1{
2 "title": "Steel sheet gong: how the parameters shape the sound",
3 "intro": "Each section varies one property of the simulated sheet or of the excitation while everything else stays at the simulator defaults: a 12 by 18 inch, 22 gauge (0.79 mm) stainless steel sheet hanging in portrait orientation with a 3 mm bow across its width, heard 1 m in front of its center, recorded for 4 s. The clips are computed with the simulator's default numerical settings (8 mm grid), so the 'Open in simulator' links reproduce them exactly. Click a player to hear a clip. Every clip is rendered at the simulator's default playback level (+20 dB relative to 1 Pa at full scale, with the same soft clipper), so loudness differences within and between sections are the ones the model predicts, and a clip sounds as it does in the app. The numbers under each clip are the peak pressure and sound pressure level at the listener, the RMS pressure over the clip, the spectral centroid of the sound between 0.2 and 1.2 s (a measure of brightness), and fitted 60 dB decay times of a low and a high band.",
4 "sweeps": [
5 {
6 "id": "strike-speed",
7 "title": "Drumstick: stick speed",
8 "text": "A wooden stick tip (30 g effective mass) strikes the sheet at 70 percent of its width and 35 percent of its height. Speed sets both the loudness and the character: the contact force grows with speed, the contact shortens, and more energy reaches the high modes. In these clips the peak level rises from about 87 dB at 0.5 m/s to 109 dB at 6 m/s, and the spectral centroid from about 190 Hz to 1.6 kHz, so the sound grows brighter as well as louder.",
9 "base": {
10 "excitation": "strike"
11 },
12 "param": "strikeVelocity",
13 "unit": "m/s",
14 "values": [
15 0.5,
16 1,
17 2,
18 3,
19 4.5,
20 6
21 ]
22 },
23 {
24 "id": "strike-mass",
25 "title": "Drumstick: stick mass",
26 "text": "The same speed with a lighter or heavier stick. A light stick gives a short contact and a bright tap. A heavier stick stays in contact longer, which by itself favours the low modes, but it also pushes the sheet further, and the extra energy reaches the high partials through the nonlinearity. In these clips the two effects roughly cancel between 10 and 60 g, and the 120 g stick is both the loudest and the brightest of the set. The peak contact force changes little with the mass (about 180 N at 10 g and 230 N at 120 g), because the local response of the sheet limits it.",
27 "base": {
28 "excitation": "strike"
29 },
30 "param": "stickMass",
31 "unit": "g",
32 "scale": 0.001,
33 "values": [
34 0.01,
35 0.03,
36 0.06,
37 0.12
38 ]
39 },
40 {
41 "id": "strike-stiffness",
42 "title": "Drumstick: tip hardness",
43 "text": "The Hertz contact stiffness K stands for the hardness of the tip. A soft (rubber or felt) tip has a low K and a long, gentle contact that excites mainly the low modes: the softest tip here is about 17 dB quieter than the default and has almost no energy above 2 kHz. A hard tip (dense wood, or a metal beater) has a high K and a larger contact force, which makes the strike louder; in these clips the brightness does not increase further beyond the default value.",
44 "base": {
45 "excitation": "strike"
46 },
47 "param": "contactStiffness",
48 "unit": "N/m^1.5",
49 "values": [
50 5000000.0,
51 50000000.0,
52 500000000.0,
53 5000000000.0
54 ]
55 },
56 {
57 "id": "strike-position",
58 "title": "Drumstick: strike position",
59 "text": "Where the sheet is struck decides which modes are excited: a strike at the center excites only modes that are symmetric about both axes, while a strike near an edge or a corner excites the twisting and edge modes as well. The central strike is the loudest and the lowest of the four, since it drives the low symmetric modes that radiate best; the off-center default is the brightest.",
60 "base": {
61 "excitation": "strike"
62 },
63 "clips": [
64 {
65 "label": "center",
66 "params": {
67 "strikeFracX": 0.5,
68 "strikeFracY": 0.5
69 }
70 },
71 {
72 "label": "off-center (default)",
73 "params": {
74 "strikeFracX": 0.7,
