What should be minimum distance between listener and reflecting surfac

1.	What should be minimum distance between listener and reflecting surface ?
Answer» <html><body><p>28m <br/><a href="https://interviewquestions.tuteehub.com/tag/18m-280488" style="font-weight:bold;" target="_blank" title="Click to know more about 18M">18M</a> <br/>19m <br/>`16.6m` </p>Solution :Is same sound is heard after time `t ge (1)/(10)` s <a href="https://interviewquestions.tuteehub.com/tag/due-433472" style="font-weight:bold;" target="_blank" title="Click to know more about DUE">DUE</a> to reflection then it is called an <a href="https://interviewquestions.tuteehub.com/tag/echo-11626" style="font-weight:bold;" target="_blank" title="Click to know more about ECHO">ECHO</a> (because sensation of hearing <a href="https://interviewquestions.tuteehub.com/tag/lasts-2782602" style="font-weight:bold;" target="_blank" title="Click to know more about LASTS">LASTS</a> for `(1)/(10)s` in human <a href="https://interviewquestions.tuteehub.com/tag/ears-964179" style="font-weight:bold;" target="_blank" title="Click to know more about EARS">EARS</a>). Thus, `t _(min) = (1)/(10) s=0.1 s` <br/> Now, when sound is reflected from reflector at distance x from its source and echo is heard at the end of t time. <br/> `v = (2x)/(t) implies x = (vt)(2) implies x_(min) = (v)/(2)xx t _(min)` <br/> `therefore x_(min) = (332)/(2) xx 0.1 = 16.6 m`</body></html>

What should be minimum distance between listener and reflecting surface ?