand, the feathers of a feather shuttle can move more independently and will move pretty much only in 2 directions -- inward to make it a bit more stream-lined (the skirt narrows uniformly) and then outward again as the shuttle continues on its path trajectory (to provide some additional braking action during its flight that is not seen, to the same degree, with many synthetic shuttles).

    The feathers do not change shape lengthwise at all whereas synthetic shuttles can do so (which can initially impair their ability to accelerate to the same top speed that a feather shuttle does).

    Granted, the deformation of a feather shuttle is not huge, but it is significant and, most inportantly, it is uniform. for this reason the initial top speed of a feather shuttle can be greater than many, not all, synthetic ones. However, the extra braking action (as the skirt widens uniformly) wll cause the feather shuttle to slow down moreso than most synthetics.

    I would imagine that a synthetic shuttle cause a greater air turbulence than a feather shuttle becuz of the manner in which each of them deforms. This can account for differences in their initial top speed.
    .
    Last edited by SystemicAnomaly; 06-09-2007 at 07:00 AM.

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    Fluid dynamics is a tricky subject.

    I agree that the feather shuttle deforms more uniformly, but the fact remains that the material stiffness of the feather shuttle is greater than that of the plastic shuttle. For a given pressure, the plastic shuttle will simply deform more than the feather shuttle. The surface area opposing the direction of motion will have a much greater effect on the magnitude of the drag than the shape characteristics.


    Besides, air turbulence doesn't always mean more drag. Think of the dimpled golf ball versus the smooth one. The dimples create more turbulence which results in less overall drag on the system.

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    Quote Originally Posted by stumblingfeet View Post
    Shock waves appear in transonic flow - about Mach 0.8 to 1.2. For speeds between Mach 0.3 and 0.8 (~360-960 km/h), the flow is compressible, but without shock waves. Of course, this makes no reference to the amplitude, but the common example of fluid flow is an airplane which I'm guessing is a lot louder than a feather shuttlecock.
    To avoid confusion, let us be sure to identify the moving object in each case.

    (1) In my initial post, I claimed that parts of the shuttle moved momentarily faster than the speed of sound. I realized later that this is not a necessary condition for the bang sound.

    (2) In my example of the hand clap, no parts of my hands ever come close to the speed of sound. I don't know enough about fluid dynamics to tell whether air within the boundary layers might be ejected at high, possibly supersonic, speeds, or that they are ejected merely at large amplitudes, forming shock fronts after they have been ejected.

    [Side remark]
    Also, are you referring only to streamlined objects in your statements above? Most objects are audible when they move through air. Unlike sound coming from the degradation of shock fronts, their sound spectrum is also peaked at discrete frequencies. A badminton racquet hisses as it is swung, because of the degradation of vortices trailing the stringbed.

    I can identify three characteristic length scales for the stringbed: (a) the gauge of the string, approximately 1 mm; (b) the interstring distance in the cross-weave, approximately 1 cm; and (c) the overall extent of the stringbed, approximately 20 cm. Using c = 340 m/s for the speed of sound, the three characteristic frequencies should be f_a = 340 kHz, f_b = 34 kHz, and f_c = 3.4 kHz.

    f_c is of course the principal frequency we hear when we swing an unstrung racquet, but f_a and f_b are both inaudible. Perhaps an experiment can be done to analyze the acoustic spectrum of a racquet swing in ultrasonic frequencies...

    Quote Originally Posted by stumblingfeet View Post
    cheongsa: I'm not sure if I'm understanding you correctly, but are you basically saying that when you move the racquet handle, there is a delay between that movement and the movement of the racquet head given by the length of the racquet divided by the transverse elastic wave velocity?
    Is anything actually interacting with the air, or is this effect internal to the racquet (i.e. it's an expression of the speed of sound in the racquet)?
    No, that was not what I was saying. My claim is: (1) if any part of the shuttle exceeds the speed of sound, a sonic boom would occur. This is most likely to occur when the shuttle is struck, which means that the peak acoustic intensity from the sonic boom would occur momentarily after the shuttle is struck; and (2) if striking the shuttle merely produces a large amplitude pulse of air, this pulse would first move outwards, to form a shock front some distance away from the origin of the pulse. The acoustic intensity of this shock front would therefore peak some time after the shuttle is struck. This time lag should be measurable.

