Effects Of Sound Pressure Level Research Articles

Experimental study on the removal of submicron droplets by fibrous filter media in a sound field

The acoustic agglomeration technology is proposed as pretreatment to effectively reduce the concentration of particles produced in the industrial process, thus to improve the filtration efficiency of subsequent filter devices. However, the removal of submicron droplets by sound waves has not yet received attention. In this paper, a new method is proposed for high-efficient filtration of submicron droplets based on sound waves. According to the entrainment mechanism of sound waves on the submicron droplets, a sound field is introduced in the filtration system to enhance the collision probability between the droplets and the fibers in filter materials. The effects of sound pressure level (SPL) and sound frequency on the droplet removal were experimentally investigated at different filtration gas velocities. The results show that there is no shift for the upstream particle size distribution, however, the downstream droplet concentration decreases when the sound field is introduced. The effect of the sound field on filtration performance is determined by the vibration amplitude and the vibration period of the droplets. In the SPL range of 130–145 dB, the improvement of the filtration performance is better with the increase of the SPL for a fixed sound frequency. In the frequency range of 500–900 Hz, the optimal filtration performance of the filter material is obtained at 700 Hz. When the filtration gas velocity is between 0.2 and 0.4 m/s, the improvement of the filtration performance gradually weakens as the filtration velocity increases. Furthermore, the reduction of the downstream droplet concentration is more significant for low-efficient filters or those with fewer layers under the same condition in the sound field.

Within- and cross-domain effects of environmental factors on students’ perception in educational buildings

Students in classrooms are exposed to environmental stimuli in the thermal, visual, acoustic and air quality domains, which affect their overall comfort and performance. Therefore, in recent studies, questionnaires are used to collect information about subjective perceptions and investigate links with physical parameters. Most field studies in educational buildings either focus on a single comfort domain, or consider multiple domains but provide inconsistent questions among the 4 domains (i.e., IAQ, thermal, visual and acoustic). Very few studies have investigated cross-domain effects in a consistent manner, considering satisfaction, comfort and perception aspects. To address this research gap, a survey with consistent questions among the 4 comfort domains was designed and used to collect more than 900 subjective responses from students. The analysis of subjective data together with objective measurements allows: (i) correlating the environmental physical parameters and students’ perception in each of the comfort domains; (ii) understanding the students’ preferred environmental conditions; and (iii) understanding cross-domain effects, i.e., the effects between the average conditions and the mean vote expressed for another domain. The results show that air temperature, illuminance and sound pressure level are correlated with the sensation in the respective domains, in contrast to CO2 concentration. Regarding cross-effects, the study confirms interference of CO2 concentration and illuminance on thermal sensation as well as the effect of sound pressure level on visual sensation.

Establishing the acute physiological and sleep disruption characteristics of wind farm versus road traffic noise disturbances in sleep: a randomized controlled trial protocol.

Despite the global expansion of wind farms, effects of wind farm noise (WFN) on sleep remain poorly understood. This protocol details a randomized controlled trial designed to compare the sleep disruption characteristics of WFN versus road traffic noise (RTN). This study was a prospective, seven night within-subjects randomized controlled in-laboratory polysomnography-based trial. Four groups of adults were recruited from; <10 km away from a wind farm, including those with, and another group without, noise-related complaints; an urban RTN exposed group; and a group from a quiet rural area. Following an acclimation night, participants were exposed, in random order, to two separate nights with 20-s or 3-min duration WFN and RTN noise samples reproduced at multiple sound pressure levels during established sleep. Four other nights tested for continuous WFN exposure during wake and/or sleep on sleep outcomes. The primary analyses will assess changes in electroencephalography (EEG) assessed as micro-arousals (EEG shifts to faster frequencies lasting 3-15 s) and awakenings (>15 s events) from sleep by each noise type with acute (20-s) and more sustained (3-min) noise exposures. Secondary analyses will compare dose-response effects of sound pressure level and noise type on EEG K-complex probabilities and quantitative EEG measures, and cardiovascular activation responses. Group effects, self-reported noise sensitivity, and wake versus sleep noise exposure effects will also be examined. This study will help to clarify if wind farm noise has different sleep disruption characteristics compared to road traffic noise.

