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Thread: Smashing Sound
06-07-2007, 05:07 PM #18
06-07-2007, 06:05 PM #19
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).
06-07-2007, 06:28 PM #20
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).
06-07-2007, 08:22 PM #21
06-08-2007, 12:15 AM #22
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.
06-08-2007, 01:46 PM #23
06-08-2007, 02:06 PM #24
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.]
06-08-2007, 06:28 PM #25
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)?
06-09-2007, 07:51 AM #26
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 08:00 AM.
06-09-2007, 12:48 PM #27
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.
06-09-2007, 04:01 PM #28
(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.
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...
06-09-2007, 04:06 PM #29
06-09-2007, 04:47 PM #30
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 @.@
06-09-2007, 05:28 PM #31
06-09-2007, 06:12 PM #32
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.
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.
06-09-2007, 11:58 PM #33
06-10-2007, 02:21 AM #34
My, my... all this physics just for getting satisfaction from the sound of a shuttlecock.
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