Question

The figure given shows the images of sound waves. Look at them and answer the following question.

Which sound is noise?

• A. $a$
  
• B. $d$
  
• C. $c$
  
• D. $b$
  

Answer 1

Answer: (B)

A musical sound is periodic and regular, but noise is irregular and non-periodic. Both are mixtures of sounds of different frequencies but frequencies in musical sound are discrete but noise frequencies are discontinuous and irregular.

In a musical sound, wave patterns are repeating whereas a noise has irregular wave patterns. As out of the given figure, we have irregular patterns in figure $\left(d\right)$, so it is a noise.