COMBINED EFFECTS OF PHYSICAL ENVIRONMENT ELEMENTS ON THE PERCEPTION AND COMFORT OF URBAN PUBLIC OPEN SPACE USERS: A UNIVERSITY CAMPUS CASE

Aim: This study examines the effects of urban public spaces, which have physical environmental elements (heat, light, sound, etc.) that vary according to seasons and time of day, on the environmental assessments and quality of life of city residents. Objectively and subjectively investigating the combined effects of such multiple physical environmental elements on people's environmental perception and thermal, auditory, visual and general comfort can make significant contributions to the design and application fields. Method: The study is based on a field study conducted in two open areas with different physical environmental elements on a university campus in Eskişehir. In this context, the difference between objective parameters of various physical environmental elements on the campus (temperature, humidity, sound pressure level, brightness level, etc.) and subjective evaluations obtained from surveys about users' perception and comfort of the physical environment (thermal, auditory, visual and general comfort evaluations). The relationship was examined with statistical analysis. Results: Research results show that horizontal-vertical brightness level, temperature, relative humidity and sky visibility have a significant effect on general comfort. However, the effect and type of effect of sound pressure level and wind speed on general comfort have not been determined. Conclusion: As design input, overhead cover elements and mobile seating units are recommended as improvement strategies that can be developed to increase the general comfort level of campus open spaces. This study can provide valuable guidance in the design and management of urban public spaces.

A Psychological Evaluation Model of a Good Conversation in Knowledge Creative Activities by Multiple People

Japanese companies have been focusing on enhancing the knowledge creative activities of older office workers in recent years. In addition, the way of working in the office has been shifting from traditional divisional routine work to collaborative or creative work, and office spaces are becoming quieter, with an increasing number of extremely quiet spaces (noise level &lt; 40 dB). A sound environment that is too quiet gives workers the impression that it is difficult to converse with others, because they are worried about what people around them may think. The appearance of the knowledge creative society in recent years has led to a desire for changes in the workplace environment to improve the productivity of intellectual activities. To realize a sound environment that encourages knowledge creative activities, study outcomes need to be accumulated. Therefore, to clarify what kind of sound environment would be appropriate for knowledge creative activities by multiple people, we conducted psychoacoustic experiments to examine the effects of sound pressure level (signal-to-noise ratio), type of sound, and reverberation time in conference rooms on the impression of a “good conversation”. In addition, we considered a causal model for the psychological evaluation of a “good conversation” by conducting a multiple regression analysis of psychological evaluations of the experimental participants. The results indicated that a sound environment considered too quiet for multiple people to have discussions about knowledge creative activities lowers the impression of a “good conversation”, whereas high levels of relaxation lead to the impression of a “good conversation”.

Study on psychological evaluation model of a good conversation in knowledge creative activity by multiple people

In recent years, Japanese companies are focusing on enhancing the knowledge creative activities of office workers, and the way of working in the office is shifting from the conventional divisional routine work to collaborative and creative work. On the other hand, office spaces are becoming quiet, and the number of extremely quiet them with noise levels below 40 dB is increasing. Previous studies have reported that a sound environment that is too quiet gives the worker the impression that it is difficult to have a conversation, further accumulation of research results is desired for the construction of a sound environment that enhances knowledge creative activities. Therefore, in this study, focusing on the relationship between sound environment and intellectual productivity, we investigated a sound environment suitable for knowledge creation activities by multiple people. Psychoacoustic experiments were conducted to examine the effects of sound pressure level (signal-to-noise ratio), type of sound and reverberation time of meeting room on the impression of "good conversation". Furthermore, using the psychological evaluation data of the experimental participants, the causal model of psychological evaluation of "good conversation" was examined by multiple regression analysis, and the psychological factors that contribute to the impression of it was clarified.

A Ffowcs Williams-Hawkings numerical aeroacoustic study of varied and fixed-pitch blades of an H-Rotor vertical axis wind turbine

The effects of sound pressure level at two observation positions of a fixed and varied blade pitch angle at Low-Mach unsteady incompressible Reynolds-Average Navier-Stokes flow approach, on an H-rotor Vertical Axis Wind Turbine. The objective of the study is to compare the noise dissipation and output power/energy of the airfoil blades design of the vertical axis wind turbine in residential zones. The Ffowcs Williams-Hawkings (FHWH) techniques were applied to validate the output noise and vortex shedding of the different angles of attacks (AoA). The study postulated that the time history of the calculated sound pressure level at two observers positions: the aeroacoustic, blade vortex interaction noise, flow separations, dynamic stall experience from varied angled of attacks are found to produces less noise and vortex shedding compared to the fixed angle of attack.