75 "strikeFracY": 0.35
76 }
77 },
78 {
79 "label": "near the right edge",
80 "params": {
81 "strikeFracX": 0.95,
82 "strikeFracY": 0.5
83 }
84 },
85 {
86 "label": "near a corner",
87 "params": {
88 "strikeFracX": 0.92,
89 "strikeFracY": 0.08
90 }
91 }
92 ]
93 },
94 {
95 "id": "push-amount",
96 "title": "Push and release: push amount",
97 "text": "The corner is pushed by a given amount, held until the sheet settles, and released over 20 ms. A larger push stores more energy and, because the stiffness rises with deflection, produces a stronger pitch glide and a stronger transfer of energy to the higher partials. The 2 and 5 mm pushes are nearly linear and very quiet, with most of their sound below 100 Hz; the 20 mm push is about 10 dB louder than the default and has far more energy above 500 Hz.",
98 "param": "pushAmount",
99 "unit": "mm",
100 "scale": 0.001,
101 "values": [
102 0.002,
103 0.005,
104 0.01,
105 0.02
106 ]
107 },
108 {
109 "id": "push-sign",
110 "title": "Push and release: with or against the bow",
111 "text": "The sheet has a 3 mm bow across its width. Pushing the corner in the direction of the bow and against it are not equivalent: the shell stiffness is asymmetric, so the two cases have different low-mode frequencies and a different wobble. Here the push against the bow gives a quieter and lower sound, with about 20 dB less energy between 500 Hz and 2 kHz.",
112 "clips": [
113 {
114 "label": "+10 mm (with the bow)",
115 "params": {
116 "pushAmount": 0.01
117 }
118 },
119 {
120 "label": "-10 mm (against the bow)",
121 "params": {
122 "pushAmount": -0.01
123 }
124 }
125 ]
126 },
127 {
128 "id": "push-release",
129 "title": "Push and release: release time",
130 "text": "How fast the finger lets go. An instantaneous release is a step in force and excites every mode, giving a click that is about 24 dB louder at its peak than the default; a release over tens of milliseconds excites only the lowest modes, as a fingertip does, and the 50 ms release brings the centroid down to about 100 Hz.",
131 "param": "releaseTime",
132 "unit": "ms",
133 "scale": 0.001,
134 "values": [
135 0,
136 0.005,
137 0.02,
138 0.05
139 ]
140 },
141 {
142 "id": "bow-amplitude",
143 "title": "Sheet: initial bow (push and release)",
144 "text": "Real sheet metal has a bow of a few millimetres, which makes it a shallow shell with an asymmetric stiffness. A flat plate has a symmetric, purely hardening nonlinearity; the bowed sheet moves energy out of the inaudible sub-50 Hz range into the audible partials and produces the slow wobble of a real sheet. In these clips the flat plate and the 1.5 mm bow are about 8 dB quieter than the 3 mm bow, and the centroid rises with the bow.",
145 "param": "bowAmplitude",
146 "unit": "mm",
147 "scale": 0.001,
148 "values": [
149 0,
150 0.0015,
151 0.003,
152 0.006
153 ]
154 },
155 {
156 "id": "bow-amplitude-strike",
157 "title": "Sheet: initial bow (drumstick strike)",
158 "text": "The same sweep excited by the default drumstick strike (30 g at 3 m/s) instead of the corner push. The trend reverses: struck, the flat plate rings brightest, and the 6 mm bow gives the dullest sound, with about 10 dB less energy above 2 kHz than the default, presumably because the curvature couples the bending motion to the in-plane motion and its loss. The peak pressure is the same in all four clips, since the impact itself sets it.",
159 "param": "bowAmplitude",
160 "unit": "mm",
161 "scale": 0.001,
162 "values": [
163 0,
164 0.0015,
165 0.003,
166 0.006
167 ],
168 "base": {
169 "excitation": "strike"
170 }
171 },
172 {
173 "id": "bow-shape",
174 "title": "Sheet: shape of the bow (push and release)",
175 "text": "The same 3 mm sag as a bow across the width, across the height, or as a dish curved both ways. With the push at a corner, the bow across the width gives the loudest and brightest sound and the bow across the height the lowest.",
176 "clips": [
177 {
178 "label": "across the width",
179 "params": {
180 "bowShape": "width"
181 }
182 },
183 {
184 "label": "across the height",
