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1.1 This classification provides a single figure rating that can be used for comparing building systems and subsystems for speech privacy purposes. The rating is designed to correlate with transmitted speech intelligence between office spaces.

1.2 Excluded from the scope of this classification are applications involving female speakers or children,2 languages other than English, and sound spectra other than speech. Thus excluded, for example, would be comparisons of building systems or subsystems for their effectiveness in reducing transmitted noise from machinery, industrial processes, bowling alleys, music rooms, places of entertainment, and the like.

1.3 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

4.1 Each weighting factor given in Table 1 represents the fraction of overall speech intelligence contained within the associated one-third octave frequency band.

4.2 The weighting factors in Table 1 are obtained by multiplying each individual one-third octave band weighting factor of ANSI S3.5-1969 by 300. Articulation class (AC) values are thus related to but distinctly different from articulation index (AI) values. In particular, the AC considers only the effect of signal attenuation; while the AI considers such additional factors as speech level and spectrum and background sound level and spectrum.