Single-number Quantities Research Articles

Single-number values versus subjective judgment of airborne sound insulation in dwellings

There is a long history of adapting airborne sound insulation in buildings to the actual needs. A first pan-European work was published with COST Action TU0901: Integrating and Harmonizing Sound Insulation Aspects in Sustainable Urban Housing Constructions in which the differences between the sound insulation measure and the standard sound level difference were documented. Furthermore, ISO 16283-1: Field measurement of sound insulation in buildings and of building elements—Part 1: Airborne sound insulation states: Compared to DnT, R’ has a weaker connection to the subjective impression of airborne sound insulation. To investigate this relationship a simplified listening test and a computer-simulated variation studies of a synthesized airborne sound insulation were carried out. A test sound was generated from a speech, a music, and a noise signal, each of which was filtered by six frequency responses of solid structures. In a paired comparison task, 16 participants judged the loudness of the resulting 18 sounds. The results of the listening test show that perceived loudness is significantly correlated to the single number quantity DnT,w but less to the single number quantity R’w. This finding was confirmed across all signal types. Thus, the results confirm the statement in ISO 16283-1, that the single number quantity DnT,w has a stronger connection to the subjective impression of airborne sound insulation as the quantity R’w.

Correlation between sound insulation and occupants’ perception – Proposal of alternative single number rating of impact sound, Part III

Through a series of Swedish research projects carried out over twelve years, the relation between the measured impact sound insulation and the corresponding subjective rating given by residents of multi-storey apartment buildings has been studied. Previous results, based on a limited number of building cases, suggested the need to include frequencies below 50 Hz in a frequency weighted single number quantity to get a reasonable correlation with the subjective ratings.The purpose of this paper is to include an extended amount of data compared to the previous studies to secure more substantiated results. Data has been examined for 38 building cases, including a variety of lightweight and heavy constructions. More than 1200 questionnaire responses form the basis for comprehensive statistical analyses.The results confirm the conclusions of the previous parts (I, II), stating that frequencies below 50 Hz are of importance when evaluating impact sound insulation, primarily in lightweight buildings. The correlation between measured weighted single number quantities and annoyance ratings increases significantly when the frequency range is extended down to 25 Hz. The strongest correlation was obtained when evaluating the impact sound insulation, again from 25 Hz, when using the weighted single number quantity LnT,w + CI,25–2500 where the CI-term is evaluated according to ISO 717-2 amended to the extended frequency range 25–2500 Hz. It is also suggested that in the lowest one-third octave bands, 25–40 Hz, there is no need to normalize the impact sound pressure levels with respect to the reverberation time.

Subjective evaluation of floor impact noise using the tapping machine and a non-standardized source

Assessing the acoustical performance of building floor systems relies on the impact source to be utilized and on the type of floor cover used. Besides that, a reliable assessment should consider the listeners’ judgments of the sounds transmitted through floors or radiated by them. Objective ratings measured can help to foresee tenant satisfaction provided that they are well correlated with the listeners’ judgments. The main objective of this study was to compare objective and subjective evaluations, using two types of impact sources and two types of floor covers, to try and determine which objective variables could be used to predict subject evaluation and to validate the use of an alternative impact source to be used in more realistic measurements. An objective evaluation was carried out employing impact noise insulation measurements according to ISO 10140:2010, evaluating different types of floors, resilient materials, and impact sound sources (a standardized tapping machine and a calibrated tire). In the analysis of the measured samples, several parameters were evaluated according to the sound source used. Simultaneously, "sound samples" were recorded to be used in a subjective evaluation based on the judgments of 29 listeners about the Noise Annoyance and the Loudness Sensation in response to the two impact sources. The magnitude estimation method was used. Results demonstrate that tapping machine measurements correlate very well with the subjective evaluation measurements and the calibrated tire presents well-correlated results in a specific measurement set-up. In addition, linear regression analysis of the objective and subjective variables shows alternative single number quantities for ratings of impact noise insulation

A study on subjective response to heavy-weight impact sound through representative spectrum analysis: A case study in South Korea