185 "params": {
186 "bowShape": "height"
187 }
188 },
189 {
190 "label": "dish",
191 "params": {
192 "bowShape": "dish"
193 }
194 }
195 ]
196 },
197 {
198 "id": "bow-shape-strike",
199 "title": "Sheet: shape of the bow (drumstick strike)",
200 "text": "The same sweep excited by the default drumstick strike (30 g at 3 m/s) instead of the corner push. The bow across the height again gives the lowest sound (a centroid near 460 Hz against 650 Hz for the bow across the width), while the peak pressure is the same for all three.",
201 "clips": [
202 {
203 "label": "across the width",
204 "params": {
205 "bowShape": "width"
206 }
207 },
208 {
209 "label": "across the height",
210 "params": {
211 "bowShape": "height"
212 }
213 },
214 {
215 "label": "dish",
216 "params": {
217 "bowShape": "dish"
218 }
219 }
220 ],
221 "base": {
222 "excitation": "strike"
223 }
224 },
225 {
226 "id": "thickness",
227 "title": "Sheet: thickness (push and release)",
228 "text": "Bending stiffness grows with the cube of the thickness while mass grows linearly, so a thicker sheet has higher mode frequencies. The same 10 mm push, however, is a smaller multiple of the thickness, which weakens the nonlinear transfer of energy to the higher partials, and in these clips this effect wins: the sound becomes lower and purer with thickness even though the individual modes rise. Gauges 24, 22, 18 and 14.",
229 "param": "h",
230 "unit": "mm",
231 "scale": 0.001,
232 "values": [
233 0.0006,
234 0.00079,
235 0.0012,
236 0.002
237 ]
238 },
239 {
240 "id": "thickness-strike",
241 "title": "Sheet: thickness (drumstick strike)",
242 "text": "The same sweep excited by the default drumstick strike (30 g at 3 m/s) instead of the corner push. Struck, the trend is the opposite: the stick meets a stiffer sheet with a shorter, harder contact (the peak contact force rises from about 170 N at 0.6 mm to 700 N at 2 mm), so the thick sheets are louder and much brighter.",
243 "param": "h",
244 "unit": "mm",
245 "scale": 0.001,
246 "values": [
247 0.0006,
248 0.00079,
249 0.0012,
250 0.002
251 ],
252 "base": {
253 "excitation": "strike"
254 }
255 },
256 {
257 "id": "size",
258 "title": "Sheet: size (push and release)",
259 "text": "Plate dimensions (width by height) at the same thickness. Mode frequencies scale with the inverse square of the size, so a larger sheet is lower and slower, and under the same 10 mm push it also stores less energy and sounds quieter. The 24 by 36 inch sheet is an extreme case: its lowest modes lie near 10 Hz, below hearing, and most of its peak pressure is this infrasound, so it sounds much fainter than its sound pressure level suggests.",
260 "clips": [
261 {
262 "label": "8 x 12 in",
263 "params": {
264 "Lx": 0.2032,
265 "Ly": 0.3048
266 }
267 },
268 {
269 "label": "12 x 18 in (default)",
270 "params": {}
271 },
272 {
273 "label": "18 x 24 in",
274 "params": {
275 "Lx": 0.4572,
276 "Ly": 0.6096
277 }
278 },
279 {
280 "label": "24 x 36 in",
281 "params": {
282 "Lx": 0.6096,
283 "Ly": 0.9144
284 }
285 }
286 ]
287 },
288 {
289 "id": "size-strike",
290 "title": "Sheet: size (drumstick strike)",
291 "text": "The same sweep excited by the default drumstick strike (30 g at 3 m/s) instead of the corner push. Struck, the larger sheets are louder and lower, the 18 by 24 inch sheet reaching about 105 dB at its peak against 100 dB for the smallest; the 24 by 36 inch sheet again puts much of its energy below 100 Hz.",
292 "clips": [
293 {
294 "label": "8 x 12 in",
295 "params": {
296 "Lx": 0.2032,
297 "Ly": 0.3048
298 }
299 },
300 {
301 "label": "12 x 18 in (default)",
302 "params": {}
303 },
304 {
305 "label": "18 x 24 in",
306 "params": {
307 "Lx": 0.4572,
308 "Ly": 0.6096
309 }
310 },
311 {
312 "label": "24 x 36 in",
313 "params": {
314 "Lx": 0.6096,
315 "Ly": 0.9144
316 }
317 }
318 ],
319 "base": {
320 "excitation": "strike"
321 }
322 },
323 {
324 "id": "outline",
325 "title": "Sheet: outline at equal area (push and release)",