Presenting a Signal to Noise Ratio Model Based on the Combined Effect of Sound Pressure Level/frequency, Exposure Time and Oral Potassium: Experimental Study in Rats

Exposure to noise can lead to anatomical, nonauditory, and auditory impacts. The auditory influence of noise exposure is manifested in the form of Noise-induced hearing loss (NIHL). The current study aimed at present a signal to noise ratio model of otoacoustic emission of rats’ ears in the light of the combined effect of sound pressure level, sound frequency, exposure time, and potassium concentration of the used water. In total, 36 adult male rates, whose age varied from 3 to 4 months and had a weight of 200 ± 50 g, were randomly divided into 12 groups, with each group consisting of 3 rats. The rats in both groups (case and control groups) were exposed to SPLs of 85, 95, and 105 dB, emitted from sources that generated white noise. A distortion product otoacoustic emission (DPOAE) machine (4000 I/O manufactured by Homoth of Germany) was utilized to gauge the signal to noise ratio (SNR) of otoacoustic emissions of rats’ ears at various frequencies in an acoustic room. The inclusion criterion was SNR ≥ 6 dB. The collected data were fed into the Statistical Package for Social Sciences (SPSS) version 18, followed by conducting descriptive and inferential data analysis procedures. The results of SNR analysis indicated that over 82% of all data had SNRs that were equal to or greater than 6 dB. These data were considered as acceptable response. Furthermore, SPL and sound frequency had significant associations with SNR (P < 0.0001). Exposure time also significantly correlated with SNR (P = 0.008). However, the potassium concentration of the used water had no significant correlation with SNR (P = 0.97). High sound pressure levels result in lower DPOAE. Furthermore, higher frequency leads to higher SNR. On the contrary, longer exposure time reduces SNR. Finally, the potassium concentration of the used water has no effect on SNR.

Effect of sound pressure level on contralateral inhibition underlying duration-tuned neurons in the mammalian inferior colliculus.

Duration tuning in the mammalian inferior colliculus (IC) is created by the interaction of excitatory and inhibitory synaptic inputs. We used extracellular recordings and paired tone stimulation to measure the strength and time course of the contralateral inhibition underlying duration-tuned neurons (DTNs) in the IC of the awake bat. The onset time of a short, best duration (BD), excitatory probe tone set to +10 dB (re threshold) was varied relative to the onset of a longer-duration, nonexcitatory (NE) suppressor tone whose sound pressure level (SPL) was varied. Spikes evoked by the roving BD tone were suppressed when the stationary NE tone amplitude was at or above the BD tone threshold. When the NE tone was increased from 0 to +10 dB, the inhibitory latency became shorter than the excitatory first-spike latency and the duration of inhibition increased, but no further changes occurred at +20 dB (re BD tone threshold). We used the effective duration of inhibition as a function of the NE tone amplitude to obtain suppression-level functions that were used to estimate the inhibitory half-maximum SPL (ISPL50). We also measured rate-level functions of DTNs with single BD tones varied in SPL and modeled the excitatory half-maximum SPL (ESPL50). There was a correlation between the ESPL50 and ISPL50, and the dynamic range of excitation and inhibition were similar. We conclude that the strength of inhibition changes in proportion to excitation as a function of SPL, and this feature likely contributes to the amplitude tolerance of the responses of DTNs. NEW & NOTEWORTHY Duration-tuned neurons arise from excitatory and inhibitory synaptic inputs offset in time. We measured the strength and time course of inhibition to changes in sound level. The onset of inhibition shortened while its duration lengthened as the stimulus level increased from 0 to +10 dB re threshold; however, no further changes were observed at +20 dB. Excitatory rate-level and inhibitory suppression-level response functions were strongly correlated, suggesting a mechanism for level tolerance in duration tuning.

