An unusual instance of acoustic retroreflection in architecture – Ports 1961 Shanghai flagship store façade

Abstract This paper examines acoustic retroreflection from a building facade that includes an array of 255 square trihedral corner cube reflectors with edge lengths of 300 mm. The facade is investigated by field impulse response measurements in its vicinity, laboratory measurements of reflected energy distribution from a single 300 mm corner cube and an array of corner cubes, oral-binaural measurements of corner cube arrays analogous to contiguous parts of the building facade comprising 91 corner cubes, and by finite-difference time-domain (FDTD) simulation of sound reflections from sources near the building facade. Field and laboratory results show that retroreflection from the facade has a strong effect in the 8 kHz and 4 kHz octave bands, is still clearly evident in the 2 kHz band, and is weakly present in the 1 kHz band when the source is close to the facade. Oral-binaural measurements of voice support at the selected position exhibit a 14 dB/octave spectral slope peaking in the 10 kHz 1/3-octave band. FDTD simulation shows how the retroreflective spatial focus varies with frequency and position, and results generally agree with measured values from field measurements. By using these four approaches to investigate reflections from the facade, this paper documents an intriguing acoustic phenomenon that is readily experienced by pedestrians outside this building.