The Science of Music
Part 1: If I pour a certain amount of water into one glass, and less into another (of the same shape and size), then when tapped, the first glass will generate a lower pitch than the second.
Part 2: If I have two glasses with the same amount of water (or none at all), but they are of different sizes, then the smaller one will generate a higher pitch than the larger one.
In case, for whatever reason, you cannot access my report, I've included it here:
The Science behind “Singing Glasses”
The Science of Sound
Sound is made of vibrations. A leaf being blown around by wind creates sound. A piano generates sound when a key hits a string, causing it to vibrate. When the sound waves reach our ears, they delicately move the skin of the eardrum around and cause it to vibrate. “Frequency” of the sound wave (often called pitch) means how often the object vibrates, or more accurately, frequency is the amount of times that a sound wave repeats itself. The more something vibrates, the higher the frequency. Similarly, less vibrations mean lower frequency.
The science of sound applies to any musical instrument of which singing glasses are discussed in this report. Singing glasses are a group of glasses containing water, partially or in full, that can generate a range of sounds when rubbing a dampened finger along the rim of the glass or tapping it with a metal object. Depending on the size of the glass and the amount of water that it contains, vibration occurs at a certain frequency or pitch. The more water in the glass, the lower the pitch. This is because the water makes it harder for the glass to vibrate; thus, the glass vibrates less. When there is a lower water level, however, the glass will vibrate more. On the other hand, different glass sizes vibrate at different frequencies; the smaller a glass is, the more it vibrates. Therefore, a smaller glass creates a higher pitch whereas larger glasses make lower frequencies. Comparably, thickness affects the frequency of glasses. A thinner glass will vibrate more than a thicker one, consequently creating a higher pitch.
More about pitch
Pitch is measured in Hertz (Hz). One Hz is equal to one cycle per second. When Middle C on a piano is pressed, it causes the string to vibrate approximately 262 times per second, meaning that it generates a pitch of about 262 Hz. Our ears cannot detect all pitches. According to DK Find Out, “Human ears cannot detect very low-pitched noises, known as infrasound, or very high-pitched noises, called ultrasound.” The lowest and highest pitches we can hear are 20 Hz and 20,000 Hz respectively. Animals, on the contrary, can hear a wider range of frequencies than us.
Here is a link to my slideshow: https://docs.google.com/presentation/d/1dZFjEk39fzqH3F72cGBkvQJfPRD17oZcn6qTxSReJmY/edit?usp=sharing
Part 1: water levels of glasses
Part 2: shapes and sizes of glasses
Part 3 (playing a piece): both
Materials: two glasses of the same size, water, spoon
Procedure: I first laid out my materials and tapped the metal spoon against both empty glasses. They generated the same pitch. I then filled one glass up with water, but not the other; it created a lower pitch. Next, I filled the other glass with water, but only halfway; its frequency reduced, but was still higher than that of the other glass. Finally, I filled the half-full glass all the way up, like the other cup. They generated the same pitch.
Materials: two empty glasses of different sizes, spoon
Procedure: I tapped both glasses with the spoon, and noticed that the smaller one had a higher pitch.
- The glasses generated the same pitch when they were empty/contained the same amount of water.
- The glass with less water had a higher frequency.
- The smaller and thinner glass generated a higher pitch than the larger and thicker one.
The amount of water a glass contains affects its pitch; the more water in the glass, the lower the pitch. Similarly, lower water levels cause higher pitches. However, not only do water levels affect the glass' frequency, so do size and thickness; two glasses may be of the same size but the frequency of the thicker one is lower, because thinner glass will vibrate more. Or, perhaps the glasses have an identical thickness but contrasting sizes. The larger one will make a lower pitch, as it cannot vibrate as much as the smaller one. Another scenario is one where the larger glass is thinner than the smaller one. Depending on their sizes/thicknesses, they may have the same pitches, although that is rather unlikely.
From the above analysis, we can conclude that smaller, thinner, and emptier water glasses vibrate more than larger, thicker, and more full ones, thus creating a higher tone.
In the future, when I try to make music with singing glasses (which I definitely will), I can apply what I've learned about frequency/pitch/Hz, and how various water levels, thicknesses, and sizes of the glass affect it.
Sources Of Error
- I may have used slightly different glass thicknesses without knowing it.
- Perhaps a glass I used was manufactured incorrectly, therefore creating a pitch it shouldn't have.
- I did not have access to a tuner, so I couldn't hit certain notes exactly, although I was pretty much spot on for the most part.
- I needed to create a certain note, but no matter what I tried, it did not sound right (the glasses were either too big/small or thin/thick to make an A flat; the only way I could generate it was with a small glass jar that doesn't sound as musical as the cups).
- Maybe I identified a pitch incorrectly, although that is highly unlikely (as I have "absolute pitch", a rare gift most commonly among musicians, which allows me to identify a note without any reference whatsoever; studies have shown that those with absolute pitch—also called "perfect pitch"—are always 100% accurate when it comes to creating/playing/identifying/distinguishing/etc. musical notes).
"Human ears cannot detect very low-pitched noises, known as infrasound, or very high-pitched noises, called ultrasound." https://www.dkfindout.com/uk/science/sound/pitch/
I would like to thank the Calgary Youth Science Fair Society (CYSFS), for organizing this event. I would also like to thank my school's science fair coordinator, Mrs. Friesen, for all the valuable information she passed down to us. Finally, thanks to my parents—Dad for being Grammarly 2.0 and Mom for recording my presentation. I couldn't have done any of this without you.