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General Knowledge

Why Sound changes while filling up a bucket with water?

Why Sound changes while filling up a bucket with water?

You might have observed that the Sound while filling up a bucket with water changes continuously as it gets filled up. Do you know the simple reason behind it?

Change of sound

The initial Sound when we start filling up a bucket with water will be of Bass (Low Frequency) and becomes Shrill (Treble – High Frequency) as it gets filled up.

Sound is a physical experience or sensation when our ears receive some vibrations. We know that the frequency of sound extends from inaudible to audible range. Below certain frequency we cannot hear the sound even if there is a vibration and so when it is high above a specific level.

Reason for change in sound

A metallic bucket (any vessel for that matter) contains full air when it is not filled with any substance. When water is filled in a metallic bucket, the metal starts vibrating, producing a sound. In addition to the metallic sound and vibration, another sound comes out of it. This is the sound due to the vibration of air column inside the bucket and above the water inside.

The frequency of the sound produced depends upon the length of Air Column. With larger air column, the frequency will be low. With shorter air column the frequency of sound will be more. In the beginning as the air column is larger inside the vessel, the frequency of the sound produced is low (Bass). As the bucket gets filled up with water, the length of air column reduces and the frequency of sound becomes high.

The vibrations and sound produced by the metal gets suppressed as water gets filled in the bucket due to the decreasing air column.

Use of this changing sound effect

The musical instrument “Jaltarang” is based on this principle of sound vibrations, which can produce a variety of musical notes.

Picture used for illustration only – Credit: Water vector created by brgfx –

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Born and brought up in Kerala, I did my schooling in Kerala and graduated (B.Sc Physics) from the Calicut University. I have worked with a Swedish Company from 1994 to 2015, as a Senior Project Manager in their Group IT Division in Dubai. This blog is the result of my strong desire to communicate with others, sharing what I know and what I could gather from various sources.


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