A community centre has a cubic hall of side 18m. Members complain that speeches delivered from the stage lack clarity because the sound "lingers" for too long.
(i) Identify any three structural or surface features of such a hall that are likely to be responsible for the excessive persistence of sound.
(ii) Propose one specific modification for each feature you identified to reduce the reverberation, citing the principle behind your choice.
(iii) Predict qualitatively how the listening experience of the audience will change after your suggested modifications are implemented.
(iv) Explain why it is not desirable to eliminate all reflections of sound inside an auditorium.