This study aims to suggest representative spectra of heavy-weight impact sounds and subject responses. In 2004, the Korean government implemented mandatory criteria that require a minimum concrete slab thickness of 210 mm for box-frame reinforced concrete apartment houses. Spectra representative of 140 households was derived through unsupervised cluster analysis of heavy-weight impact sounds made by rubber balls and tires. As a result, the frequency spectra and single-number quantities measured from apartments constructed before the standard was applied (110–180 mm) and those of apartments built after the introduction of the standard (210 mm) were found to be different. Based on the impact sounds created by a rubber ball and a tire, a sound pressure level in the 63–125 Hz band (Spectrum 1) was dominant for apartment houses with a floor slab of 210 mm. In apartment houses with a slab thickness of 110–180 mm, a sound pressure level in the 125–500 Hz band was relatively high (Spectrum 2 and 3). A total of 108 subjects with normal hearing were asked to express their level of annoyance relative to the sounds created by the rubber ball and tire. Spectrum 1 for the rubber ball showed a lower percentage of highly annoyed (%HA) than Spectrum 2 and 3 less than 60 dB (LiA,Fmax). In Spectrum 1, the tire elicited a higher %HA compared with Spectrum 2 and 3 above 50 dB (LiA,Fmax). Five categories of heavy-weight impact sounds with different spectra are suggested based on the annoyance responses of subjects.

Effects of Wall-to-Wall Supported Ceilings on Impact Sound Insulation for Use in Residential Buildings

In Korean residential buildings, floor impact sounds were reduced over the past few decades mainly through a floating floor system. However, ceiling constructions for impact sound reduction have not been applied actively because of a lack of useful information. This study focuses on the effects of wall-to-wall supported ceilings (WSC), which are designed with construction discontinuities between concrete slabs and ceilings, and the damping caused by porous absorbers for impact sound insulation. To examine the impact sound insulation according to ceiling conditions, measurements were performed in 25 floor–ceiling assemblies. The results indicate that ceiling treatment is mostly useful in reducing the floor impact sound. The floor impact sound owing to the WSC decreased by 2–7 dB and 2–8 dB in terms of the single number quantity for the tapping machine and rubber balls, respectively, compared with representative existing housing constructions wherein ceilings were attached on wooden sticks. Furthermore, the reduction effect of the WSC appeared to be more profound when it was applied to the floor–ceiling assembly with poor impact sound insulation. Thus, the WSC can be used to enhance the impact of sound insulation of existing housings without major repairs of floor structural layers.

고무공 충격음의 우회전달에 의한 공동주택 상하층 세대에서의 바닥충격음레벨 분포

This study investigated the distribution of floor impact sound levels in the upper and lower floors of an apartment house by the flanking transmission of the sound caused by the impact of a rubber ball. The rubber ball floor impact sound was measured in 10 units (five units on the upper and lower floors based on the excitation floor) of an apartment prior to completion. The measurements indicated that the single number quantity (L

세대간 경계벽을 공유한 신한옥의 공기전달음 차단성능 평가

Purpose: The purpose of this study is to find the considerable elements that can maintain and improve the airborne sound insulation performance of partition walls between housing unit in Modern New Han-oks though field measurement(KS F 2809). Method: Following are measurement and analysis items; the comparison of single number quantities between field measurements and laboratory condition, the correlation analysis between single number quantities according to the KS standard and other evaluation indexes, elements(specimen size, receiving room volume) required for calculating the apparent sound reduction index, the sound map analysis according to the height(low, middle, high), inside and outside, separation distance from partition wall in receiving room, and so on Result: It is necessary to set the sound insulation performance standard considering the characteristics and environmental level of Han-oks, in order to secure and maintain the noise privacy of Han-oks that shares the partition wall between housing units. And, It was analyzed that it is necessary to minimize the exposure of the wooden structure of joints including the ceiling, in case of planning a partition wall for a space where noise privacy is more strongly required, such as a bedroom. And, it is necessary to minimize the size of partition wall. In consequence, it was judged that it is necessary to reduce the noise transmission path through the adjusting the size of partition wall, the layout of a space less affected by noise around the partition wall, the diversification of architectural plan, and so on.

Subjective responses between real impact sound and rubber ball im-pact sound

By the recent COVID-19 situation, people stay more time in their home and abatements on noise between neighbouring units are increasing. Heavy/soft impact sound is one of the major noise sources in high-rise apartment buildings. Standardized heavy/soft impact source is known for having the most similar physical and subjective characteristics with real impact sound such as a child running, jumping and an adult walking. The single number quantity on the rubber ball was standardized. A classification scheme for rubber ball impact sound needs to be standardized. Several studies on subjective responses were conducted on rubber ball impact sound in various situations. In this study, subjective responses on the rubber impact sound and real impact sound were compared. The subjective experiment was conducted in the listening chamber which is furnished similarly to the typical living room of Korean apartment buildings. In the experiment, rubber ball impact sounds recorded in the real apartment building and real impact sound recorded in the mock-up building were presented through a sub-woofer and multi-channel loudspeaker system. Subjective responses were collected with an 11 points SD scale.

