A dual-rating method for evaluating impact noise isolation of floor-ceiling assemblies

Abstract

Impact Insulation Class (IIC), the single-number rating for evaluating the impact noise insulation of a floor-ceiling assembly, and the associated field testing ratings, are unsatisfactory because they do not have strong correlation with subjective reaction nor provide suitable detailed information for evaluation or design of floor-ceiling assemblies. Various proposals have been made for improving the method, but the data presented indicate that no single-number rating can adequately characterize the impact noise isolation of an assembly. For realistic impact noise sources and floor-ceiling assembly types, there are two frequency domains for impact noise, and the impact noise levels in the two domains can vary independently. Therefore, two ratings are required in order to satisfactorily evaluate the impact isolation provided by a floor-ceiling assembly. Two different ratings are introduced for measuring field impact isolation in the two frequency domains, using the existing impact source and measurement method. They are named low-frequency impact rating (LIR) and high-frequency impact rating (HIR). LIR and HIR are proposed to improve the current method for design and evaluation of floor-ceiling assemblies and also provide a better method for predicting subjective reaction.

Recommendation for a Standard Rolling Noise Machine

“…This is not a recent phenomenon, as criticisms of the tapping machine have existed since the very beginning [24,25]. Alternatives have been proposed [26,27,28], but nothing has been adopted. Schultz points out however, that at the time the German DIN 4110 1938 standard was made, we already knew essentially all of the same problems that we know today, yet they still decided to make the tapping machine the way that they did.…”

Measurement of low frequency impact insulation

“…There is broad agreement that frequencies below 100 Hz are important for evaluating human reaction [2]. The authors have defined a new rating for measuring low-frequency impact isolation in the field called Low-frequency Impact Rating (LIR) [1], [5]. This rating is calculated by (1) where refers to the energetic sum of the impact sound pressure levels in the 50, 63, and 80 Hz thirdoctave bands.…”

“…(1) is not arbitrary but based on the properties of human perception of low frequency sound. Because the equal loudness contours are closer together at low frequencies than high, a comparatively smaller change in level results in a larger change in loudness [1], [5]. This is quite a general phenomenon not restricted to impact or footfall noise.…”

Improved Low-Frequency Impact Insulation Class Measurements Based on Comparison Techniques

“…The test method, although a mandatory part of the building codes, has certain limitations, and several acousticians in the industry are working on these issues [1,2,[6][7][8][9]. In this section, the discussion is limited to the measurement methodology specified in the standard with the partly incorrect assumption of the modal density of the receiving room and the issues with the room decay method while measuring room absorption.…”

“…, (2)(3)(4)(5)(6)(7)(8)(9)(10) where E is the Young's modulus in Pa and is the Poisson's ratio of the test material.…”