The standard tapping machine is the most widely used sound source to measure impact noise. The fivehammers hitting at afrequencyof2Hz each are usually modelled as one hammer acting at afrequencyof10Hz. Starting with the experimental finding that measured velocity spectra exhibit ac lear 2Hzl ine spectrum, an analytical calculation model is derivedtodetermine the sound power emitted by afive hammer configuration into infinitely large reception plates. The experimentally found 2Hzline spectrum can be partly explained by runtime effects of the bending wavesoriginating from an assembly of fivepoint sources. Even more influential are the deviations between real tapping machines and the ideal tapping machine as described in ISO standard 10140. Fort he description of real tapping machines, measured impact velocities and time histories of the impacts could be used. These data are available at PTB from conformity tests with tapping machines. The conclusion is that real standard tapping machines emit a2H zl ine spectrum which enables measurements down to the 50 Hz one-third octave band with an acceptable uncertainty. PACS no. 43.55. n, 43.58 e
A method to measure the impact sound reduction at a compact measurement setup (COMET) is developed at the Physikalisch-Technische Bundesanstalt. This paper presents the setup and the test procedure with respect to a physical model of impact sound reduction for locally reacting floor coverings. The impact sound reductions of many floor coverings obtained at different test facilities according to ISO 10140 and obtained at different COMETs are compared. Under consideration of the standard uncertainties, an alternative procedure to calculate the impact sound reduction at the COMET is proposed which is different to the procedure in the current version of the standard describing the COMET (ISO/DIS 16251-1).
The influence of static pressure and temperature on sound reduction indices, impact sound pressure levels, improvements of impact sound pressure levels and sound reduction indices, and relative installation noise levels is investigated. Theory revealed a systematic influence on sound reduction index and normalized impact sound pressure level. Firstly, the sound power radiated by a vibrating structure is directly proportional to the sound impedance in air and therefore to static pressure and temperature to the power of −0.5. Secondly, the sound pressure produced in a room by a sound source also depends on sound impedance, i.e. on static pressure and temperature. Since the excitation of a test specimen is not influenced by static pressure or temperature, the two effects are not compensated by any other mechanism, thus temperature and static pressure also influence sound reduction index and normalized impact sound pressure level. Experimental verification involved measurement of sound reduction index in a small test suite at static pressures between 307 and 970 hPa. Measurement results for single-shell structures showed the expected behaviour, whereas results for double-shell structures revealed a considerable scatter with a tendency towards even larger temperature and static pressure influences. For comparison of the acoustic properties of building elements, it is therefore advisable to introduce a normalized sound reduction index and a normalized impact sound pressure level, with both referred to reference conditions of static pressure and temperature. Improvements in impact sound pressure levels and sound reduction index, and relative installation noise levels are determined from changes in sound level differences. Since each difference is influenced in the same manner by meteorological conditions, the resulting improvement is independent of static pressure and temperature, as long as the differences were determined under the same meteorological conditions.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.