326 "text": "Four outlines cut from the same amount of steel (216 square inches, the area of the default 12 by 18 inch sheet): the rectangle, a square, the ellipse of the same 2:3 proportions, and a circle. Everything else stays at the defaults, including the 3 mm bow across the width. The push acts at a corner for the rectangle and the square and at the rim point opposite the hole for the ellipse and the circle, and this changes the excitation as much as the outline changes the modes: the rim of an ellipse is stiffer than the corner of a rectangle, so the same 10 mm push deforms the whole sheet instead of bending a corner, stores more energy, and makes the ellipse and the circle about 10 dB louder than the rectangle and the square. The square is lower and purer than the rectangle, with about 8 dB less between 500 Hz and 2 kHz; the circle is the purest of the four, and the ellipse keeps the most energy above 2 kHz.",
327 "clips": [
328 {
329 "label": "rectangle 12 x 18 in",
330 "params": {}
331 },
332 {
333 "label": "square 14.7 x 14.7 in",
334 "params": {
335 "Lx": 0.37338,
336 "Ly": 0.37338
337 }
338 },
339 {
340 "label": "ellipse 13.5 x 20.3 in",
341 "params": {
342 "shape": "ellipse",
343 "Lx": 0.34392,
344 "Ly": 0.51587
345 }
346 },
347 {
348 "label": "circle 16.6 in",
349 "params": {
350 "shape": "ellipse",
351 "Lx": 0.42113,
352 "Ly": 0.42113
353 }
354 }
355 ]
356 },
357 {
358 "id": "outline-strike",
359 "title": "Sheet: outline at equal area (drumstick strike)",
360 "text": "The same four outlines excited by the default drumstick strike (30 g at 3 m/s), at the same fraction of the width and height in every case. With the excitation now the same, the peak levels agree to within half a decibel and the differences are in the timbre: the rectangle is the brightest (centroid about 650 Hz), the circle by far the darkest (about 280 Hz) with a strong low band, and the square and the ellipse lie in between. The square and the circle also put more energy below 100 Hz than the two elongated shapes.",
361 "base": {
362 "excitation": "strike"
363 },
364 "clips": [
365 {
366 "label": "rectangle 12 x 18 in",
367 "params": {}
368 },
369 {
370 "label": "square 14.7 x 14.7 in",
371 "params": {
372 "Lx": 0.37338,
373 "Ly": 0.37338
374 }
375 },
376 {
377 "label": "ellipse 13.5 x 20.3 in",
378 "params": {
379 "shape": "ellipse",
380 "Lx": 0.34392,
381 "Ly": 0.51587
382 }
383 },
384 {
385 "label": "circle 16.6 in",
386 "params": {
387 "shape": "ellipse",
388 "Lx": 0.42113,
389 "Ly": 0.42113
390 }
391 }
392 ]
393 },
394 {
395 "id": "ellipse-size",
396 "title": "Ellipse: size (push and release)",
397 "text": "Elliptical sheets inscribed in the same bounding boxes as the rectangular size sweep above, pushed 10 mm at the rim. Unlike the rectangles, which get quieter as they grow, the ellipses get louder with size up to 18 by 24 inches, because the rim push loads the whole sheet. The 12 by 18 inch ellipse is much the brightest of the set, with a centroid above 500 Hz; the larger ellipses are lower and purer, and the 24 by 36 inch sheet again puts most of its energy below 100 Hz, where its lowest modes are barely audible.",
398 "base": {
399 "shape": "ellipse"
400 },
401 "clips": [
402 {
403 "label": "8 x 12 in",
404 "params": {
405 "Lx": 0.2032,
406 "Ly": 0.3048
407 }
408 },
409 {
410 "label": "12 x 18 in",
411 "params": {}
412 },
413 {
414 "label": "18 x 24 in",
415 "params": {
416 "Lx": 0.4572,
417 "Ly": 0.6096
418 }
419 },
420 {
421 "label": "24 x 36 in",
422 "params": {
423 "Lx": 0.6096,
424 "Ly": 0.9144
425 }
426 }
427 ]
428 },
429 {
430 "id": "ellipse-size-strike",
431 "title": "Ellipse: size (drumstick strike)",
432 "text": "The same sweep excited by the default drumstick strike (30 g at 3 m/s). The trend matches the rectangles: larger ellipses are louder and lower, the 18 by 24 inch sheet reaching about 104 dB at its peak against 100 dB for the smallest, while the centroid falls from about 750 Hz at 12 by 18 inches to about 300 Hz at 24 by 36 inches.",
433 "base": {
434 "shape": "ellipse",
435 "excitation": "strike"
436 },
437 "clips": [
438 {
439 "label": "8 x 12 in",
