ASTM E2638-08

This test method provides a means of measuring the sound isolation between the interior of a closed room and locations outside the room, and also the background noise levels at the locations outside the room. The results can be used to rate the degree of speech privacy, or to estimate the probability of speech being intelligible or audible at each receiving point.

People speak at different levels and vary their voice level in reaction to room noise and other acoustical factors. Consequently it is not possible to say definitely whether a room is protected against eavesdropping. One can only assign a probability of being overheard. The owners or managers of the closed room under consideration must set criteria for this probability according to their specific goals and circumstances. The non-mandatory appendix gives an approach to setting criteria.

1.1 This test method describes a test procedure for measuring the degree of speech privacy provided by a closed room, for conversations occurring within the room, and with potential eavesdroppers located outside the room.

1.2 The degree of speech privacy measured by this method is that due to the sound insulation of the room structure—the walls, floor, ceiling and any other elements of the room boundaries—and to the background noise at listening positions outside the closed the room.

1.3 Potential eavesdroppers are assumed to be unaided by electronic or electroacoustic equipment, and not touching the room boundaries. Determined efforts to eavesdrop are not addressed.

1.4 The method may be applied to any enclosed room, whether specifically intended to be protected against eavesdropping or not.

1.5 The method does not set criteria for adequate speech privacy. A non-mandatory appendix provides guidance on how the results of this test method may be used to estimate the probability of an eavesdropper being able to understand speech outside a closed room, and how to set criteria for such rooms.

1.6 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.

1.7 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.