Question

Lab 24 Part 2:

Materials- 2 glass bottles, metal utensil

Methods- One bottle was filled about a quarter with water. The bottle was gently tapped at the top with a metal utensil. Gradually the bottle was filled with more water and the sound was observed as it became more filled. The same experiment was done again but instead it was blown across the top to create a sound. Then a partner blew on the top of an empty bottle while a second bottle was held to my ear listening to the sound. The partner then filled her bottle halfway and the experiment was done again.

What wave property allowed you to hear noise through your bottle in step 2 of Procedure 2, and how does the sound transmit from one bottle to the other? Did the pitch sound the same as the one made by your partner?

Answer 1

The wave property that allowed you to hear noise through your bottle was the amplitude of vibration along with pitch.

The pitch of the noise made by striking a bottle get LOWER When the bottle is empty, the glass can vibrate quickly since the water is not there to push back on the glass, so with no water, you get a high pitch and vice versa.

When you tapped the empty bottles, they all made the same sound. But when you added different amounts of water, the noise changed. You probably noticed that the more water the bottle held, the lower the pitch produced. The highest pitch came from striking the bottle with the least water. Since sound waves travel through liquid, by altering the amount of water in the bottle, the sound waves is altered as well. Sound waves can also move through other liquids like juice or milk. Liquids with varying densities will produce different sounds since the sound waves travel through them in varying speeds. Likewise, different materials make different sounds.

As you blow across the open top, the air inside the bottle is set into vibration (as the air moves across the top, the pressure of the air above the bottle changes and the air inside the bottle starts to move or vibrate). The more air there is to vibrate, the lower the frequency of the vibration (or pitch). Hence the pitch will go higher.

When your partner blew on the top of an empty bottle, the sound traveled through the glass surfaces and reached a second bottle that was held to your ear listening to the sound. The pitch was lower and the frequency was way higher in this scenario, so you could hear that sound.

Definitely, the pitch is different when you tap it compared to when you blow into it. The difference occurs because you are setting different materials into vibration: The glass vibrates when you tap and the air vibrates when you blow across the opening. When the bottle is empty, the glass can vibrate quickly since the water is not there to push back on the glass, so with no water, you get a high note. When you blow, the greater the air space, the lower the pitch, just the opposite of tapping the glass.