Acoustic Resistance of an Orifice at High Sound Pressure Levels

The effect of sound pressure level on acoustic resistance of an orifice in a baffle is investigated based on the measurements in an impedance tube by the two-microphone method. Dependences of the resistance of an orifice on the diameter of the latter are obtained for the case of nonlinear mode of operation. It is shown that, in this case, the resistance of the orifice depends on its diameter. The dependence of the nonlinear resistance on particle velocity in the orifice is approximated by a linear function.

The Effect of Occupational Noise Exposure on Serum Cortisol Concentration of Night-shift Industrial Workers: A Field Study.

BackgroundIn both developed and developing countries, noise is regarded as the most common occupational hazard in various industries. The present study aimed to examine the effect of sound pressure level (SPL) on serum cortisol concentration in three different times during the night shift.MethodsThis case–control study was conducted among 75 workers of an industrial and mining firm in 2017. The participants were assigned to one of the three groups (one control and two case groups), with an equal number of workers (25 participants) in each group. Following the ISO 9612 standard, dosimetry was adopted to evaluate equivalent SPL using a TES-1345 dosimeter. The influence of SPL on serum cortisol concentration was measured during the night shift. The serum cortisol concentration was measured using a radioimmunoassay (RIA) test in the laboratory. Repeated measure analysis of variance and linear mixed models were used with α = 0.05.ResultsThe results indicated a downward trend in the serum cortisol concentration of the three groups during the night shift. Both SPL and exposure time significantly affected cortisol concentration (p < 0.0001, p < 0.0001). Conversely, age and body mass index had no significant influence on cortisol concentration (p = 0.360, p = 0.62).ConclusionBased on the obtained results, increasing SPL will lead to enhancement of serum cortisol concentration. Given that cortisol concentration varies while workers are exposed to different SPLs, this hormone can be used as a biomarker to study the effect of noise-induced stress.

Inertial Attached Length of an Orifice at High Sound Pressure Levels

Effect of sound pressure level on acoustic impedance of an orifice in a baffle is investigated based on the measurements performed in an impedance tube by the two-microphone method. Dependences of imaginary and real parts of impedance on the orifice diameter are obtained in nonlinear conditions. Special attention is paid to the attached length (the end correction) of the orifice. Dependence of the attached length of an orifice on the oscillating velocity in it is approximated by analytic functions.

Effects of sound pressure level and visual perceptual load on the auditory mismatch negativity

Auditory change detection has been studied extensively with mismatch negativity (MMN), an event-related potential. Because it is unresolved if the duration MMN depends on sound pressure level (SPL), we studied effects of different SPLs (56, 66, and 76dB) on the duration MMN. Further, previous research suggests that the MMN is reduced by a concurrent visual task. Because a recent behavioral study found that high visual perceptual load strongly reduced detection sensitivity to irrelevant sounds, we studied if the duration MMN is reduced by load, and if this reduction is stronger at low SPLs. Although a duration MMN was observed for all SPLs, the MMN was apparently not moderated strongly by SPL, perceptual load, or their interaction, because all 95% CIs overlapped zero. In a contrast analysis of the MMN (across loads) between the 56-dB and 76-dB groups, evidence (BF=0.31) favored the null hypothesis that duration MMN is unaffected by a 20-dB increase in SPL. Similarly, evidence (BF=0.19) favored the null hypothesis that effects of perceptual load on the duration MMN do not change with a 20-dB increase in SPL. However, evidence (BF=3.12) favored the alternative hypothesis that the effect of perceptual load in the present study resembled the overall effect in a recent meta-analysis. When the present findings were combined with the meta-analysis, the effect of load (low minus high) was −0.43μV, 95% CI [−0.64, −0.22] suggesting that the duration MMN decreases with load. These findings provide support for a sensitive monitoring system of the auditory environment.

