ISO 23351-1 Class A certification (≥30 dB speech level reduction) from an independent, accredited testing laboratory. This is the only standard that provides certified, comparable, independently verified speech privacy performance. For regulated industry compliance contexts, request the full ISO 23351-1 test report showing the measured DS,A figure — not simply a marketing claim. HIGHKA pods achieve 35 dB, certified Class A, with the test documentation available on request.