Fill in the blank with a suitable word:

Unpleasant sounds are called (noise/chirping).

The ratio of intensities between two coherent sound sources is 4 : 1. The difference of loudness in dB between maximum and minimum intensities when they interfere in space is :

Choose the correct word from the following:
(Pleasant, Warning, Loud, Sound, Noise)
_____ sound can cause stress and hypertension.

Loud sounds are pleasant sounds.

Solve the riddle. Write the answer.

In a little crooked well,
Without any water though,
I am always there to help you,
Listen to lessons or songs,
Inserting sticks or chalk pieces,
Will only hurt you definitely.   
Who am I? 

What is noise? 

Why is it improper to use loudspeakers at night?

Sound that is loud and unpleasant is called