No full-text available
To read the full-text of this research,
you can request a copy directly from the authors.
The irrelevant speech effect in multi-talker environments: Applications to open-plan offices
Abstract
Irrelevant speech from co-workers has consistently been listed as one of the major nuisances within open-plan work environments. To explore the psychoacoustic basis of the so-called irrelevant speech effect (ISE; which causes cognitive decline and increases acoustic distraction) within a multi-talker context, a series of laboratory-based experiments were run. These experiments used room acoustical simulations of various open-plan office environments within a climate-controlled chamber to test several factors relevant to the ISE. These factors included the number of simultaneously active talkers, their spatial arrangements, sound pressure levels and the semanticity of speech. The main findings thus far indicate that multi-talker speech lead to a stronger ISE than speech from a single talker, which further interacts with the overall sound level, semanticity, etc., to exhibit a more complicated effect than what has been proposed in previous studies. The effect of the number of active talkers alone suggests reconsiderations of some assumptions in the ISO 3382-3. More generally, the perception of speech “babble” seems to be affected by multiple factors in a realistic working environment. Some of our research is directly related to characterising speech babble and its function as a beneficial sound masker in multi-talker environments.
Die Arbeit mit Führungsstäben ist in der hessischen Polizei eine seit mehreren Jahrzehnten geübte Praxis. Während der Anfänge stand die operative Ebene dem Instrument jedoch kritisch gegenüber. Wie kann eine Gruppe von Menschen mit einem Entscheider an der Spitze, die überhaupt nicht am Ort des Geschehens sind, Entscheidungen zum Einsatzverlauf treffen wollen? Entscheidungsfindungsprozesse nahmen lange Zeit in Anspruch und nicht selten überholte die Lage die Stabsprozesse und damit die Entscheider. Scheinbar war die Einschätzung, Lagen sollten grundsätzlich direkt vor Ort geführt werden, die richtigere. Einen erheblichen Anteil an der Revision dieser Haltung hatte die Entwicklung eines besonderen Stabsraummodells für die Befehlsstellen der hessischen Polizei. Dieser Beitrag skizziert den Weg und die Hintergründe der Entstehung sowie die Vorteile des Modells im Hinblick auf akustische und visuelle Wahrnehmung entscheidungsrelevanter Informationen.
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.
This study aimed to investigate the associations between physical acoustic factors, job characteristics, and job satisfaction. Acoustic measurements and questionnaire surveys were conducted in 12 open-plan offices. Active noise levels (LAeq,8-hour), reverberation time (T20), and speech privacy-related measures such as D2,S and Lp,A,S,4m were measured at each office. A total of 324 employees then completed the online questionnaire surveys. The questionnaire assessed perceived speech privacy, noise disturbance, job characteristics, and job satisfaction. The measures of job characteristics involved skill variety, task identity, task significance, and autonomy. The results showed that active noise level (LAeq,8-hour) was negatively correlated with job satisfaction. Also, job satisfaction showed a negative correlation with speech privacy, whereas the relationship between job satisfaction and noise disturbance was not significant. It was also observed that the relationship between task identity and job satisfaction was moderated by the active noise level and speech privacy.
It is currently accepted that noise is one of the most important annoyance factors in open-space offices. However, noise levels measured in open spaces of the tertiary sector rarely exceed 65 dB(A). It, therefore, appears necessary to develop a tool that can be used to assess the noise environment of these offices and identify the parameters to be taken into consideration when assessing the noise annoyance. This article presents a questionnaire to be filled by people working in such environment, and a case study in different open plan offices. The majority of the 237 respondents consider that the ambient noise level in their environment is high and that intelligible conversations between their colleagues represent the main source of noise annoyance. This annoyance was significantly correlated with their evaluation of sound intensity, which could not be represented by A-weighted level measurements. Practitioner Summary: This article presents a short questionnaire aimed to evaluate the employees' comfort in an open-plan office and to propose optimal modifications of the office. Answers collected from 237 respondents showed that intelligible conversations represent the main source of noise annoyance; moreover, overall noise level is not related to this annoyance.
