A sharp sound becomes a musical note in an auditorium then, it is called
A. Echo
B. Echelon effect
C. Reverberation
D. Shrillness

Hint: In musical notation a sharp sound means a sound that has a higher pitch that is also by one semitone only that is half step. Whereas a flat sound in a musical instrument is a sound of lower pitch and generally produces a soothing effect. We know that auditoriums are closed surfaces and sound made inside the auditorium usually bounces back once or twice.

Complete step by step answer:
We know that auditorium have gallery like structure that is there are stairs on which seats are there, and auditoriums are a completely closed place so whenever a sound is produced it generally bounces to and fro from the stairs and walls and reach the ears of the observer, hence regular successive echoes are formed, and these regular successive echoes may sometime produce some musical note, this effect is known as echelon effect. And if the frequency of the notes formed is within the range of human audibility then the listeners will hear only that note prominently.

So, the correct answer is “Option B”.

Note: We have to remember that the auditorium is not made of material which can completely absorb sound waves then echo will not be produced and each and every sound will be very prominent. The range of human audibility is 20 Hz to 20 kHz. A musical note is something that is very proper with pitch, amplitude, loudness and many other factors. It is usually a very soothing sound.