Musical Water Glasses: Sound science while making music

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Making music using just a couple of household items is a great rainy-day science experiment to talk about vibrations and resonance!

Musical water glasses teaches children about resonance and how our ears and brains interpret sounds through vibration. It’s a hands-on learning experience where your child can be 100% involved!

Not only will this experiment teach about scientific principles, but it will also incorporate music and the opportunity to talk about musical notes.

How to make the Musical Water Glasses science experiment

Supplies you will need

For the Musical Water Glasses experiment, you’ll need the following:

Glasses
Water
Measuring cup

Here’s a fun kid’s book about the five senses to accompany this experiment!

Before you start

It could get messy if the water spills, so be sure to have a towel handy or place it under the experiment.

Also, since you are using glass, keep a watchful eye on your child during this experiment.

Instructions

Here is how to do the Musical Water Glasses science experiment:

Step 1: Fill your water glasses

In “Mary Had a Little Lamb”, we have four musical notes. Those notes equate to these levels of water in our glasses (you may have to make adjustments):

Note 1: 1.25c
Note 2: 1.5c
Note 3: 1.67c
Note 4: 0.34c

Get your child involved: Have your child pour the measured water into each glass, noticing that each glass has different amounts of water (this knowledge will come in handy in a minute!).

Step 2: Dip your finger into water

If you do not want to use the water in your musical glasses for fear of spilling something, grab a second small container specifically for dipping your fingers.

Step 3: Rub the rim of the glasses

It may take a few passes on the rim of the glass to start hearing a sound, but it will happen!

Play with the amount of pressure that you apply if you do not hear results right away.

Note that some small children might have trouble applying the right amount of pressure and consistency to make the glass sing.

If that’s the case (and you’re comfortable with it), you can have your child tap the side of the glass with a small object. We used an ink pen with a rubber finger rest and tapped the side with the rubber.

Step 4: Play your song

To play “Mary Had a Little Lamb”, you will play in this order:

Note 3
Note 2
Note 1
Note 2
Note 3 (3 times)
Note 2 (3 times)
Note 3
Note 4 (2 times)
Note 3
Note 2
Note 1
Note 2
Note 3 (4 times)
Note 2 (2 times)
Note 3
Note 2
Note 1

Get your child involved: To help your child understand that we are creating vibrations that our ears and brains interpret as music, have them touch the side of the glass (where there is no water) when you make it sing. Do they feel the vibration?

The science behind the Musical Water Glasses experiment

The Musical Water Glasses experiment teaches:

Resonance
How musical glasses work
Making different tones

How it works

The human ear and brain interpret sound by their vibration, and different vibrations equate to different sounds.

How do you achieve different vibrations? Through the level of water in our glasses!

Resonance

A formal definition of resonance is a reinforcement of sound (as a musical tone) in a vibrating body or system caused by waves from another body vibrating at nearly the same rate.

In our experiment, when we rub the glass, we are causing the glass to vibrate. That secondary vibration transmits into a sound that we hear in this experiment.

How musical glasses work

When you rub your moistened finger along the rim of the glass, you are creating vibrations along the walls of the glass and the air around the glass. Your finger needs to be moistened because, without it, there would be far too much friction for your finger to glide along the rim of the glass.

Those vibrations create a sound wave with a specific frequency, based on the level of water in the glass.

Those vibrations change with varying levels of water in the glass.

Making different tones

As mentioned, the tones you can create with glasses depend on the amount of water that is in the glass.

If you have more water in the glass, the volume of air is less, causing a lower tone.

The less water you have in the glass, the higher the volume of air, and that results in a higher tone.

That’s how we can make songs using these glasses: by varying the amount of water in each glass, we can create notes for a song. The more notes you need for the song, the more glasses you will need for the experiment.

Questions to ask while experimenting

What do you think it will sound like when we take out water from the water glass?
What will happen if we do not wet our fingers first before making a sound with the glass?

More physics experiments to try out with your child

FAQ about the Musical Water Glasses physics experiment

Why do glasses filled with different amounts of water make different sounds?

These glasses make a sound because we are causing the glass to vibrate. That vibration is picked up by our ears and translated into a musical note. When a glass has more water in it, it is heavier. A heavier glass requires more energy to vibrate than an empty glass, which propagates a sound wave more slowly, which causes a lower frequency (note). When there is less water, the opposite happens, causing a higher pitch.

Will only crystal glasses sing?

The most common glass to use for musical glasses (or the “glass harp”) is the wine glass. But really, the glass must simply have a stem on it to produce sound. Others have used cognac glasses with short stems to produce sound as well.

In order to get the reverberating sound that is common with the glass harp, the glass must be made of crystal. Glass will make a clunkier sound than crystal.