Open-plan office layout is commonly assumed to facilitate communication and interaction between co-workers, promoting workplace satisfaction and team-work effectiveness. On the other hand, open-plan layouts are widely acknowledged to be more disruptive due to uncontrollable noise and loss of privacy. Based on the occupant survey database from Center for the Built Environment (CBE), empirical analyses indicated that occupants assessed Indoor Environmental Quality (IEQ) issues in different ways depending on the spatial configuration (classified by the degree of enclosure) of their workspace. Enclosed private offices clearly outperformed open-plan layouts in most aspects of IEQ, particularly in acoustics, privacy and the proxemics issues. Benefits of enhanced ‘ease of interaction’ were smaller than the penalties of increased noise level and decreased privacy resulting from open-plan office configuration.
Background sounds, such as narration, music with prominent staccato passages, and office noise impair verbal short-term memory even when these sounds are irrelevant. This irrelevant sound effect (ISE) is evoked by so-called changing-state sounds that are characterized by a distinct temporal structure with varying successive auditory-perceptive tokens. However, because of the absence of an appropriate psychoacoustically based instrumental measure, the disturbing impact of a given speech or nonspeech sound could not be predicted until now, but necessitated behavioral testing. Our database for parametric modeling of the ISE included approximately 40 background sounds (e.g., speech, music, tone sequences, office noise, traffic noise) and corresponding performance data that was collected from 70 behavioral measurements of verbal short-term memory. The hearing sensation fluctuation strength was chosen to model the ISE and describes the percept of fluctuations when listening to slowly modulated sounds (f(mod) < 20 Hz). On the basis of the fluctuation strength of background sounds, the algorithm estimated behavioral performance data in 63 of 70 cases within the interquartile ranges. In particular, all real-world sounds were modeled adequately, whereas the algorithm overestimated the (non-)disturbance impact of synthetic steady-state sounds that were constituted by a repeated vowel or tone. Implications of the algorithm's strengths and prediction errors are discussed.
The Cost-Effective Open-Plan Environments (COPE) project plan identified a need to develop relationships between acoustic conditions in open-plan offices and occupant satisfaction with those conditions. Two experiments were designed to meet this need. In each experiment, participants hired from a staffing agency for one day experienced 15 different simulated ventilation noises in combination with simulated telephone conversations, and provided ratings of their satisfaction with each noise condition. Each exposure consisted of a 15-minute period of work on memory and clerical tasks, followed by 2-3 minutes to complete a questionnaire concerning satisfaction, speech intelligibility, and the characteristics of the noise. This report concerns only the questionnaire data. Memory and clerical task performance in relation to the noise conditions will be reported separately. · Experiment 1: Noise spectrum effects on satisfaction. In this experiment subjects experienced 15 different simulated noise spectra in combination with the speech from simulated telephone conversations. · Experiment 2: Noise spectrum and noise level effects on satisfaction. This experiment used three noise spectra at each of five A-weighted noise levels, for a total of 15 different noise conditions in combination with the speech from simulated telephone conversations. RES
Open-plan offices (OPOs) have been around for more than half a century now, chronicling the vicissitudes of workplace topography amongst other factors. This paper addresses one such factor – the sound environment in occupied OPOs in relation to several objective workplace parameters, using measurements in contemporary OPOs and comparisons with studies over the last 50 years. Omnidirectional and binaural sound measurements were conducted in 43 offices during typical working hours. The results describe variation in several acoustic and psychoacoustic metrics, and present statistical models that predict these metrics as a function of the number of workstations in offices. LA,eq of 53.6 dB is typical for occupied OPOs, with spectral slope of approximately −4 dB/octave. LA,eq values do not vary much over the workplace parameters studied (e.g., floor plate area, work activity, etc), except for −2.7 dB and −4.1 dB differences between offices with/without carpeting, and offices with ceiling absorption but with/without carpeting, respectively; most likely from reduced floor impact noise leading to speech level reduction. Sound fluctuation, as characterised by the metric Noise Climate (NCl: LA10 – LA90) and the psychoacoustic Fluctuation Strength (FS), decreases significantly with increasing number of workstations in OPOs. This suggests lesser auditory distraction in larger offices, which needs further investigation. In terms of historical trends, OPOs have become quieter over the years, especially background noise quantified as LA90, although there are several subtleties. Overall, current findings can inform several OPO design perspectives including policy documents, provide values for laboratory simulations of OPO acoustic environments, help interpret subjective impressions of OPO occupants, etc.
