Sound generated when a cup of water is hit

In summary, the frequency of the sound generated by hitting a glass beaker remains the same regardless of the force used, and can be considered as the natural frequency of the system. Changing the density of the liquid will only affect the amplitude of the vibration, not the frequency. When hitting an empty cup, the cup's surface and the air column inside will vibrate at different frequencies, and filling the cup with water will dampen the vibration of the cup's surface but not alter its frequency. The sound heard is a superposition of different frequencies, affected by the force used to hit the glass.
  • #1
nairsgame
3
0
Hello

I have some questions regarding the following problem:

Imagine I have a glass beaker partially filled with water. Assume that I were to hit the beaker (say at the top edge to be specific) with a noodle stick. Assume that I do not hit again until the vibrations have completely died down.

Question#1: Will the frequency of the sound generated be the same every time? Or does it vary with the force with which I hit?

Question#2: If the frequency in #1 were to remain same always, Can I consider this as the natural frequency of that system?

Question#3: Assume that I were to change the density of the liquid (but keep the length of the air column above it same). Can the frequency be different from above? Or will only the amplitude change due to damping?

Thanks
Game
 
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  • #3
Thank you Bobbywhy!

That answers my question

Thanks
Game
 
  • #4
I have some more question on this:

1. when I hit an empty cup, is the cup's surface vibrating at a different frequency compared to the air column inside the cup? If so, will I be able to detect 2 sets of frequency one inside the cup and another outside the cup along it's sides?

2. When I fill it partially with water, does part of the cup above the water level vibrate at a different frequency than one below it? Or does water just dampens the vibration and not alter the vibrating characteristics of the cup?

3. When I partially fill the cup with water, like in Q#1 above, will I be able to detect 3 different frequencies ?

4. Does a partially filled cup actually work somewhat similar to a stringed instrument? i.e. does the water surface act similar to how we vary the length of the string in a stringed instrument when held lightly

Thanks
Game
 
  • #5
The sound you hear is basically generated by the cup's wall which can move freely and exactly as in the case of a string instrument its frequency depends on the length vibrating. The liquid of course vibrates too (as well as your finger pressing the string of a violine) but it does not affect too much the sound. The sound is actually a superposition of different frequencies and this defines its characteristic "timber". The frequency composition can be analyzed by Fourier transforming the waveform. The strength with which you hit the glass generally does not affect too much the main frequency but it does change the relationship between the amplitudes of the different frequencies and therefore it affects the timber (check it yourself next time you are having a glass of wine).
 

Related to Sound generated when a cup of water is hit

1. How does the sound of a cup of water being hit occur?

When a cup of water is hit, the force from the impact causes the water to vibrate. This vibration then creates sound waves that travel through the air and reach our ears, allowing us to hear the sound.

2. Why does the sound change when hitting the cup with different objects?

The sound produced when hitting a cup of water can vary depending on the object used and the force of the impact. This is because different objects have different densities and shapes, which can affect the way the water vibrates and the resulting sound waves.

3. Why does the sound of the cup hitting the water seem louder when close to it?

When we are close to the cup of water, the sound waves have less distance to travel before reaching our ears. This means that the sound reaches us more quickly and with less attenuation, making it seem louder compared to when we are farther away from the cup.

4. Can the amount of water in the cup affect the sound produced?

Yes, the amount of water in the cup can affect the sound produced when it is hit. This is because the water's surface tension and the size of the water's surface area can change, which in turn affects the way the water vibrates when hit and the resulting sound waves.

5. Is there a difference in the sound produced when hitting a plastic cup versus a glass cup?

Yes, there can be a difference in the sound produced when hitting a plastic cup versus a glass cup. This is because glass and plastic have different material properties, such as density and stiffness, which can affect the way the cup vibrates and the resulting sound waves.

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