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

Sensory and affective dimensions in loudness perception: Insights from young adults

Traditional psychoacoustic measures often lack accuracy in diagnosing hyperacusis and other sound tolerance disorders, possibly due to their reliance on artificial stimuli and unidimensional scales. The aim of this study was to assess loudness across sensory and affective dimensions using natural sounds, drawing on pain research wherein intensity and unpleasantness are assessed separately. We hypothesized that similar distinctions apply to loudness perception. A total of 102 young adults with normal to mild hearing loss rated 32 sound stimuli (pleasant, unpleasant, neutral, and artificial) at 10 intensities (40 to 100 dBA) on sensory and affective scales. They also completed the Hyperacusis Questionnaire, the Noise Sensitivity Scale, and the Hospital Anxiety and Depression Scale. Mixed linear models indicated both correlations and dissociations between scales that varied according to intensity and valence. Louder stimuli were rated as more unpleasant, but only at high intensities. On the sensory scale, sounds were perceived as louder with increasing intensity; however, at low to moderate intensities, pleasant and neutral sounds were rated as louder, whereas at higher intensities, artificial and unpleasant stimuli were rated as louder. On the affective scale, the perception of unpleasantness also increased with intensity, but less steeply. At high intensities, artificial stimuli were rated similarly to unpleasant stimuli. Noise sensitivity scores predicted louder and more unpleasant ratings, whereas depression scores were associated with softer and less pleasant perceptions. This study highlights the need for multidimensional approaches in audiology and suggests that the integration of sensory and affective scales with natural stimuli may improve the diagnosis and treatment of sound tolerance disorders.

Office soundscape assessment: A model of acoustic environment perception in open-plan officesa)

The soundscape approach has been utilised in recent research for residential environments, but applications to indoor working environments remain limited. This study investigated the suitability of affective quality evaluations of open-plan office acoustics. Perceptual assessments were completed by occupants of eight open-plan office floorplates, using affective dimensions outlined in PD ISO/TS 12913-3:2019 and indoor soundscape studies. Participant demographic, contextual, work-related quality, and psychological well-being data were collected. Workstation noise levels were measured following BS ISO 22955:2021. Principal component analysis identified Pleasantness, Eventfulness, and Emptiness as the main perceptual dimensions, cumulatively explaining 56% of the total variance. Results indicate the suitability of the PD ISO/TS 12913-3:2019 two-dimensional model for open-plan offices. The perceived presence of human sounds negatively correlated with ISO Pleasantness yet positively correlated with ISO Eventfulness. Participant gender and aural diversity mediated ISO Pleasantness. Psychological well-being and work-related quality correlated positively with soundscape pleasantness. No correlations were found between level-based acoustical indicators-equivalent continuous sound level (LAeq), level exceeded 10% (LA10) and 90% (LA90) of the time, level variability (LA10-LA90) and Liveliness-and perceptual scores. A conceptual representation of open-plan office soundscape perception is presented, offering a framework for evaluating and designing workspaces to enhance well-being.

The influence of the reference level on loudness and preference judgements for spectrally manipulated fan sounds

Fan sounds are often quantified using A-weighted sound pressure levels, silently acknowledging their limitations to fully capture the perceived unpleasantness. To overcome this limitation, level adjustments are a way to quantify the subjective preference of spectrally different sounds in listening experiments by adjusting the level of a test sound until it is equally preferred to a fixed reference sound. Since equal loudness contours differ, depending on the overall level, level adjustments might vary for different levels of the reference sound. This study aims to quantify the effects of spectral manipulations on level adjustments for loudness and preference judgements at reference sound pressure levels of either 45, 60, or 75 dB(A). Level adjustments of up to 12 dB were measured to make the stimuli equally preferred to the reference, particularly for sounds with prominent high-frequency components. The loudness and preference judgements were closely linked with each other, but an offset of about 3.5 dB at a reference level of 45 dB(A) indicates that equal loudness is not synonymous with equal preference. A linear regression model to predict level adjustments based on the reference level and an index reflecting the ratio of mid- to high-frequency loudness explains 73% of the variance.

Human-Caused Sound Distractors and their Impact on Operating Room Team Function

BACKGROUND

Patient safety in the Operating Room (OR) depends on unobstructed team communication. Yet the typical OR is loud, containing numerous sounds from surgical machinery overlayed with human-caused sounds. Our objective was to compare machine vs human-caused sounds for their loudness and distraction, and potential impact on team communication.

METHODS

After surveying OR staff about sounds that interfere with job performance and team communication, we recorded 19 machine and 48 human-caused sounds measuring their acoustical intensity. We compared peak measures of machine vs human-caused sound loudness, using Student's t-test. We observed the effect of these sounds on OR staff in 59 live surgeries, rating level of interference with team function. We visually depicted competing sounds through a spectral analysis.