Measurement uncertainty and unicity of single number quantities describing the spatial decay of speech level in open-plan offices

The ISO 3382-3 standard (2012) defines single number quantities (SNQs) which evaluate the acoustic quality of open-plan offices, but does not address the issue of measurement uncertainties. This study focusses on the SNQs present in this standard related to spatial decay of speech, i.e. D2S, LpAS4m and rc. The aim is to provide additional information to the limited literature on the measurement uncertainties of these SNQs by use of both analytical developments and a stochastic approach based on simulations. The accuracy of the analytical developments was studied thanks to simulations of the sound propagation within a series of offices (1 layout, 16 acoustic configurations with different screen heights and different acoustic qualities of screens and ceiling). The SNQs obtained in the simulations cover a wide range: D2S between 3.4 and 7.5 dB(A), LpAS4m between 40.6 and 51.9 dB(A) and rc between 2.5 and 14.7 m. Therefore, the simulations are representative of a broad set of acoustic qualities. Estimated uncertainties have a magnitude of 0.4 dB(A) for D2S and vary between 0.4 and 0.7 dB(A) for LpAS4m and between 0.2 and 1.5 m for rc over a measurement path comprising 7 measurement positions. The simulations also raise the question of describing the acoustic quality of an office using a single value for the indicators. The results of the simulations show that in some cases, D2S values significantly depend on the measurement path, leading to a strong increase of its measurement uncertainty if a unique value is to be considered.

Comfort Distance—A Single-Number Quantity Describing Spatial Attenuation in Open-Plan Offices

ISO 3382-3 is globally used to determine the room acoustic conditions of open-plan offices using in situ measurements. The key outcomes of the standard are three single-number quantities: distraction distance, rD, A-weighted sound pressure level of speech, Lp,A,S,4m, and spatial decay rate of speech, D2,S. Quantities Lp,A,S,4m and D2,S describe the attenuation properties of the office due to room and furniture absorption and geometry. Our purpose is to introduce a new single-number quantity, comfort distance rC, which integrates the quantities Lp,A,S,4m and D2,S. It describes the distance from an omnidirectional loudspeaker where the A-weighted sound pressure level of normal speech falls below 45 dB. The study explains why the comfort criterion level is set to 45 dB, explores the comfort distances in 185 offices reported in previous studies. Based on published data, the rC values lie typically within 3 m (strong attenuation) and 30 m (weak attenuation). Based on this data, a classification scheme was proposed. The new quantity could benefit the revised version of ISO 3382-3.

청감실험을 통한 실내에서의 저주파 소음의 단일수치평가량 제안

In this study, new single number quantities (SNQs) based on 1/3 octave band sound pressure levels and low-frequency noise criteria were proposed to evaluate low-frequency noise in indoor spaces. The suitability of the proposed SNQs (D<SUB>max</SUB> and D<SUB>sum</SUB>) was assessed through correlation analysis with other existing SNQs (L<SUB>Ceq</SUB> and L<SUB>Zeq</SUB>) and confirmed by an auditory experiment conducted for construction and air-conditioner outdoor unit noise to be infiltrated from outdoor to indoor spaces. The result showed that the proposed SNQs were highly correlated with the existing SNQs in the range of 0.81 to 0.95. The auditory experiment also revealed that the proposed SNQs had a high correlation with subjective annoyance in the range of 0.81 and 0.89 out of the total range of presentation levels, and a similar correlation with existing SNQs for each presentation level. The proposed SNQs will be able to identify the major frequency bands in terms of annoyance and help assess and establish countermeasures at the site of the low-frequency noise.