Noise in open-plan offices, and more specifically conversational noise, is a major source of annoyance for employees. The principle of sound masking consists in artificially increasing the background noise in the office, which leads to a decrease in speech intelligibility and therefore a reduction in acoustic annoyance. Nevertheless, the arguments in favour of this technology are based on short-term laboratory studies, whose lack of representativeness limits the application of their conclusions in real open-plan offices. This justifies the present study, which aims to evaluate, in situ and over the long term, the effectiveness of a sound masking system that meets the main scientific and normative recommendations (for example, a masking level below 45 dB(A) and a spectrum with a slope of approximately − 5 dB per octave). Such a sound masking system was installed for several months in an office of a major French banking company. The experiment spanned 26 weeks, 14 of which corresponded to nominal operation of the masking system. The protocol was based on subjective measurements using questionnaires on perceived fatigue, mental workload and perception of the soundscape. The study did not reveal any significant improvement in the assessed psychological factors nor in annoyance caused by office noise. On the contrary, it showed an increase in annoyance caused by noise from office equipment. This highlights the fact that a masking level of 45 dB(A) might already be too high. The results therefore suggest that, in real conditions, a masking system, even if it is used according to specifications that seem to be agreed upon, is not a turnkey solution to the problem of noise in open-plan offices. It is recommended that the installation of these systems be preceded by a holistic analysis of the office: acoustic quality of the room, layout of the workstations and the activities that take place there.
This paper investigates variability in the key ISO 3382-3:2012 metrics, based primarily on the repeatability and reliability of these metrics, using repeated measurements in open-plan offices. Two types of repeated measurements were performed in offices – Type1 (n = 36), where the same path over workstations was measured from opposite ends, and Type2 (n = 7), where two different measurement paths were measured. Analyses performed per metric used (i) the range of observed values, i.e., "∆Type1" , "∆Type2" ; and (ii) the observed values on their actual scales. Results from category (i) analysis: ("∆Type1" ) ̅, and bootstrapped 95% confidence intervals were 1.2 m (0.9,1.5) for distraction distance (rD); 0.8 dB (0.6,1.0) for spatial decay rate of speech (D2,S); 1.2 dB (0.8,1.5) for A-weighted sound pressure level of speech at 4 m (Lp,A,S,4 m); and 1.2 dB (0.7,1.7) for the A-weighted background noise level (Lp,A,B). ("∆Type2" ) ̅ were between twice and thrice the respective values of ("∆Type1" ) ̅. Results from category (ii) analysis: the reliability, based on intra-measurement correlation coefficients for repeated measurements, was fairly high for all metrics, except for Lp,A,S,4 m for Type2 repeats. The repeatability limit/coefficient (r), which is the absolute difference between metric values not expected to be exceeded in 95% of the repeatability conditions, was 2.5 m for rD; 1.7 dB for D2,S; 2.9 dB for Lp,A,S,4 m; and 3.0 dB for Lp,A,B, for Type1 repeats. The r¬ values for Type2 repeats were substantially higher except for D2,S; Lp,A,B not applicable in the current context. Overall, most of the Type1 results seem reasonable considering repeats were conducted in complicated room acoustic environments, while Type2 repeats would benefit from larger sample sizes in future studies. Some recommendations are outlined for the ISO 3382-3 methodology vis-à-vis Type1 and Type2 repeats, including future research directions that go beyond increased sample sizes.