RESULTS

The survey response rate was 62.8%. 93% of respondents indicated that OR noise, especially human-caused sounds such as irrelevant conversations, interfere with team communication, hearing, and focus. OR peak decibel levels ranged from 56.8 dB (surgical packaging) to 105.0 dB (kicked metal stepstool). Human-caused sounds were comparable to machine-caused sounds in terms of mean peak dB levels (77.0 versus 73.8 dB, p = 0.32), yet were rated as more interfering with surgical team function. The spectral analysis illustrated both machine and human-caused sound sources obscuring the surgeon's instructions.

CONCLUSIONS

Avoidable human-caused sounds are a major source of disruption in the OR and interfere with communication and job performance. We recommend surgical team training to minimize these distractions.

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.

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 L_Aeq ), 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.

Where Is the Action in Perception? An Exploratory Study With a Haptic Sensory Substitution Device

Enactive cognitive science (ECS) and ecological psychology (EP) agree that active movement is important for perception, but they remain ambiguous regarding the precise role of agency. EP has focused on the notion of sensorimotor invariants, according to which bodily movements play an instrumental role in perception. ECS has focused on the notion of sensorimotor contingencies, which goes beyond an instrumental role because skillfully regulated movements are claimed to play a constitutive role. We refer to these two hypotheses as instrumental agency and constitutive agency, respectively. Evidence comes from a variety of fields, including neural, behavioral, and phenomenological research, but so far with confounds that prevent an experimental distinction between these hypotheses. Here we advance the debate by proposing a novel double-participant setup that aims to isolate agency as the key variable that distinguishes bodily movement in active and passive conditions of perception. We pilot this setup with a psychological study of width discrimination using the Enactive Torch, a haptic sensory substitution device. There was no evidence favoring the stronger hypothesis of constitutive agency over instrumental agency. However, we caution that during debriefing several participants reported using cognitive strategies that did not rely on spatial perception. We conclude that this approach is a viable direction for future research, but that greater care is required to establish and confirm the desired modality of first-person experience.

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 L_Aeq,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.

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 f_m and depth D_m. A psychoacoustic laboratory experiment was conducted with 40 participants to explore how subjective loudness and annoyance of AM sound depends on f_m (from 0.25 to 16 Hz), D_m (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 L_Aeq, which is typical for environmental noise both indoors and in residential yards. The annoyance penalty increased with increasing f_m and D_m. The penalties varied from 4 to 12 dB, when D_m ranged from 4 to 14 dB and f_m ranged from 1 to 16 Hz. For the lowest f_m= 0.25 Hz, and D_m = 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 f_m and D_m, applied for the periods with AM sound.

Determination of preference-equivalent levels for fan noise and their prediction by indices based on specific loudness patterns

In a previous study by the authors, two indices were identified as appropriate descriptors for perceptual dimensions of fan noise. The index N_low describes the amount of low-frequency loudness relative to the overall loudness. The index N_ratio represents the ratio between the amount of loudness resulting from mid-frequency content and that from high frequencies. The aim of this study is to quantify how variations in these two indices affect subjects' preferences and loudness judgments. In listening experiments, fan noise signals were adjusted separately to equal loudness and equal preference compared to a common reference sound by varying their level in an adaptive procedure. The fan noises used in the listening tests consisted of 11 typical signals from three major groups of fan sounds from the earlier study and 18 signals that were parametrically varied in terms of the two indices. Reductions in A-weighted sound pressure level of up to 15 dB were necessary to make unpleasant fan sounds equally preferred as the fixed reference sound. A regression model based on the index N_ratio explains 81% of the variation in the evaluation data with a root-mean-squared error of 2.53 dB.

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 L_Aeq, 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. R_w + C_50-3150 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.

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 L_Aeq). 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 L_Aeq) 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.

Office noise: Can headphones and masking sound attenuate distraction by background speech?

BACKGROUND

Background speech is one of the most disturbing noise sources at shared workplaces in terms of both annoyance and performance-related disruption. Therefore, it is important to identify techniques that can efficiently protect performance against distraction. It is also important that the techniques are perceived as satisfactory and are subjectively evaluated as effective in their capacity to reduce distraction.

OBJECTIVE

The aim of the current study was to compare three methods of attenuating distraction from background speech: masking a background voice with nature sound through headphones, masking a background voice with other voices through headphones and merely wearing headphones (without masking) as a way to attenuate the background sound. Quiet was deployed as a baseline condition.

METHODS

Thirty students participated in an experiment employing a repeated measures design.

RESULTS

Performance (serial short-term memory) was impaired by background speech (1 voice), but this impairment was attenuated when the speech was masked - and in particular when it was masked by nature sound. Furthermore, perceived workload was lowest in the quiet condition and significantly higher in all other sound conditions. Notably, the headphones tested as a sound-attenuating device (i.e. without masking) did not protect against the effects of background speech on performance and subjective work load.

CONCLUSIONS

Nature sound was the only masking condition that worked as a protector of performance, at least in the context of the serial recall task. However, despite the attenuation of distraction by nature sound, perceived workload was still high - suggesting that it is difficult to find a masker that is both effective and perceived as satisfactory.