Optimized reference spectrum for rating the façade sound insulation

Objectively determined single-number-quantities (SNQs) describing the airborne sound insulation of a façade should correspond to the subjective perception of annoyance to road traffic sounds transmitted through a façade. The reference spectra for spectrum adaptation terms C and Ctr in standard ISO 717-7 (International Organization for Standardization, 2013) are not based on psycho-acoustic evidence. The aim of this study is to develop reference spectra which result in SNQs that explain the subjective annoyance of road traffic sounds transmitted through a façade well. Data from a psycho-acoustic experiment by Hongisto, Oliva, and Rekola [J. Acoust. Soc. Am. 144(2), 1100-1112 (2018)] were used. The data included annoyance ratings for road traffic sounds (five different spectrum alternatives) attenuated by the façade (twelve different sound insulation spectrum alternatives), rated by 43 participants. The reference spectrum for each road traffic spectrum was found using mathematical optimization. The performance of the acquired SNQs was estimated with nested cross-validation. The SNQs determined with the optimized reference spectra performed better than the existing SNQs for two road traffic spectra out of five and for an aggregate of the five road traffic sound types. The results can be exploited in the development of standardized SNQs.

Sound insulation of timber hollow box floors: Collection of laboratory measurement data and trend analysis

The industrialisation of timber buildings has improved strongly in recent years. When long span is required, timber hollow-box floor elements are increasingly used due to their structural performance. The aim of this paper is to assess the acoustic performance of timber hollow-box floors, determine the governing parameters and identify the corresponding trends. We collected results from laboratory measurements covering both airborne and impact sound insulation from four different laboratories covering a wide range of application. Data include the bare floor constructions and their combination with different floating floors including both lightweight solutions and hybrid solution. We performed the analysis focusing on following parameters: element stiffness, element mass per unit area, dynamic stiffness of the resilient layer, cavity filling and floating floor material. We present the collected data both frequency-dependent and as single number quantities. General trends and features are identified in the frequency-dependent diagrams. A further detailed analysis is based on the single number quantities. It includes a general relationship between element mass per unit area and given requirements for R’W + C50-5000 and L’n,w + CI,50-2500. Furthermore, diagrams are presented illustrating the dependence of impact sound insulation numbers on the cavity filling, the dynamic stiffness of the resilient layer and the type of material used for the floating floor. The additional mass in the cavity improves both airborne and impact sound insulation by minimum 10 dB. This, combined with a floating floor, allows the fulfilment of a wide range of requirements.

단일 수치 평가량이 동일한 고무공 충격음의 주파수 레벨 변화에 따른 주관적 반응 평가

단일 수치 평가량이 동일한 고무공 충격음의 주파수 레벨 변화에 따른 주관적 반응 평가

Correlations between standardised and real impact sound sources in lightweight wooden structures

This study aimed to understand the correlation between standard impact sound sources and real impact sources in lightweight floor structures. Six real impact sources (adult walking, child running, child jumping on the floor, and three objects falling) were used to be compared with standard impact sources (i.e. tapping machine and impact ball). Measurements were conducted on a lightweight timber joist floor. Impact sound pressure levels (SPLs) produced by the standard impact sources were measured on the four floor structures with or without carpet tiles. For the real impact sources, two walkers wearing socks and slippers walked at different speeds (normal and fast) along three paths, while two children ran along the three paths and jumped at four positions. Also, the SPLs generated by dropped objects were measured at five positions. Seven standardised single-number quantities (SNQs) were calculated for the tapping machine and the impact ball, while three noise ratings (LAeq, LAFmax, and LN) were also computed from the sound recordings of the real impact sources. Both the tapping machine and the impact ball showed similar frequency characteristics with the real impact sources across all the floor structures. All the SNQs for the tapping machine and the impact ball were highly correlated with the energy-based noise ratings of the adult walking and little differences were found across walking speeds and footwear. Similar tendencies were observed from other real impact sources, indicating the high correlations between the standardised SNQs of the tapping machine and the impact ball and the noise ratings.

Correlation between objective and subjective assessment of noise barriers

There are several international standards that define the way to evaluate the attenuation capacity of noise reducing devices, by single-number quantities representing airborne sound insulation and insertion loss. These two single-value ratings define the quality and performance of acoustic barriers, the former being related to intrinsic and the latter to both intrinsic and extrinsic acoustic characteristics of the devices. However, not many studies can be found on whether these objective parameters correlate to the perception of annoyance reduction.The aim of the present work is to analyze the adequacy of these objective ratings to indicate the performance of noise barriers, by comparing their values with the perception of annoyance reduction.For this purpose, ninety individuals of two different nationalities (Spanish and Portuguese) were asked to rate the perceived annoyance reduction in a listening experimental test, in which they were exposed, under controlled conditions, to several environmental noises and acoustic screened stimuli simulated by audio filters.The obtained results show a high correlation between objective ratings and subjective annoyance perception, with a better correlation being observed for insertion loss single-number parameter than for the airborne sound insulation single-number rating. Furthermore, significant differences were found depending on the gender and nationality of the respondents. The results, from this ongoing research work, may be of great interest for future acoustic barriers design.

