A new metric to quantify and evaluate low frequency impact noise

ABSTRACT Low frequency footfall noise ("thudding") is a common source of complaints in lightweight (timber) joistframed multifamily projects. Previous work by the authors has indicated that the low frequency impact sound pressure levels (LFISPL) from a standard ISO tapping machine are highly correlated with occupant reaction. It remains to translate the raw LFISPL data into a useful single number metric that maintains the high correlation with subjective reaction, provides adequate dynamic range to distinguish the performance of different assemblies, and is conveniently scaled. This paper introduces Low-frequency Impact Rating or LIR, a new metric to quantify and evaluate low frequency impact noise

Modeling a representative room to explore standard sound measurement methods for ASTM Impact Sound Rating testing

ASTM ISR (Impact Sound Rating) test method suffers from non-reproducibility problems, especially in lower frequency bands in smaller rooms where the sound field is non-diffuse. The problem arises from the fact that Sound Pressure Level is measured in these rooms, which is dependent on the room dimensions if the sound field is non-diffuse due to low modal density. Currently, this non-diffusivity is ignored leading to non-reproducibility issues. In this work, we explore the ASTM standard discrete method, ISO discrete method, and the ISO corner method for sound measurement. We also explore the sound power computation using intensity measurements and the diagonal microphone measurement method. This initial work will be followed by exploring more simulation methods and real world testing on practical structures

Guidelines to measure low-frequency floor impact performance with high reproducibility

The impact performance of a floor-ceiling assembly is calculated as a single number rating using the ASTM standard but this method suffers from high measurement variability due to a non-diffuse sound field, especially in low-frequencies. The same assembly tested by different engineers can get different results. This work is part of a large project undertaken by the authors to develop a new measurement method for floor-ceiling impact noise performance with an improved reproducibility in low frequencies. A simulation model was used to guide a new measurement method based on the reciprocity principle. Different types and shapes of assemblies were simulated and the learnings were used to develop measurement guidelines with a standard deviation of 1 - 1.5 dB, a significant improvement from the existing variation of 4 - 10 dB. In the future, the proposed guidelines would be tested in real structures

Exploring Reciprocity method to measure radiated sound during a standard impact test

The existing standard measurement method to obtain the performance of a floor-ceiling assemblies for footstep noise suffers from several problems, especially the non-reproducibility due to room modes at low-frequency one-third octave bands, and the lost information on the input force. This makes it difficult to evaluate and compare one floor-ceiling assembly with another. In this work, we are exploring an alternate approach to obtain a frequency response function based measurement of a floor ceiling assembly by using a speaker as an input source and acceleration as a measured response. For a simulation model and for a concrete structure tested for this work, this reciprocity method showed great success when compared to a force input and a microphone response frequency response function

Expression and purification of recombinant human inward rectifier K+ (KCNJ) channels in Saccharomyces cerevisiae

The inward rectifier family of potassium (KCNJ) channels regulate vital cellular processes including cell volume, electrical excitability, and insulin secretion. Dysfunction of different isoforms have been linked to numerous diseases including Bartter's, Andersen-Tawil, Smith-Magenis Syndromes, Type II diabetes mellitus, and epilepsy, making them important targets for therapeutic intervention. Using a family-based approach, we succeeded in expressing 10 of 11 human KCNJ channels tested in Saccharomyces cerevisiae. GFP-fusion proteins showed that these channels traffic correctly to the plasma-membrane suggesting that the protein is functional. A 2-step purification process can be used to purify the KCNJ channels to >95% purity in a mono-dispersed form. After incorporation into liposomes, (86)Rb(+) flux assays confirm the functionality of the purified proteins as inward rectifier potassium channels