Question

The formation of echoes can take place when the reflecting surfaces are located at a distance greater than __________

(a) 7 m

(b) 10 m

(c) 13 m

(d) 17 m

The question was posed to me by my college professor while I was bunking the class.

This interesting question is from Common Acoustical Defects in chapter Acoustics and Ventilation of Construction & Building Materials

Answer 1

Correct choice is (d) 17 m

To explain: The formation of echoes can take place when the reflecting surfaces are located at a distance greater than 17m. This defect can be removed by making surfaces highly absorbent.