Impact sound insulation of floating floors: A psychoacoustic experiment linking standard objective rating and subjective perception

Floating floor increases the impact sound insulation of a load bearing concrete slab but very little is known about the subjective perception of impact sounds transmitted through floating floors. A psychoacoustic experiment was conducted to answer three research questions: 1. Is there a subjective benefit to use a floating floor instead of a non-floating floor with natural impact sounds? 2. Do the standardized single-number quantities of impact sound insulation rank the floors in the same order as subjective ranking does? 3. Does the resonance frequency of the floating floor play a role in subjective perception? Four floating floors and two non-floating floors were built in a laboratory where the impact sound insulation was tested using tapping machine and rubber ball. Four natural sound types (basketball bouncing, chair moving, walking with shoes, walking with socks) were presented to the floors and recorded in the furnished room underneath. The recorded sounds were played to 30 participants who rated their annoyance. The answers to the research questions became the following. 1. Floating floor was beneficial over non-floating floor for three sound types out of four. 2. Single-number quantities did not always rank the floors according to the same order as the psychoacoustic experiment did. 3. Lower resonance frequency predicted lower annoyance for most sound types. It seems that the current objective methods of rating the impact sound insulation are not sufficiently predicting the perceived performance of floors. Our results benefit the development of floor constructions and measurement standards.

중량충격음 레벨의 주관적 인지 변화에 대한 연구: 동일한 단일수치 평가량을 갖는 충격음을 대상으로

중량충격음 레벨의 주관적 인지 변화에 대한 연구: 동일한 단일수치 평가량을 갖는 충격음을 대상으로

Sound absorbing ceiling to reduce heavy weight floor impact sound

This study aims to reduce heavy weight impact sound, changing the sound field by applying sound absorbing ceiling. Sound absorption performance is reviewed at the reverberation chamber, and the ceiling is designed to be higher than the sound absorption coefficient of a commercial base trap. As a result of applying this to apartment households, the heavy weight impact sound evaluated using a bang machine was reduced from 4.6 dB at 63Hz to 2.2 dB at 125Hz of 1/1 octave band, and the single number quantity (Li,Fmax,AW) was reduced by 3 dB. When evaluated using a rubber ball, the noise level reduced to 4.9 dB at 63Hz and to 1.8 dB at 125Hz. The single number quantity was reduced by 2 dB. When the sound absorbing ceiling and the bass trap were installed together, there was an additional reduction of 3 dB for a bang machine and 2 dB for the rubber ball. As a result of mode analysis, the sound pressure level reduced at 63–125Hz frequency range, and the uneven phenomenon was alleviated.

An annoyance-related SNQ for the assessment of airborne sound insulation for urban-type sounds.

The sound insulation provided by a certain construction element is usually presented through Single-Number Quantities (SNQs). These SNQs are global values used to summarize the sound insulation that a construction element has as function of the frequency. Although there are standardized SNQs, whose calculation is described in the ISO 717–1 and ASTM E413-16 standards, there is not enough agreement on whether these SNQs are representative of the way humans perceive.The purpose of this research is to assess the degree of correlation between the annoyance perceived by humans and the most relevant existing SNQs for a set of façade insulation elements and urban-type sound samples. Likewise, the purpose is also to evaluate whether certain frequency bands have more influence than others on the perception of annoyance. Furthermore, to propose a reference curve for the calculation of a SNQ that is representative of the annoyance perceived by humans when faced with sounds of an urban nature.To this end, a 2-alternative choice (2-AC) listening test was carried out by 119 participants. In this test, participants had to listen to stimuli in pairs and select the stimulus that was most annoying to them. The stimuli were obtained by filtering different sound samples with the sound insulation of different construction elements. In particular, five sound samples were used for this listening test: four urban-type sound samples as well as pink noise. Also, the sound insulation of six façade insulation elements was used.The results of this listening test were then analyzed using Thurstonian models and the distance measure d’ (d-prime) was obtained for each comparison. Finally, an optimized reference curve for urban-type sounds Lopt-urban was calculated based on the results of the listening test by means of a Sequential Quadratic Programming (SQP) optimization algorithm.