Sound has long been used to obtain information about the surrounding environment, while in classical Persian literature, sound and echo predominantly serve metaphorical, epic, or mystical functions. A notable passage in Nizami’s Haft Paykar, however, describes the use of sound around a fortress rampart to locate a concealed breach. This study examines the passage from the perspectives of the history of technology and empirical architectural knowledge. This interdisciplinary, descriptive–analytical study was based on library research. The primary unit of analysis comprised verses from Haft Paykar that connect sound production, acoustic searching around the rampart, and the discovery of a breach. Selected Persian literary and technical sources were also examined to contextualize the practical use of sound for identifying concealed structural features. The analysis indicates that practical uses of sound for identifying hidden spaces are rare in the examined Persian literary corpus. In Nizami’s account, sound is not used merely as a metaphor or aesthetic device; rather, it forms part of a narrative sequence in which a sound stimulus is produced, its response is investigated around the rampart, and a concealed breach is inferred from the acoustic clue. This logic bears a conceptual resemblance to acoustic approaches in non-destructive structural assessment, where hidden discontinuities may be inferred indirectly from variations in acoustic response. Nevertheless, the text provides no evidence of modern measurement, signal recording, or quantitative analysis. Nizami’s account constitutes a notable literary representation of the functional use of sound to identify a concealed breach or space within a wall. While it cannot be considered evidence of modern acoustic testing, it provides a valuable case for investigating historical empirical knowledge and the relationship between sound, architecture, and material practice in medieval Iran.