Significance and Use
5.1 The spectrum of the noise produced in the receiving room by the standard tapping machine is determined by (1) the size and the mechanical properties of the floor-ceiling assembly, such as its weight, surface properties, mounting or edge restraints, stiffness, and internal damping; (2) the degree of flanking transmission through associated structures; and (3) the acoustical response of the receiving room.
5.2 The standardized tapping machine specified in 6.1.1 produces a continuous series of uniform impacts at a uniform rate on a floor-ceiling assembly to allow accurate and reproducible measurements of impact sound pressure levels in the receiving room. The tapping machine is not designed to simulate any one type of impact, such as male or female footsteps or to simulate the weight of a human walker. Also, measurements described in this method and ratings based on the results are restricted to a specific frequency range. Thus the subjectively annoying creak or boom generated by human footfalls on a limber floor-ceiling assembly may not be adequately evaluated by this test method.
5.3 Laboratory Test Method E492 calls for highly diffuse sound fields and the suppression of flanking sound transmission in the laboratory’s receiving room. This field test method does not allow efforts to suppress flanking. In field tests, acoustical measurements are much more uncertain than in the laboratory since a great variety of receiving room shapes and sizes are encountered in ordinary buildings. Highly diffuse fields are seldom found and the nature of structure-borne flanking transmission can vary widely. In addition, energy can be transmitted laterally away from the receiving room. The amount of lateral transmission of energy can vary significantly between buildings. Consequently, good agreement between laboratory tests and field tests on similar floor-ceiling assemblies should not be expected.
5.4 Several metrics are available for specific uses:
5.4.1 absorption normalized impact sound pressure level (ANISPL) and apparent impact insulation class (AIIC)—These metrics are intended to evaluate the performance of the floor-ceiling assembly and adjacent structures as installed (including structure-borne flanking paths). For these metrics, sound power from associated support structures are attributed to the floor-ceiling assembly. Because these are measures of the apparent performance of the nominally separating floor-ceiling, the receiving room shall be the space directly under the tapping machine. ANISPL and AIIC may be reported if the receiving room has a volume of at least 40 m3 and the smallest dimension is at least 2.3 m. In rooms of 150 m3 or greater ANISPL and AIIC may be measured and reported only if, in all frequency bands necessary to calculate the AIIC, the receiving room absorption, A2, is less than:
| where: | ||
| V | = | the volume of the receiving room, m3 |
Results are usually not identical to laboratory tests of the floor-ceiling assembly alone. Because of the uncontrollable factors mentioned in 5.1-5.3, caution must be used when using test results to predict the performance of other floor-ceiling assemblies with similar construction.
5.4.2 impact sound pressure level (ISPL) and impact sound rating (ISR)—These metrics are intended to assess the impact sound isolation as it exists at the time of the test due to the mechanical excitation of the floor-ceiling assembly by the standard tapping machine. The measurements can be performed in any space affected by the sound of the operating tapping machine. These metrics do not represent the performance of the separating floor-ceiling. They represent the impact sound isolation between the source floor and the receiving room. There are no receiving room absorption restrictions and no receiving room volume restrictions other than being sufficiently large to accommodate the microphone positions described in 11.3.
5.4.3 reverberation time normalized impact sound pressure level (RTNISPL) and normalized impact sound rating (NISR)—These metrics are intended to assess the impact sound isolation as if the receiving room had a reverberation time of 0.5 s. This reverberation time is typical of many furnished small offices and furnished residential living rooms and bedrooms. RTNISPL and NISR shall not be reported for receiving rooms of 150 m3 or larger.
Scope
1.1 This test method covers the measurement of the transmission of impact sound generated by a standard tapping machine through floor-ceiling assemblies and associated supporting structures in field situations.
1.2 Measurements may be conducted on all types of floor-ceiling assemblies, including those with floating-floor or suspended ceiling elements, or both, and floor-ceiling assemblies surfaced with any type of floor-surfacing or floor-covering materials.
1.3 This test method defines several procedures and metrics to assess either the apparent performance of the nominally separating floor-ceiling or the isolation of a receiving room from the sound produced by the operation of the tapping machine. The receiving room may be the space directly below the tapping machine or, in some cases, any separated space that receives sound from the operation of the tapping machine. The source and receiving rooms as well as the floor-ceiling system are identified and described in the test report. All measured levels and derivative single number ratings include the effect of flanking transmission. Efforts to suppress flanking are not permitted. Available measures and their single number ratings are the impact sound pressure levels (ISPL) and impact sound rating (ISR), the reverberation time normalized impact sound pressure levels (RTNISPL) and normalized impact sound rating (NISR), and the absorption normalized impact sound pressure levels (ANISPL) and apparent impact insulation class (AIIC).
1.4 The ISPL and ISR may be measured and reported between any two specific rooms or usage areas where the source room area is large enough to accommodate the tapping machine positions and the receiving room volume is sufficiently large to accommodate the microphone positions. For all other measures and ratings in this standard, restrictions such as minimum room volume or dimensions or maximum room absorption are imposed. Thus, conditions may exist that will not allow RTNISPL (NISR) or ANISPL (AIIC) to be measured.
1.5 Where a separating floor-ceiling assembly is composed of parts that are constructed differently on the receiving room (ceiling) side, it is not possible to measure the ANISPL and AIIC of the individual elements or portions of the assembly. In this situation, the measurement will be of the composite structure, not of an individual element.
1.6 Any single field measurement only represents the actual assembly tested and cannot be used alone to accurately predict how a similar assembly might perform.
1.7 The text of this standard references notes and footnotes which provide explanatory material. These notes and footnotes (excluding those in tables and figures) shall not be considered as requirements of the standard.
