The ISO 23351-1 standard classifies pods by total measured noise reduction from an external source. 35 dB reduction from a 65 dB open-floor ambient brings the internal level to approximately 30 dB — below the WHO focus work threshold and quiet enough that external speech is inaudible. 25 dB reduction from the same ambient brings the internal level to approximately 40 dB — above the WHO threshold, at which external speech may still be faintly perceptible. HIGHKA’s 35 dB rating (Class A) therefore represents the performance level that delivers the full cognitive benefit of quiet workspace access, not simply a partial reduction.