02314nas a2200277   4500008004100000022002000041245009500061210006900156260000800225300001400233490000600247520141100253653002801664653002201692653000901714653002401723653001501747653002001762653001901782653001401801100002001815700001401835700002101849700001701870856014901887       2022                        eng d  a2624599X (ISSN)00aSound Reflections in Indian Stepwells: Modelling Acoustically Retroreflective Architecture0 aSound Reflections in Indian Stepwells Modelling Acoustically Ret  cmar  a227–2470 v43 aRetroreflection is rarely used as a surface treatment in architectural acoustics but is found incidentally with building surfaces that have many simultaneously visible concave right-angle trihedral corners. Such surfaces concentrate reflected sound onto the sound source, mostly at high frequencies. This study investigated the potential for some Indian stepwells (stepped ponds, known as a kund or baori/baoli in Hindi) to provide exceptionally acoustically retroreflective semi-enclosed environments because of the unusually large number of corners formed by the steps. Two cases— Panna Meena ka Kund and Lahan Vav—were investigated using finite-difference time-domain (FDTD) acoustic simulation. The results are consistent with retroreflection, showing reflected energy concentrating on the source position mostly in the high-frequency bands (4 kHz and 2 kHz octave bands). However, the larger stepped pond has substantially less retroreflection, even though it has many more corners, because of the greater diffraction loss over the longer distances. Retroreflection is still evident (but reduced) with non-right-angle trihedral corners (80◦ –100◦). The overall results are sufficiently strong to indicate that acoustic retroreflection should be audible to an attuned visitor in benign environmental conditions, at least at moderately sized stepped ponds that are in good geometric condition.10aArchitectural acoustics10aearly reflections10aFDTD10aintangible heritage10areflection10aretroreflection10aRoom acoustics10astep-well1 aCabrera, Densil1 aLu, Shuai1 aHolmes, Jonothan1 aYadav, Manuj  uhttps://www.scopus.com/inward/record.uri?eid=2-s2.0-85129315509&doi=10.3390%2facoustics4010014&partnerID=40&md5=fa5e718a0341abf9c2075d79591ba1fb