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    Quote Originally Posted by stumblingfeet View Post
    Besides, air turbulence doesn't always mean more drag. Think of the dimpled golf ball versus the smooth one. The dimples create more turbulence which results in less overall drag on the system.
    Form drag versus skin drag...

    A shuttlecock, being a bluff object, suffers primarily from form drag. But this situation is complicated by airflow that bleeds through the space between the shafts of the feathers...

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    ok all this transonic stuff is more than my physics 11 knowledge can handle..... but i would like to say, how is it possible that if you smash as hard as you say you do, but no SOUND!? i mean everyone that i've played against, even 12 year olds can make a minor boom @.@

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    Quote Originally Posted by XtC-604 View Post
    ok all this transonic stuff is more than my physics 11 knowledge can handle..... but i would like to say, how is it possible that if you smash as hard as you say you do, but no SOUND!? i mean everyone that i've played against, even 12 year olds can make a minor boom @.@
    Sure, everyone makes a sound when they smash a shuttle. However, the sound that we are talking about here is a fairly loud, very sharp (staccato) acoustical event. It has been my experience (25+ yrs) that most recreational players (& even many intermediate players) do NOT make a sound of this quality very often. Also, this type of sound is much less common with synthetic shuttles.

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    Better choice of words: Feathers deflect, Nylon deforms.

    I would think that the feather deflection (skirt becomes narrower) would make the shuttle sleeker - more aerodynamic. Nylon shuttles become distorted upon impact (uneven wider skirt?) & somewhat after impact making them less aerodynamic very early in their smash flight.

    Quote Originally Posted by stumblingfeet View Post
    Fluid dynamics is a tricky subject.

    I agree that the feather shuttle deforms more uniformly, but the fact remains that the material stiffness of the feather shuttle is greater than that of the plastic shuttle. For a given pressure, the plastic shuttle will simply deform more than the feather shuttle. The surface area opposing the direction of motion will have a much greater effect on the magnitude of the drag than the shape characteristics.

    Besides, air turbulence doesn't always mean more drag. Think of the dimpled golf ball versus the smooth one. The dimples create more turbulence which results in less overall drag on the system.
    You probably know a bit about more about fluid dynamic, specifically aerodynamics, than do I. I see your point that air turbulence duznt always equate to more drag. Some amount or type of turbulence (coherent turbulence?) could be beneficial to the speed/distance and control of a projectile. However, wouldn't excessive or very unruly turbulence be a detriment?

    It is my belief that the synthetic shuttle experiences 2 types of deformation. The first, more detrimental, deformation occurs as the shuttle makes contact with the stringbed. This is when the nylon shuttle becomes quite distorted -- it scrunches up & loses its conical shape. The feather shuttle, due to its longitudinal stiffness does not experience very much of this type of distortion.

    Something else to consider -- since the nylon shuttle deforms more, does it lose more of less energy in the form of heat than does a feather shuttle?

    I believe that the nylon shuttle does not turn around as quickly after string contact. This is due to its construction -- probably due to its aerodynamic qualities as well as its distribution of weight. If this is true then the nylon shuttle would be flying backward for a slightly longer period than the feather shuttle -- causing it is "catch" more air. This would undoubtedly result in more form drag. This action would most likely result in somewhat less acceleration and a different sound.

    The 2nd type of deformation of the nylon shuttle experiences is similar, but significantly different, to the type of deformation that the feather shuttle. After it turns around, the skirt of the synthetic shuttle would attempt to streamline like the feather shuttle does. However, this deformation would probably be somewhat irregular (since it does not consist of individual moving parts = feathers). In light of what you have pointed out, I'm not certain if this difference in this type of deformation is a minor factor or a major factor.

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    Quote Originally Posted by Marc E View Post
    If you mean the yonex strings when you say 'bgs' then not neccessarily, bg-65 and bg-70 are the same thickness, bg-68 is thinner than both of them, bg-80 is thinner than bg-68, but bg-66 is thinner than them all.
    So you get bg-65/bg70 > bg-68 > bg-80 > bg-66.
    The thinner the string and the higher the tension the 'sharper' the smash will sound, but it also depends on the construction of the string. I find bg-65ti sounds sharper than standard bg-65 with the same tension.

    BG68's are the same thickness as BG80's. Also, bg66's, i've seen them advertised on the actual packet as 0.68 as well.

  17. #34
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    My, my... all this physics just for getting satisfaction from the sound of a shuttlecock.

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