A Model to Determine the Level of Serum Aldosterone in the Workers Attributed to the Combined Effects of Sound Pressure Level, Exposure Time and Serum Potassium Level: A Field-Based Study

Background: Occupational exposure to excessive noise is one of the biggest work-related challenges in the world. This phenomenon causes the release of stress-related hormones, which in turn, negatively affects cardiovascular risk factors. Objectives: The current study study aimed to determine the level of workers’ serum aldosterone in light of the combined effect of sound pressure level, exposure time and serum potassium level. Methods: This cross-sectional, descriptive, analytical study was conducted on 45 workers of Gol-Gohar Mining and Industrial Company in the fall of 2014. The subjects were divided into three groups (one control and two case groups), each including 15 workers. Participants in the control group were selected from workers with administrative jobs (exposure to the background noise). On the other hand, participants in the case groups were selected from the concentrator and pelletizing factories exposed to excessive noise. Serum aldosterone and potassium levels of participants were assessed at three different time intervals: at the beginning of the shift and before exposure to noise (7:30 - 8:00 AM), during exposure to noise (10:00 - 10:30 AM), and during continuous exposure (1:30 - 2:00 PM). The obtained data were transferred into SPSS ver. 18. Repeated measures analysis of variance (ANOVA) was used to develop the statistical model of workers’ aldosterone level in light of the combined effect of sound pressure level, exposure time, and serum potassium level. Results: The results of the final statistical model to determine the level of serum aldosterone based on the combined effect of sound pressure level, exposure time and serum potassium level indicated that the sound pressure level had a significant influence on the human’s serum aldosterone level (P = 0.04). In addition, the effects of exposure time and serum potassium on aldosterone level were statistically significant with P-values of 0.008 and 0.001, respectively. Conclusions: The obtained model in the study revealed that the results of predictive models to determine aldosterone level were very similar to real values; therefore, the obtained values of this model were largely in line with the ones obtained from the field.

A Model to Determine the Level of Serum Aldosterone in the Workers Attributed to the Combined Effects of Sound Pressure Level, Exposure Time and Serum Potassium Level: A Field-Based Study

Background: Occupational exposure to excessive noise is one of the biggest work-related challenges in the world. This phenomenon causes the release of stress-related hormones, which in turn, negatively affects cardiovascular risk factors. Objectives: The current study study aimed to determine the level of workers’ serum aldosterone in light of the combined effect of sound pressure level, exposure time and serum potassium level. Methods: This cross-sectional, descriptive, analytical study was conducted on 45 workers of Gol-Gohar Mining and Industrial Company in the fall of 2014. The subjects were divided into three groups (one control and two case groups), each including 15 workers. Participants in the control group were selected from workers with administrative jobs (exposure to the background noise). On the other hand, participants in the case groups were selected from the concentrator and pelletizing factories exposed to excessive noise. Serum aldosterone and potassium levels of participants were assessed at three different time intervals: at the beginning of the shift and before exposure to noise (7:30 - 8:00 AM), during exposure to noise (10:00 - 10:30 AM), and during continuous exposure (1:30 - 2:00 PM). The obtained data were transferred into SPSS ver. 18. Repeated measures analysis of variance (ANOVA) was used to develop the statistical model of workers’ aldosterone level in light of the combined effect of sound pressure level, exposure time, and serum potassium level. Results: The results of the final statistical model to determine the level of serum aldosterone based on the combined effect of sound pressure level, exposure time and serum potassium level indicated that the sound pressure level had a significant influence on the human’s serum aldosterone level (P = 0.04). In addition, the effects of exposure time and serum potassium on aldosterone level were statistically significant with P-values of 0.008 and 0.001, respectively. Conclusions: The obtained model in the study revealed that the results of predictive models to determine aldosterone level were very similar to real values; therefore, the obtained values of this model were largely in line with the ones obtained from the field.

Research on the sound absorption characteristics of porous metal materials at high sound pressure levels

Porous metal materials are widely used in noise control with high sound pressure applications such as aircraft engine liners and combustion chambers for rocket engines due to their excellent performance of sound absorption characteristics and distinguished advantages in heat resistance, lightness, and stiffness. Understanding the effect of sound pressure on the acoustic properties of these materials is crucial when attempting to predict silencer performance. In this article, we experimentally investigate the sound absorption characteristics of porous metal materials at high sound pressure level. The effects of material parameters on the sound absorption characteristics of porous metal materials under high sound pressure level are further explored experimentally. Measurements are carried out by using a standard impedance tube that has been modified to accommodate sound pressure level of up to 150 dB. The experimental results show that with the increase in sound pressure level, the effect of sound pressure level on the sound absorption characteristics yields different variation regularities in different frequencies. The sound absorption performance of porous metal materials increases with the increase in sound pressure level in low frequency, which is reasonably consistent with the theoretical results. Under high sound pressure level, the sound absorption characteristics are significantly dependent upon the material parameters such as the metal fiber diameter, the material porosity, and the material thickness. It could provide a reliable experimental validation for the applications of porous metal materials in the area of vibration and noise control at high sound pressure levels.

