The effects of irrelevant speech on physiological stress, cognitive performance, and subjective experience - Focus on heart rate variability.

Irrelevant speech impairs cognitive performance, especially in tasks requiring verbal short-term memory. Working on these tasks during irrelevant speech can also cause a physiological stress reaction. The aim of this study was to examine heart rate variability (HRV) as a non-invasive and easy-to-use stress measure in an irrelevant speech paradigm. Thirty participants performed cognitive tasks (n-back and serial recall) during two sound conditions: irrelevant speech (50 dB) and quiet (33 dB steady-state noise). The influence of conditions as well as presentation orders of conditions were examined on performance, subjective experience, and physiological stress. Working during irrelevant speech compared to working during quiet reduced performance, namely accuracy, in the serial recall task. It was more annoying, heightened the perceived workload, and lowered acoustic satisfaction. It was related to higher physiological stress by causing faster heart rate and changes in HRV frequency-domain analysis (LF, HF and LF/HF). The order of conditions showed some additional effects. When speech was the first condition, 3-back performance was less accurate, and serial recall response times were longer, heart rate was faster, and successive heart beats had less variability (lower RMSSD) during speech than during quiet. When quiet was the first condition, heart rate was faster and reaction times in 3-back were slower during quiet than during speech. The negative effect of irrelevant speech was clear in experience, performance, and physiological stress. The study shows that HRV can be used as a physiological stress measure in irrelevant speech studies.

Sound insulation dataset of 30 wooden and 8 concrete floors tested in laboratory conditions.

In a Finnish-Swedish consortium project, a large amount of sound insulation tests was conducted for several intermediate floors in laboratory conditions to serve various scientific research questions. The dataset contains 30 wooden and 8 concrete constructions which are commonly used between apartments in multistorey buildings. Impact sound insulation was determined according to ISO 10140-3 standard using both tapping machine and rubber ball as standard sound sources. Airborne sound insulation was determined according to the ISO 10140-2 standard. The data are special since they have a broad frequency range: 20-5000 Hz. Data are reported in 1/3-octave frequency bands and the single-number values of ISO 717-1 and ISO 717-2 are also reported. Detailed construction drawings are available for all reported constructions. The data are highly valuable for research, education, and development purposes since all data were obtained in the same laboratory (Turku University of Applied Sciences, Turku, Finland), and all the constructions were built by the same installation team.

Speech is special: The stress effects of speech, noise, and silence during tasks requiring concentration.

Effects of noise on people depend on sound level but also on other sound properties. A systematic comparison of the stress effects of speech and noise with the same frequency content is missing. This study compared stress reactions under sound conditions speech (sound level 65 dB LAeq ), noise (65 dB), and silence (35 dB), all having similar relative frequency contents. Fifty-nine participants were exposed to one out of three sound conditions on average for 48 minutes while performing tasks requiring concentration. Acute physiological stress was estimated by measuring stress hormone concentrations in plasma (cortisol and noradrenaline), heart rate variability (HRV), and blood pressure. Psychological stress measures were subjective noise annoyance, workload, and fatigue. Compared to silence and noise, working during speech was more annoying, loading, but less tiring, and led to elevated HRV LF/HF ratio with time. Speech also raised cortisol levels compared with silence. Although noise was more annoying, and raised cortisol levels compared with silence, working during speech was more loading and caused more physiological stress than other sound conditions. Special care should be paid to noise control in workplaces requiring concentration because already exposure to moderate sound level sounds caused clear physiological effects on people.

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.

The relation between the intelligibility of irrelevant speech and cognitive performance-A revised model based on laboratory studies.

Irrelevant background speech causes dissatisfaction and impairs cognitive performance in open-plan offices. The model of Hongisto (2005, Indoor Air, 15, 458-468) predicts the relation between cognitive performance and the intelligibility of speech described with an objectively measured quantity, the Speech Transmission Index (STI). The model has impacted research in psychology and room acoustics as well as the acoustic design guidelines of offices. However, the model was based on scarce empirical data. The aim of this study was to revise the model based on a systematic literature review, focusing on laboratory experiments manipulating the STI of speech by wide-band steady-state noise. Fourteen studies reporting altogether 34 tests of the STI-performance relation were included. According to Model 1 that includes all tests, performance begins to decrease approximately above STI = 0.21 while the maximum decrease is reached at STI = 0.44. Verbal short-term memory tasks were most strongly and very consistently affected by the STI of speech. The model for these tasks showed a deterioration in performance between STI 0.12 and 0.51. Some evidence of an STI-performance relation was found in verbal working memory tasks and limited evidence in complex verbal tasks. Further research is warranted, particularly concerning task-specific effects.

Effect of the frequency spectrum of road traffic noise on sleep: A polysomnographic study.