The irrelevant speech effect (ISE) characterizes detriment to cognitive task performance in the presence of irrelevant speech. This paper examines whether the ISE varies due to the number of simultaneously active nearby talkers (for up to two talkers), or the overall sound level, within the context of a simulated open-plan office. Two experiments were conducted within a climate-controlled chamber that was set-up as a medium-sized open-plan office. The cognitive tasks performed by the participants included the digit recall task, and a writing task, within a room acoustic simulation of realistic multi-talker speech from spatially separated talkers. Within Experiment 1 (n = 60), an increase in the number of talkers from none (T0) to one (T1), and from one to two (T2) simultaneous talkers resulted in statistically significant decline in the digit recall task performances, with effect sizes of 24% (i.e., T1 vs. T0), and 12% (i.e., T2 vs. T1), respectively. The pauses between words during the writing task were similar for T0 and T1, but showed a statistically significant increase within T2 vs. T1, with an effect size of 12%. The findings of Experiment 1 are inconsistent with the maximally distracting status attributed to T1 in some studies, but is consistent with findings in other studies. Within Experiment 2 (n = 62), the cognitive performance in T2 remained largely invariant between 45 and 57 dB (A-weighted sound pressure levels), which represents a typical range of levels within open-plan offices. This finding is somewhat consistent with previous studies, where the ISE has been shown to be invariant over large changes to the overall level of more-or-less spatially-static single-talker speech. However, the current findings provide a more ecologically-valid representation of multi-talker level-invariance of the ISE. In general, these findings have relevance for characterizing auditory distraction within complex multi-talker environments; both in laboratory studies and actual open-plan offices.
ISO 3382-3, the international standard for evaluating the acoustics of open-plan offices, includes metrics based on measuring spatial decay, over workstations, of speech sound pressure level, and speech intelligibility. The speech intelligibility metrics, out of which distraction distance (rD) has recently been shown to be most useful, are derived from speech transmission index (STI) calculations. This study examines how the ISO 3382-3 metrics, especially rD, are affected by certain aspects of STI calculation, by using acoustic measurements of 20 offices. Results show that rD values calculated using ISO 3382-3 speech spectrum were significantly different to those calculated using other standard and proposed speech spectra. The choice of standard octave-band transmission index weights, e.g., male/female, used in standard STI calculation as per IEC 60268-16 (2011), did not significantly affect rD values. However, compared to the standard STI calculation, the pre-standard weights from the STI model from 1985 that is used in some important studies cited in ISO 3382-3 yielded much shorter rD values; RASTI yielded an increase in rD of less than 1 m; whereas STIPA (IEC 60268-16: 2011) did not affect rD. The effect of auditory spectral masking in standard STI calculation was negligible overall, but there were cases where the auditory masking reduced rD by up to 0.5 m. The effects of speech spectrum on two other relevant metrics in ISO 3382-3, namely spatial decay rate of speech, and A-weighted sound pressure level of speech at 4m distance, were not significant. Overall, sensitivities of rD to several aspects of STI calculation are highlighted, which should contribute to the interpretation of studies that informed ISO 3382-3 development, support the current implied practice of using male STI weights for genderless speech in the calculation of rD, and provide guidance on potential refinements.
The aim of this paper is to clarify the characteristics of air-conditioner noise and determine the factor that is most influential on the subjective annoyance caused by this noise. The A-weighted equivalent continuous sound pressure level (LAeq) and factors extracted from the autocorrelation function (ACF) were analyzed. Subjective annoyance was evaluated using a paired comparison method. Multiple regression analyses were performed using a linear combination of LAeq, the ACF factors, and their standard deviations (SDs). The results indicated that the noise characteristics caused by each air conditioner and each operating level are determined by LAeq, and by the width of the first decay of the ACF, Wϕ(0), which corresponds to the spectral centroid. The multiple regression analyses indicated that the total subjective annoyance caused by air-conditioner noise can be predicted using the delay time and amplitude of the first maximum peak of the ACF (τ1 and ϕ1) and the SD of ϕ1. Annoyance was found to increase with decreasing τ1 and ϕ1, and with increasing ϕ1 SD, suggesting that noise components with higher pitches, weaker pitch strengths, and larger pitch strength variations cause greater levels of annoyance.
