Question

A bucket kept under a running tap is getting filled with water. A person sitting at a distance is able to get an idea of when the bucket is about to be filled. What changes take place in sound to give this idea?

Answer 1

1. The pitch of the sound produced increases which makes it shriller and thus a person can tell that the bucket is about to fill.
   A familiarity with acoustics is quite important in understanding the reason behind this behavior of sound.
2. Here the bucket is assumed to be the pipe closed at one end.
3. Now, the frequency of the fundamental node produced by the bucket would be given as, $n=\frac{v}{4L}$.
4. So, the frequency is dependent upon the length of the bucket.
5. Now, as the water is being filled in, the length 'L' decreases which further increases the frequency 'n' of the sound produced, in accordance with the above relation.

Hence, the pitch of the sound produced by infalling water is also increased by this increase in frequency and the pitch will be the highest when the bucket is at the point of being completely filled.