Spectrum of sound affects noise annoyance. Spectral differences of road traffic noise (RTN) transmitted indoors are usual because of spectrally different sound insulation of facades. The purpose was to compare the effect of RTN spectrum on sleep. Twenty-one volunteers slept three nights in a sleep laboratory in three sound conditions: low-frequency (LF) RTN, high-frequency (HF) RTN, and quiet (control). The A-weighted equivalent levels were 37, 37, and 17 dB LAeq,8h, respectively. The nocturnal time profiles of LF and HF were equal. Sleep was measured with polysomnography and questionnaires. HF and LF did not differ from each other in respect to their effects on both objective and subjective sleep quality. The duration of deep sleep was shorter, satisfaction with sleep lower, and subjective sleep latency higher in HF and LF than in quiet. Contrary to subjective ratings given right after the slept night, HF was rated as the most disturbing condition for sleep after the whole experiment (retrospective rating). The finding suggests the sound insulation spectrum of the facade construction might play a role regarding the effects of RTN. More research is needed about the effects of spectrum on sleep because the field is very little investigated.

Optimized reference spectrum for rating the impact sound insulation of concrete floors.

It has been long recognized that the single-number quantities presented in the standard ISO 717-2 [(2013) International Organization for Standardization] do not correlate especially well with the subjective judgment of living impact sound sources directed to the floors. The aim of this study was to find single-number quantities which are well associated with the subjective annoyance caused by different impact sounds. Experimental data of laboratory measurements of impact sound insulation of floors and a psychoacoustic experiment was used [Kylliäinen et al. (2017). Acta Acust. Acust. 103, 236-251]. The five studied impact sound types were walking with hard shoes, socks, and soft shoes, super ball bouncing, and chair moving. A fundamental requirement was that the single-number quantities can be expressed as the sum of L'n,w or L'n T, w and a spectrum adaptation term. Reference spectra were derived by the means of a mathematical optimization method. Reference spectra for each sound type were defined separately. An optimized reference spectrum based on all five sound types explained the annoyance of these sound types reasonably well (r2 = 0.93) and better than any of the standardized single number quantities (e.g., r2 = 0.86 for L'n,w + CI,50-2500).

Annoyance penalty of periodically amplitude-modulated wide-band sound.

Amplitude modulation exists in many environmental noise types. A penalty has been suggested for legal noise assessment to such sounds, but the scientific evidence is limited. The purpose of this research was to determine the annoyance penalty of amplitude modulated (AM) sound as a function of the modulation frequency fm and depth Dm. A psychoacoustic laboratory experiment was conducted with 40 participants to explore how subjective loudness and annoyance of AM sound depends on fm (from 0.25 to 16 Hz), Dm (from 1 to 14 dB), and overall spectrum (two alternatives). The sounds consisted of both AM sounds and reference sounds without amplitude modulation. The AM sounds were played at 35 dB LAeq, which is typical for environmental noise both indoors and in residential yards. The annoyance penalty increased with increasing fm and Dm. The penalties varied from 4 to 12 dB, when Dm ranged from 4 to 14 dB and fm ranged from 1 to 16 Hz. For the lowest fm= 0.25 Hz, and Dm = 1 dB, no penalty could be suggested. The results suggest a potential need for a penalty for low-level AM sounds for certain ranges of fm and Dm, applied for the periods with AM sound.

Subjective and objective rating of the sound insulation of residential building façades against road traffic noise.

Sound insulation in a building façade plays a key role in the control of road-traffic noise. Façade performance can be described using various internationally standardized single-number quantities (SNQs) with different frequency weightings. The purpose of this study was to evaluate how 25 different SNQs explain the subjective ratings of spectrally different road-traffic sounds transmitted through a façade. Forty-three participants took part in a psychoacoustic laboratory experiment. The task was to evaluate five spectrally different road-traffic sound types transmitted through 12 simulated façade constructions. The participants rated both the loudness and the annoyance of 60 sounds. The playback levels were between 12 and 46 dB LAeq, covering the essential range of road-traffic noise usually measured inside residential dwellings. Linear correlations were determined between the SNQ values of the façades and the subjective ratings. Rw + C50-3150 explained the subjective ratings best when the five sound types were equally considered. It was also the most suitable SNQ for the standard road-traffic spectrum of ISO 717-1. The results of this study can be useful in the development of future standards.

Indoor noise annoyance due to 3-5 megawatt wind turbines-An exposure-response relationship.

The existing exposure-response relationships describing the association between wind turbine sound level and noise annoyance concern turbine sizes of 0.15-3.0 MW. The main purpose of this study was to determine a relationship concerning turbines with nominal power of 3-5 MW. A cross-sectional survey was conducted around three wind power areas in Finland. The survey involved all households within a 2 km distance from the nearest turbine. Altogether, 429 households out of 753 participated. The households were exposed to wind turbine noise having sound levels within 26.7-44.2 dB LAeq. Standard prediction methods were applied to determine the sound level, LAeq, in each participant's yard. The measured sound level agreed well with the predicted sound level. The exposure-response relationship was derived between LAeq outdoors and the indoor noise annoyance. The relationship was in rather good agreement with two previous studies involving much smaller turbines (0.15-1.5 MW) under 40 dB LAeq. The Community Tolerance Level (CTL), CTL20 = 50 dB, was 3 dB lower than for two previous studies. Above 40 dB, a small number of participants prevented a reliable comparison to previous studies.

Perception of Water-Based Masking Sounds-Long-Term Experiment in an Open-Plan Office.