Previous research suggests that, in open-plan offices, noise complaints may be related to the high intelligibility of speech. Distraction distance, which is based on the Speech Transmission Index, can be used to objectively describe the acoustic quality of open-plan offices. However, the relation between distraction distance and perceived noise disturbance has not been established in field studies. The aim of this study was to synthesize evidence from separate studies covering 21 workplaces (N=883 respondents) and a wide range of room acoustic conditions. The data included both questionnaire surveys and room acoustic measurements (ISO 3382-3). Distraction distance, the spatial decay rate of speech, speech level at 4 meters from the speaker and the average background noise level were examined as possible predictors of perceived noise disturbance. The data were analyzed with individual participant data meta-analysis. The results show that distracting background speech largely explains the overall perception of noise. An increase in distraction distance predicts an increase in disturbance by noise whereas the other quantities may not alone be associated with noise disturbance. The results support the role of room acoustic design, i.e., the simultaneous use of absorption, blocking and masking, in the attainment of good working conditions in open-plan offices.
Book on noise effects on man covering audiometry, aural reflex, hearing damage risk, physiological responses, motor performance and speech communication
Ergonomic measurements of noise, lighting and room climate were made in 15 large-space offices in Switzerland. At the same time, 519 employees were given a questionnaire about working in such offices (continuation of work, distractions, disturbances, interpersonal relations, communications, etc.). The correlations among measures indicated the factors that have special influence on the judgments of the large-space office. The results form an objective, usable decision base for the selection and planning of an office building.
Objective and subjective assessments of noise in ten landscaped offices have been carried out. The relative contributions of external noise, air conditioning noise and office activity noise have been determined, and related to subjective response of the occupants. Some design rules and practical remedies for reducing noise are suggested.
A study of the subjective effects of noise is described, in which some 2000 respondents were sampled in 40 offices, representing a wide range of noise conditions. Subsequent analysis of the questionnaire material and the noise recordings indicates that the response to noise may be accounted for by two physical parameters, the average level measured in dBA and the number per minute of impact sounds rising substantially above the background level, which may be correlated with a direct measure of acceptability. The paper puts forward a general model of the response in the form of equally acceptable conditions, and goes on to discuss the problems of setting up practical criteria for noise control.
The aim was to determine how the perceived work environment, especially acoustic environment, and its effects differed in private office rooms and in open-plan offices. The subjects consisted of 31 workers who moved from private office rooms to open-plan offices and who answered the questionnaire before and after the relocation. Private office rooms were occupied only by one person while open-plan offices were occupied by more than 20 persons. Room acoustical descriptors showed a significant reduction in speech privacy after relocation. The noise level averaged over the whole work day did not change but the variability of noise level reduced significantly. Negative effects of acoustic environment increased significantly, including increased distraction, reduced privacy, increased concentration difficulties and increased use of coping strategies. Self-rated loss of work performance because of noise doubled. Cognitively demanding work and phone conversations were most distracted by noise. The benefits that are often associated with open-plan offices did not appear: cooperation became less pleasant and direct and information flow did not change. Nowadays, most office workers, independent of job type, are located in open-plan offices without the individual needs of privacy, concentration and interaction being analysed. This intervention study consisted of professional workers. Their work tasks mainly required individual efforts, and interaction between other workers was not of primary concern, although necessary. The results suggest that the open-plan office is not recommended for professional workers. Similar intervention studies should also be made for other job types.
Noise measurements and a questionnaire survey were carried out in air-conditioned landscaped offices in the present study in an attempt to find out what existing noise index gives the best correlation with the auditory sensation feeling of office workers. Results from statistical analyses show that the Equivalent Sound Pressure LEvel is the best among the 14 commonly used noise indices for this purpose. It is also found that the less commonly used Zwicker's loudness level performs better than the commonly adopted Noise Criterion curves and Noise Rating curves in predicting auditory sensation of office workers in air-conditioned landscaped offices. The performance of the 14 noise indices in predicting auditory comfort are compared.
lme4: linear mixedeffects models using Eigen and S4. R package version 1.0-4. h ttp. Cran r-Project Org/Web/Packages/Lme4/Index Html Accessed
- D Bates
- M Maechler
- B Bolker
- S Walker
Bates D, Maechler M, Bolker B, Walker S. lme4: linear mixedeffects models using Eigen and S4. R
package version 1.0-4. h ttp. Cran r-Project Org/Web/Packages/Lme4/Index Html Accessed 2013;30.