440 "params": {
441 "Lx": 0.2032,
442 "Ly": 0.3048
443 }
444 },
445 {
446 "label": "12 x 18 in",
447 "params": {}
448 },
449 {
450 "label": "18 x 24 in",
451 "params": {
452 "Lx": 0.4572,
453 "Ly": 0.6096
454 }
455 },
456 {
457 "label": "24 x 36 in",
458 "params": {
459 "Lx": 0.6096,
460 "Ly": 0.9144
461 }
462 }
463 ]
464 },
465 {
466 "id": "ellipse-bow-amplitude",
467 "title": "Ellipse: initial bow (push and release)",
468 "text": "The 12 by 18 inch ellipse with a flat shape and with bows of 1.5, 3 and 6 mm across the width, pushed 10 mm at the rim. The bow matters more for the ellipse than for the rectangle: the peak level rises by about 15 dB from the flat plate to the 6 mm bow (9 dB for the rectangle), and the sound turns from a low, pure ring into a bright one, with the energy above 2 kHz rising by about 30 dB between 1.5 and 6 mm.",
469 "param": "bowAmplitude",
470 "unit": "mm",
471 "scale": 0.001,
472 "values": [
473 0,
474 0.0015,
475 0.003,
476 0.006
477 ],
478 "base": {
479 "shape": "ellipse"
480 }
481 },
482 {
483 "id": "ellipse-bow-amplitude-strike",
484 "title": "Ellipse: initial bow (drumstick strike)",
485 "text": "The same sweep excited by the default drumstick strike (30 g at 3 m/s). As for the rectangle, the trend reverses under the strike: the flat ellipse rings brightest (centroid above 900 Hz) and the 6 mm bow gives the dullest sound, about 10 dB weaker above 2 kHz, while the peak pressure is the same in all four clips.",
486 "param": "bowAmplitude",
487 "unit": "mm",
488 "scale": 0.001,
489 "values": [
490 0,
491 0.0015,
492 0.003,
493 0.006
494 ],
495 "base": {
496 "shape": "ellipse",
497 "excitation": "strike"
498 }
499 },
500 {
501 "id": "ellipse-bow-shape",
502 "title": "Ellipse: shape of the bow (push and release)",
503 "text": "The same 3 mm sag on the 12 by 18 inch ellipse as a bow across the width, across the height, or as a dish curved both ways. The bow across the width gives the loudest and brightest sound; the bow across the height is about 5 dB quieter and much purer, with almost nothing above 2 kHz; the dish is as loud as the width bow but less bright.",
504 "base": {
505 "shape": "ellipse"
506 },
507 "clips": [
508 {
509 "label": "across the width",
510 "params": {
511 "bowShape": "width"
512 }
513 },
514 {
515 "label": "across the height",
516 "params": {
517 "bowShape": "height"
518 }
519 },
520 {
521 "label": "dish",
522 "params": {
523 "bowShape": "dish"
524 }
525 }
526 ]
527 },
528 {
529 "id": "ellipse-bow-shape-strike",
530 "title": "Ellipse: shape of the bow (drumstick strike)",
531 "text": "The same sweep excited by the default drumstick strike (30 g at 3 m/s). The peak is the same for all three; the width bow is the brightest (centroid about 750 Hz against 500 Hz for the other two), and the dish puts the most energy below 100 Hz.",
532 "base": {
533 "shape": "ellipse",
534 "excitation": "strike"
535 },
536 "clips": [
537 {
538 "label": "across the width",
539 "params": {
540 "bowShape": "width"
541 }
542 },
543 {
544 "label": "across the height",
545 "params": {
546 "bowShape": "height"
547 }
548 },
549 {
550 "label": "dish",
551 "params": {
552 "bowShape": "dish"
553 }
554 }
555 ]
556 },
557 {
558 "id": "material",
559 "title": "Sheet: material (push and release)",
560 "text": "Stainless steel, aluminium, and brass at the same thickness. The mode frequencies scale with the square root of E over rho, which is nearly the same for steel and aluminium but about 30 percent lower for brass, so the brass sheet sounds lower and, under the same push, about 7 dB quieter. The loss parameters are kept fixed, although real materials differ there too.",
561 "clips": [
562 {
563 "label": "stainless steel",
564 "params": {}
565 },
566 {
567 "label": "aluminium",
568 "params": {
569 "E": 69000000000.0,
570 "nu": 0.33,
571 "rho": 2700
572 }
573 },
574 {
575 "label": "brass",
576 "params": {
577 "E": 100000000000.0,
578 "nu": 0.34,
579 "rho": 8500
580 }
581 }
582 ]
583 },
584 {
585 "id": "material-strike",
586 "title": "Sheet: material (drumstick strike)",
