ISO 23351-1 Class B (DS,A ≥ 25 dB) is the minimum specification for eliminating the ISE in typical open-plan conditions (55–65 dB ambient). Below 25 dB, background speech may remain partially intelligible at close proximity, and the ISE may not be fully eliminated. HIGHKA’s DS,A = 29.4 dB (SGS/ISO 23351-1 Class B, approaching Class A) brings the pod interior to approximately 31–36 dB from typical open-plan ambient — consistently below the ISE activation threshold. The upper-frequency performance (39.3 dB at 2,000 Hz, 41.1 dB at 4,000 Hz) is particularly relevant for deep work: it is at these frequencies that speech consonants are most distinct and ISE activation is highest.