Speech Privacy

Speech privacy is the degree to which speech from one person is unintelligible to unintended listeners in an adjacent space. It is the inverse of speech intelligibility: where intelligibility design aims to maximize understanding, privacy design aims to minimize it. Speech privacy depends on the speech level at the source, the attenuation provided by the intervening path (partition, distance, screens), the background noise level at the listener, and the listener’s effort to hear. Quantified using the Articulation Index (AI), Privacy Index (PI = 1 − AI), or Speech Privacy Class (SPC) per ASTM E1130, adequate privacy in closed offices requires SPC ≥ 80 (confidential) or SPC ≥ 60 (normal). Open-plan privacy requires optimizing the ABC approach: Absorb (ceiling, screens), Block (partitions, furniture), and Cover (sound masking). Speech privacy is a critical design requirement in healthcare (HIPAA), legal offices, HR departments, and any space handling sensitive conversations.