587 "text": "The same sweep excited by the default drumstick strike (30 g at 3 m/s) instead of the corner push. Struck, the aluminium sheet, at about a third of the mass of the steel one, is the loudest and by far the brightest (a centroid near 1.3 kHz), and the brass sheet is the lowest.",
588 "clips": [
589 {
590 "label": "stainless steel",
591 "params": {}
592 },
593 {
594 "label": "aluminium",
595 "params": {
596 "E": 69000000000.0,
597 "nu": 0.33,
598 "rho": 2700
599 }
600 },
601 {
602 "label": "brass",
603 "params": {
604 "E": 100000000000.0,
605 "nu": 0.34,
606 "rho": 8500
607 }
608 }
609 ],
610 "base": {
611 "excitation": "strike"
612 }
613 },
614 {
615 "id": "damping-sigma0",
616 "title": "Damping: frequency-independent loss (push and release)",
617 "text": "sigma0 sets the decay of the lowest modes (T60 = 6.9 / sigma0). It stands in for everything that damps the sheet uniformly: the suspension, air drag, the material. In the clips the band below 100 Hz decays in roughly 12, 5 and 2 s (the 4 s clip cannot resolve the longest time well). A lower loss also leaves more time for the nonlinear transfer to the higher partials, so the less damped sheet is brighter as well as longer.",
618 "param": "sigma0",
619 "unit": "1/s",
620 "values": [
621 0.4,
622 1.15,
623 3.5
624 ]
625 },
626 {
627 "id": "damping-sigma0-strike",
628 "title": "Damping: frequency-independent loss (drumstick strike)",
629 "text": "The same sweep excited by the default drumstick strike (30 g at 3 m/s) instead of the corner push. The decay of the low band follows the same rule, while the brightness changes less than it does under the push.",
630 "param": "sigma0",
631 "unit": "1/s",
632 "values": [
633 0.4,
634 1.15,
635 3.5
636 ],
637 "base": {
638 "excitation": "strike"
639 }
640 },
641 {
642 "id": "damping-sigma1",
643 "title": "Damping: frequency-dependent loss (push and release)",
644 "text": "sigma1 makes the high modes decay faster, in proportion to the square of their wavenumber; it stands mainly for radiation into the air. Too little and the highs ring like a cymbal; too much and the sheet sounds dull. At the lowest value here the band above 2 kHz decays about as slowly as the low modes; at the highest it sits more than 50 dB below the 100 to 500 Hz band.",
645 "param": "sigma1",
646 "unit": "m^2/s",
647 "values": [
648 0.0001,
649 0.0005,
650 0.0025
651 ]
652 },
653 {
654 "id": "damping-sigma1-strike",
655 "title": "Damping: frequency-dependent loss (drumstick strike)",
656 "text": "The same sweep excited by the default drumstick strike (30 g at 3 m/s) instead of the corner push. Struck, the difference is more audible: the lowest value gives a long metallic ring with a centroid near 3.8 kHz, and the highest a dull thud with a centroid near 220 Hz.",
657 "param": "sigma1",
658 "unit": "m^2/s",
659 "values": [
660 0.0001,
661 0.0005,
662 0.0025
663 ],
664 "base": {
665 "excitation": "strike"
666 }
667 },
668 {
669 "id": "damping-inplane",
670 "title": "Damping: in-plane loss (push and release)",
671 "text": "The stretching modes of the sheet lie at several kilohertz and, once the sheet is curved, couple to transverse motion. Without their own loss they ring for the whole low-frequency decay. Under the push the effect on the metrics is small (the band above 2 kHz is more than 40 dB down in every case); it is mainly audible as a faint high ring late in the decay when the loss is zero.",
672 "param": "sigmaIn",
673 "unit": "1/s",
674 "values": [
675 0,
676 20,
677 100
678 ]
679 },
680 {
681 "id": "damping-inplane-strike",
682 "title": "Damping: in-plane loss (drumstick strike)",
683 "text": "The same sweep excited by the default drumstick strike (30 g at 3 m/s) instead of the corner push. Struck, the difference is plain: with no in-plane loss the stretching modes ring at several kilohertz and pull the centroid up to about 5 kHz.",
684 "param": "sigmaIn",
685 "unit": "1/s",
686 "values": [
687 0,
688 20,
689 100
690 ],
691 "base": {
692 "excitation": "strike"
693 }
694 }
695 ],
696 "gainDb": 20
697}