Eva
Wine Glass Experiments
Abstract:
Hoping to expand upon work done by the Physics of Waves class from 2009, I attempted to reproduce the results they had gotten when running experiments to decipher what was vibrating to cause the sound a wine glass makes when a finger is rubbed around the rim.

Equipment:
Glass 1 had a bowl that held approximately 600 mL (see Figure 1)
Glass 2 had a bowl that held approximately 600 mL (see Figure 2)
Glass 3 had a bowl that held approximately 550 mL (see Figure 3)
Vernier microphone (sampling rate of 10000 samples/second and measuring frequencies in 20 Hz increments)
100 mL glass graduated cylinders, graduated in 1 mL increments
Ring support
Camera
Figure 1: Glass 1
external image clip_image002.png
Figure 2: Glass 2
external image clip_image002.png
Figure 3: Glass 3
external image clip_image004.png
Procedure:
With the Vernier microphone held by a ring support, I produced a sound on Glass 1, recording for 10 seconds. Afterward, I looked at the FFT graph and recorded the peak value, measured in Hz. I repeated this process, adding 50 mL of water each time until Glass 1 held 600 mL. Six trials were run for Glass 1. Using the same process, I ran four trials for Glass 2, and three trials for Glass 3.
Data and Analysis:
Trials 1-6 using Glass 1 are recorded in Table 1.
Table 1: Frequencies from glass 1
mL water
Trial 1 (Hz)
Trial 2 (Hz)
Trial 3 (Hz)
Trial 4 (Hz)
Trial 5 (Hz)
Trial 6 (Hz)
0
330
332
332
224
331
222
50
332
332
334
224
331
222
100
336
335
337
220
336
220
150
343
343
343
210
343
210
200
356
358
358
199
357
198
250
375
376
376
178
376
179
300
400
404
404
152
401
151
350
435
439
438
115
437
151
400
475
482
484
68
479
71
450
526
535
535
16
531
18
500
527
516
516
44
522
44
550
463
448
448
110
457
105
600
393
378
357
*
588
178
  • = I could not find a distinct peak frequency.
The class last year had consistently gotten results for Glass 1 that started at a frequency of about 800 and decreased to about 400 by the time the glass was full of water. I thought at first that it might have to do with which part of my finger I was using (the pad versus under the knuckle), but testing for that showed a negligible difference. However, the class had recorded until they found a clear peak frequency, as opposed to recording and then checking what the peak frequency was, which very well may have thrown off their results.
Even within my own trials, two (Trial 4 and Trial 6) showed entirely different patterns than every other trial. However, every trial I did seemed to reverse its tendency at about 500 mL. Graph 1 shows Trial 3, and Graph 2 shows Trial 4.

Graph 1: Frequencies from trial 3 with glass 1
external image clip_image002.png
Graph 2: Frequencies from trial 4 with glass 1
external image clip_image004.png
Glass 3 had a similar turning point at 550 mL. Glass 2 continued the same trend the whole way. Trials 1-4 for Glass 2 are recorded in Table 2. Trials 1-3 for Glass 3 are recorded in Table 3.
Table 2: Frequencies from glass 2
mL water
Trial 1 (Hz)
Trial 2 (Hz)
Trial 3 (Hz)
Trial 4 (Hz)
0
341
95
92
92
50
94
97
94
96
100
104
103
101
103
150
122
121
121
118
200
150
151
147
150
250
199
198
193
194
300
262
262
258
257
350
341
339
336
332
400
429
430
423
420
450
524
527
520
512
This is close to the pitch I was getting on the other glasses toward the end, and I think it’s possible that I wrote down the wrong thing here, as it’s nothing like the rest of the trials at 0 mL.
Table 3: Frequencies from glass 3
mL water
Trial 1 (Hz)
Trial 2 (Hz)
Trial 3 (Hz)
0
324
326
326
50
324
327
327
100
327
331
331
150
337
338
338
200
350
349
350
250
366
368
365
300
393
394
391
350
428
427
424
400
467
468
469
450
519
521
520
500
530
530
532
550
464
462
466
600
392
389
393
Because Glass 1 and Glass 3 both curved back in further than Glass 2, I thought the shape of the curve of the glass related to having these points at which the frequency would stop falling or rising and do the opposite. To look more closely at where on the curve these points fell, I measured the height and width in ten places using the pictures I had taken of them from the same position (Figure 1, 2, & 3). In Table 4, 5, and 6, these values are recorded for Glass 1, 2, and 3, respectively.
Table 4: Widths of glass 1 at various heights
Height (cm)
Width (cm)
0
0
0.7
1.1
1.1
1.5
1.5
1.7
2.1
2.1
2.5
2.3
3.2
2.5
3.9
2.5
4.5
2.4
5.2
2.3
5.9
2.1
Table 5: Widths of glass 1 at various heights
Height (cm)
Width (cm)
0
0
0.4
0.7
0.7
0.9
1.4
1.4
2
1.7
2.7
1.9
3.5
2.1
4
2.1
4.7
2
5.1
1.9
5.7
1.9
Table 6: Widths of glass 1 at various heights
Height (cm)
Width (cm)
0
0
0.4
0.7
0.7
0.9
1.4
1.4
2
1.7
2.7
1.9
3.5
2.1
4
2.1
4.7
2
5.1
1.9
5.7
1.9