High fidelity tonotopic mapping using swept source functional magnetic resonance imaging

Tonotopy, the topographic encoding of sound frequency, is the fundamental property of the auditory system. Invasive techniques lack the spatial coverage or frequency resolution to rigorously investigate tonotopy. Conventional auditory fMRI is corrupted by significant image distortion, sporadic acoustic noise and inadequate frequency resolution. We developed an efficient and high fidelity auditory fMRI method that integrates continuous frequency sweeping stimulus, distortion free MRI sequence with stable scanner noise and Fourier analysis. We demonstrated this swept source imaging (SSI) in the rat inferior colliculus and obtained tonotopic maps with ~2 kHz resolution and 40 kHz bandwidth. The results were vastly superior to those obtained by conventional fMRI mapping approach and in excellent agreement with invasive findings. We applied SSI to examine tonotopic injury following developmental noise exposure and observed that the tonotopic organization was significantly disrupted. With SSI, we also observed the subtle effects of sound pressure level on tonotopic maps, reflecting the complex neuronal responses associated with asymmetric tuning curves. This in vivo and noninvasive technique will greatly facilitate future investigation of tonotopic plasticity and disorders and auditory information processing. SSI can also be adapted to study topographic organization in other sensory systems such as retinotopy and somatotopy.

Effects of Sound on Postural Stability during Quiet Standing

Loss of postural stability can increase the likelihood of slips and falls in workplaces. The present study intended to extend understanding of the effects of frequency and pressure level of sound on postural stability during standing. Eleven male subjects participated. Standing on a force platform, the subjects' center of pressures were measured under different combinations of pressure level and frequency of the sound. Variables such as the position variability of COP and the length of postural sway path in anterior-posterior (AP) and medio-lateral (ML) direction were evaluated. Subjective ratings of perceived disturbance at each experimental condition were also obtained using a 7-point rating scale. Results showed that the length of sway path and the position variability of COP increased as the frequency of sound increased in posterior-anterior axis. The effect of sound pressure level, however, was not significant on both the postural sway length and the position variability of COP. These results suggested substantial disturbance of standing balance system among subjects exposed to high frequency noise. The results implied that physical workers should be alerted that their abilities of postural balance could be degraded significantly as disturbance caused by a sound existed.

The Influence of an Acoustic Field on the Bed Expansion of Fine Particles

Fine particles are difficult to fluidize due to strong interparticle attraction. An attempt has been made to study the bed expansion of silica gel ( d p = 25 μm) powder in presence of an acoustic field. A 135 mm diameter fluidized bed activated by an acoustic field with sound intensity up to 145 dB and frequency from 90 Hz to 170 Hz was studied. The effects of sound pressure level, sound frequency and particle loading on the bed expansion were investigated. Experimental results showed that, bed expansion was good in presence of acoustic field of particular frequency. In addition, it was observed that in presence of acoustic field the bed collapses slowly.

Effects of acoustic vibration on nano and sub-micron powders fluidization

Fluidization of nano and sub-micron powders with and without acoustic vibration was investigated. The effects of sound pressure level and frequency were studied. Loudspeakers located under the distributor plate were used as the sound source to disintegrate larger agglomerates concentrated at the bottom of the bed. Nanoparticles showed fluid-like behavior similar to Geldart's A group and application of sound vibration improved their fluidization quality. Submicron particles were hard to fluidize and their fluidization quality was partially improved by sound excitation. Bed compaction, caused by rearranging of the agglomerates, was observed for submicron particles at low gas velocities while the bed was fixed. Nanoparticles did not experience any bed compaction. Sound vibration led to a decrease in minimum fluidization velocity and an increase in bed pressure drop and bed expansion for both types of particles. The fluidization quality of both particles increased at low frequencies, while the reverse was observed at higher frequencies. Fluidization of these particles was improved by increasing sound pressure level. There was a critical sound pressure level of 110 dB, below which the effect of sound vibration was insignificant. A novel technique was employed to find the apparent minimum fluidization velocity from pressure drop signals.