ISO 23351‑1 classifies acoustic pods into five grades: A+ ( ≥ 35 dB), A ( 30–34.9 dB), B ( 25–29.9 dB), C ( 20–24.9 dB), and D ( 15–19.9 dB). Classes A+, A and B deliver effective speech privacy in typical commercial office environments (40–65 dB ambient noise). Classes C and D provide noise reduction but cannot reliably achieve full speech privacy. For most commercial open‑plan applications, Class B (minimum ≥ 25 dB) is the minimum appropriate specification.