【国外标准】 Standard Classification for Determination of Low-Frequency Impact Noise Ratings

4.1 The purpose of the LIR rating is to describe the low-frequency impact noise, often referred to as “thudding,” primarily generated by footfall on lightweight structures. The rating increases as the impact sound attenuation of the floor-ceiling structure increases. This rating has been shown to correlate with subjective reaction3,4 and can be used to evaluate and compare the low-frequency impact noise performance of assemblies.4.2 The LIIC rating can be used for relative comparison and to rank-order the low-frequency performance of assemblies within a given test laboratory.5 The reproducibility of LIIC between laboratories has not been measured, and the relationship between laboratory and field ratings (LIIC and LIR) is not assumed or established.NOTE 1: The tendency for measurement uncertainty to increase at low frequencies should be considered when utilizing metrics of classification standard.NOTE 2: This classification does not replace Classification E989 (Impact Insulation Class) and is not interchangeable with it. For example, the LIIC rating of an assembly does not determine its IIC rating and cannot be used to show compliance with an IIC requirement. The expectation is that the low-frequency ratings would be reported alongside the existing ratings.4.3 This classification shall only be used with one-third-octave-band data.1.1 This classification provides methods for calculating single-number ratings of low-frequency impact noise transmission, based on one-third-octave-band impact noise levels as described in Test Methods E492 and E1007.1.2 This classification defines ratings that are not defined in other standards. Other standards may define additional ratings based on the methods of this classification.1.3 Units—The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.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, health, and environmental practices and determine the applicability of regulatory limitations prior to use.1.5 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.