5.1 Providing speech privacy in open-plan spaces depends upon many factors, the most significant of which are the following: (1) the shadow zone of part-height space dividers and the diffraction of sound from the edges of space dividers; (2) the primary sound reflective properties of the ceiling system; (3) the level of masking sound present in the space; and (4) the distance between speaker and listener. Guide E1374 provides additional detail on the factors contributing to speech privacy in open-plan spaces.

5.2 In this test method the third factor, masking sound, is eliminated and the fourth factor, the distance between speaker and listener, is standardized for all specimen types. For the measurement of ceiling systems, the first factor, the shadow zone, is also standardized for each divider height used. Experience has indicated that results obtained by this test method may not fairly represent the speech privacy that may be achievable with non-flat ceiling systems. For the measurement of furniture panels used as acoustical barriers, the second of these factors, the sound reflectance of the ceiling, is standardized. For the measurement of reflective and absorptive vertical surfaces used as wall finishings or furniture panels, the first and second factors are standardized and all paths between the speaker and listener reflecting only off of the ceiling are eliminated.

5.3 This test method provides standardized techniques to assess the contribution of specific components of an open-plan space. The test method specifies an acoustical testing environment for each component type that isolates its contribution from the contribution of other components, which may in actual open-plan environments contribute significantly to the overall speech privacy.

5.4 The significance of test results obtained by this test method must also be considered with regard to the attainable measurement accuracy. The attainment of speech privacy in the presence of masking sound is critically dependent upon sound level of the speech relative to the masking sound; a change as small as 2 dB in either the speech or masking sound may change the privacy from significant to insignificant. The normally accepted test accuracies for sound attenuation measurements may be inadequate to evaluate components having marginal interzone attenuation performance for open-office needs.

1.1 This test method covers the measurement of the interzone attenuation for three components of open-plan spaces:

1.1.1 Ceiling systems when used in conjunction with partial-height space dividers. This arrangement is commonly used in offices to achieve speech privacy between work zones in the absence of full-height partitions. This test method is applicable to any ceiling configuration, including, for example, a pattern of sound-reflective panels in an otherwise sound-absorptive ceiling. This test method generally requires use of a fixed space divider height of 1.50 m [5 ft]. In recognition of trends toward alternate divider heights in open office environments, measurements with an alternate divider height may be conducted in accordance with this standard.

1.1.2 Furniture panels used as acoustical barriers in open-plan spaces to provide speech privacy or sound isolation between working positions.

1.1.3 Vertical panels, including wall finishes such as sound-absorbent panels, and furniture panels or screens which may reflect sound. It may not be applicable to such items as window finishes or furniture other than panels if these differ significantly from flat wall panels.

1.1.4 The combination of results from the various components of an open-plan office is beyond the scope of this standard.

1.2 The values stated in either SI units or inch-pound units are to be regarded separately as standard. The values stated in each system may not be exact equivalents; therefore, each system shall be used independently of the other. Combining values from the two systems may result in non-conformance with the standard.

1.3 Unless otherwise qualified, all dimensions specified in this test method shall be understood to have a tolerance of ±6 mm (±¹/₄ in.) The values stated in SI units are to be regarded as the standard. The values given in parentheses are provided for information only.

1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.