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Smashing Sound

Discussion in 'Techniques / Training' started by Athelete1234, Jun 6, 2007.

  1. illusionistpro

    illusionistpro Regular Member

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    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.
     
  2. stumblingfeet

    stumblingfeet Regular Member

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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.
     
  3. cheongsa

    cheongsa Regular Member

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    Do you mean the other way around? Most high-speed videos show the skirt of plastic shuttles deforming more than feather shuttles...
     
  4. cheongsa

    cheongsa Regular Member

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    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.]
     
  5. stumblingfeet

    stumblingfeet Regular Member

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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)?
     
  6. SystemicAnomaly

    SystemicAnomaly Regular Member

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    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.
    .
     
    #26 SystemicAnomaly, Jun 9, 2007
    Last edited: Jun 9, 2007
  7. stumblingfeet

    stumblingfeet Regular Member

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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.
     
  8. cheongsa

    cheongsa Regular Member

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    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...

    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.
     
  9. cheongsa

    cheongsa Regular Member

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    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...
     
  10. XtC-604

    XtC-604 Regular Member

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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 @.@
     
  11. SystemicAnomaly

    SystemicAnomaly Regular Member

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    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.
     
  12. SystemicAnomaly

    SystemicAnomaly Regular Member

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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.

    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.
     
  13. Slicedbanana07

    Slicedbanana07 Regular Member

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    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.
     
  14. fsnicolas

    fsnicolas Regular Member

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    My, my... all this physics just for getting satisfaction from the sound of a shuttlecock. :D
     
  15. Shifty

    Shifty Regular Member

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    i simply think that a quick, more explosive action generates a louder bang as the force is compressed more. for those with a larger swing, the it usually sounds less loud as the time span is longer, meaning less force per time but same force in total as it's a longer time frame. so i think maybe your friends hit it with a very fast action, whereas you hit it with a slower, more lengthened shot.
     
  16. XtC-604

    XtC-604 Regular Member

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    Well, i don't think the thread starter is that much of a recreational player or intermediate......
     
  17. XtC-604

    XtC-604 Regular Member

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    Btw i think its cause your slicing your shot
     
  18. SystemicAnomaly

    SystemicAnomaly Regular Member

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    the thread starter is a 14-yr old who uses nylon shuttles & describes self as an intermediate. he has indicated that he duznt believe that he is slicing the shuttle -- maybe he is, maybe not.
     
  19. Matt

    Matt Regular Member

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    Maybe he is not hitting the shuttle straight on. Still, even if you do, the crack does not come out every single time, even if you were using a feather – more like a ping or somewhere between a ping and a crack.

    The strings resilience would also have something to do with it as well.
     
  20. XtC-604

    XtC-604 Regular Member

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    Matt, are you in BC right now?i played with Azn 123 today, lets play next week if your in town
     

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