ISO 23351-1 Class A means DS,A ≥ 30 dB, tested to the standardised protocol by an accredited laboratory. All Class A products are tested to the same methodology. However, the actual DS,A figure within Class A varies — the class includes all products from 30 dB to approximately 40+ dB. HIGHKA’s 35 dB and Framery’s 30 dB are both Class A, but HIGHKA’s is 5 dB higher. When comparing Class A products, always ask for the specific DS,A figure, not just the class designation.