A certain level of masking sound is necessary to control the disturbance caused by speech sounds in open-plan offices. The sound is usually provided with evenly distributed loudspeakers. Pseudo-random noise is often used as a source of artificial sound masking (PRMS). A recent laboratory experiment suggested that water-based masking sound (WBMS) could be more favorable than PRMS. The purpose of our study was to determine how the employees perceived different WBMSs compared to PRMS. The experiment was conducted in an open-plan office of 77 employees who had been accustomed to work under PRMS (44 dB LAeq). The experiment consisted of five masking conditions: the original PRMS, four different WBMSs and return to the original PRMS. The exposure time of each condition was 3 weeks. The noise level was nearly equal between the conditions (43-45 dB LAeq) but the spectra and the nature of the sounds were very different. A questionnaire was completed at the end of each condition. Acoustic satisfaction was worse during the WBMSs than during the PRMS. The disturbance caused by three out of four WBMSs was larger than that of PRMS. Several attributes describing the sound quality itself were in favor of PRMS. Colleagues' speech sounds disturbed more during WBMSs. None of the WBMSs produced better subjective ratings than PRMS. Although the first WBMS was equal with the PRMS for several variables, the overall results cannot be seen to support the use of WBMSs in office workplaces. Because the experiment suffered from some methodological weaknesses, conclusions about the adequacy of WBMSs cannot yet be drawn.

Distraction distance and perceived disturbance by noise-An analysis of 21 open-plan offices.

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 (2012) (International Organization for Standardization, Geneva, Switzerland]. Distraction distance, the spatial decay rate of speech, speech level at 4 m 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.

Optimized single-number quantity for rating the airborne sound insulation of constructions: Living sounds.

ISO 717-1 [(1996). International Organization for Standardization, Geneva, Switzerland] and ASTM 413 [(2010). American Society for Testing and Materials International] define various single-number quantities (SNQs) that are commonly used to rate objectively airborne sound insulation of constructions. Recent psychoacoustic evidence suggests that none of them is appropriate for a wide range of living sound stimuli. The purpose of the study was to develop an alternative compromising SNQ for the frequency range 50-5000 Hz that explains well the annoyance caused by various airborne living sounds transmitted from the neighboring dwelling. Optimal reference spectra for different living sounds were found by mathematical optimization. Experimental data from a psychoacoustic laboratory study [Hongisto, Oliva, and Keränen (2014). Acta Acust. Acust. 100, 848-863] were utilized. The subjects (n = 59) had evaluated the disturbance of living sounds that were electrically filtered to mimic transmission through commonly used wall structures. To find a high-performing reference spectrum for living sounds in general, the optimized reference spectra were averaged over all sound types. The resulting SNQ was called Rw + Copt. The related reference spectrum deviates significantly from the reference spectrum for living activities, C50-5000, below 315 Hz. The suggested SNQ correlates better with the subjective disturbance caused by living sounds than any of the present standardized SNQs of ISO 717-1 or ASTM 413.

Subjective and objective rating of spectrally different pseudorandom noises--implications for speech masking design.

Artificial sound masking is increasingly used in open-plan offices to improve speech privacy and to reduce distraction caused by speech sounds. Most of the masking sounds are based on pseudorandom continuous noise filtered to a specific spectrum that should be optimized in respect with speech masking efficiency and comfort. The aim of this study was to increase basic understanding regarding the comfort. The second aim was to determine how well objective rating methods (15 different noise indices) predict the subjective ratings. Twenty-three subjects rated the loudness, disturbance, pleasantness, and six other subjective measures of 11 spectrally different noises in laboratory conditions. Speech was not present during the experiment. All sounds were presented at 42 dB LAeq within 50-10,000 Hz. Unexpectedly, the subjects were most satisfied with sounds having emphasis on low frequencies. A sound having a slope of -7 dB per octave increment resulted in the highest satisfaction. Changes in subjective ratings were reasonably well predicted by five noise indices, while many well-known noise indices frequently used in building design underperformed in this task. The results are expected to benefit in the design of masking sounds and other appliances.

Experimental comparison between speech transmission index, rapid speech transmission index, and speech intelligibility index.

During the acoustical design of, e.g., auditoria or open-plan offices, it is important to know how speech can be perceived in various parts of the room. Different objective methods have been developed to measure and predict speech intelligibility, and these have been extensively used in various spaces. In this study, two such methods were compared, the speech transmission index (STI) and the speech intelligibility index (SII). Also the simplification of the STI, the room acoustics speech transmission index (RASTI), was considered. These quantities are all based on determining an apparent speech-to-noise ratio on selected frequency bands and summing them using a specific weighting. For comparison, some data were needed on the possible differences of these methods resulting from the calculation scheme and also measuring equipment. Their prediction accuracy was also of interest. Measurements were made in a laboratory having adjustable noise level and absorption, and in a real auditorium. It was found that the measurement equipment, especially the selection of the loudspeaker, can greatly affect the accuracy of the results. The prediction accuracy of the RASTI was found acceptable, if the input values for the prediction are accurately known, even though the studied space was not ideally diffuse.