High Sound Pressure Levels Research Articles

Generation of broadband airborne ultrasound using an Harmonic Acoustic Pneumatic Source

This paper presents a new type of airborne transducer for generating broadband ultrasound with a high Sound Pressure Level (SPL). The concept is based on the Harmonic Acoustic Pneumatic Source (HAPS) that uses pressurized air in conjunction with a flow chopper made up of a rotating cage with slots connected to a specific exhaust. The fundamental frequency depends on the number of slots and the rotation speed of the cage. An analytical model of the HAPS coupled with a numerical model of the exhaust is used to predict the radiated acoustic pressure and to estimate the influence of dimensional parameters on pressure level generated by the source. Experiments are conducted with two cages: one with one slot in order to generate pulses periodically and one with 122 slots to generate periodic sound. The level of sound pressure is measured as a function of distance (0.004 to 0.5 m), the cage rotation (up to 11 krpm) and directivity (0 to 90°). For the fundamental frequency at 22 kHz, the maximum SPL of 150 dB (632 Pa rms) is /measured at 0.004 m, and decreases to 122 dB (35 Pa rms) at 0.5 m. At 0.5 m, the second and third harmonics can generate a SPL equal or greater than 115 dB above 22 kHz and up to 66 kHz. Discrepancies between the experiments results and numerical model are observed in terms of SPL, directivity and in-axis pressure.

Non-auditory effects of noise at work: an overview and perspective

It is widely known that noise at high sound pressure levels may have adverse effects on the auditory system, which can end up in noise-induced hearing loss. In addition to these auditory effects, non-auditory effects of noise, which can already appear at moderate levels, should be thoroughly considered in an occupational context in order to ensure safety and health at work. An overview of non-auditory effects will be given, along the questions: Which effects are typically summarised under the term "non-auditory effects"? What approaches are frequently used to uncover these effects? With regard to cognitive performance: Which other factors can influence the effects of noise? Why is it often challenging to verify detrimental effects caused by noise, although most people feel disturbed? Along the legal regulations in Germany, it will be explained what the term "rating level" means and for which categories of professional activities what rating levels must not be exceeded in order to avoid or minimise non-auditory effects. Finally, by means of results from own studies carried out at BAuA, it will be shown that also sounds at moderate levels can lead to detrimental effects, and what issues may occur when trying to reveal effects on cognitive performance.

High sound pressure level sound absorption in acoustic resonant metamaterials: adapting a mass-spring model for nonlinear effects

In aerospace, conventional materials as micro-perforated panels backed by cavities are used to absorb sound at high sound pressure levels. These solutions are not optimal at low frequencies compared to resonant acoustic metamaterials, which present an acoustic absorption peak with a wavelength-to-thickness ratio greater than conventional materials, i.e., a ratio>>5. Acoustic resonant metamaterials are mainly studied at low sound pressure levels (<100dB). However, they are sensitive to increasing the amplitude of acoustic excitation. The studied metamaterial is composed of a compact array of thin single-perforation panels spaced by thin cylindrical air cavities. In a previous study, a mass-spring model was developed for low sound pressure levels. The perforations are modeled by equivalent masses, whereas cavities by equivalent springs. In the perforations, high values of the acoustic velocity lead to an increase in the acoustic resistance of the material. This effect is considered by the Forchheimer parameter in the mass-spring model. To determine this parameter and to study how it is impacted by the metamaterial geometry, the computational fluid dynamic method is used. The mass-spring model is adapted with a nonlinear term. The adapted model agrees well with simulations by finite element method at sound pressure levels up to 140dB.

Systematic review of environmental noise in neonatal intensive care units.

To systematically review the literature on noise exposure within the neonatal intensive care unit/special care nursery settings, specifically to describe: noise characteristics, sources of noise and ways of measuring noise. Systematic searches were conducted through databases Medline, Embase and PubMed. Studies were included if they met the inclusion criteria (1) reported noise characteristics; (2) reported noise exposure measurements; (3) in the neonatal intensive care unit/ special care nursery settings. Methods and key findings were extracted from included studies. Quality analysis was done using a modified version of the Newcastle-Ottawa Scale. We identified 1651 studies, screened 871, reviewed 112 and included 47. All reported NICU average equivalent sound levels were consistently louder than recommended guidelines (45 dB). The most consistent association with higher sound pressure levels were noise sources grouped under people congregation. Half of the studies did not use measuring devices adhering to international sound level meter (SLM) standards. All NICUs exceeded recommended accumulative sound levels. People were the most consistent source of noise. Sound pressure levels need to be consistently measured with devices adhering to international SLM standards in future studies.

Acoustic comfort in primary- and nursery-school canteens: From measurements to recommendations

Canteens usually have critical acoustic conditions resulting from the need to maximize the number of occupants while minimizing volume. Thus, in the absence of specific sound absorbing treatments, very high sound pressure levels are usually observed resulting in significant impairment of communication (with increased vocal effort of speakers and reduced speech intelligibility), and dangerously high exposure levels for workers. The present paper reports acoustic measurements carried out in a nursery school canteen having a volume of 212 m3 and seating about 50 children, and two primary school canteens having volumes of 656 m3 (seating 150 children) and 367 m3 (seating 107 children). Reverberation time was measured in each room as well as sound pressure levels during peak occupation (averaged over 15-minute intervals), resulting in A-weighted sound pressure levels spanning between 81 dB (in the nursery school) and 90 dB in the primary schools. Starting from the observed values, considerations about the group-size of the occupants as a function of age were made, and recommendations were finally given to guide the acoustic correction of similar spaces.

Traffic sounds in office spaces: PLS-SEM study on audio-visual perception with open or closed windows and biophilic design

Herein, we investigated the audio–visual perception of indoor greenery and intruding traffic sounds through open or closed windows in a shared office context that accommodates two people. A set of 32 audio–visual stimuli was used, featuring combinations of greenery dosages (0 %, 7 %, 10 % and 13 %) and traffic sound levels (50 dBA, 55 dBA, 60 dBA and 65 dBA), for both open and closed windows. These stimuli were presented to 42 participants in an indoor office environment using two-dimensional screens and over-ear headphones. We employed a partial least squares structural equation model to integrate greenery dosages, traffic sound levels and perceptual attributes such as pleasantness, eventfulness, appropriateness, preference and visual aesthetics. The findings demonstrate the impact of traffic sound levels on visual perception, highlighting a bidirectional interaction between auditory and visual perceptions. Indoor greenery indirectly enhances the pleasantness of the auditory environment, supporting the implementation of biophilic design in office spaces that are visually appealing and acoustically pleasant. Furthermore, the study contributes to discussions on adaptive acoustic comfort in naturally ventilated spaces, providing evidence of how visual perception impacts the acoustic environment. While the research results highlight the positive impact of open windows on the appropriateness ratings of traffic sounds, it is important to consider the limitation of assessing outdoor-recorded traffic sounds at high sound pressure levels (50–65 dBA) without the filtering effect of the facade. This limitation reduces the realism and ecological validity of the experiment, which should be considered when interpreting these results.

Ultrasonic Haptic Devices: Ultrasonic Noise Assessment

Ultrasonic haptic technology is one of the more interesting novel technologies being intensively developed in recent years. Such technology has a number of undoubted advantages and potential applications, but it can also be a source of ultrasonic noise. Pursuant to the provisions of the labor law, ultrasonic noise at a high sound pressure level can be a harmful factor for human health. The article presents the results of the assessment of ultrasonic noise emitted by an ultrasonic haptic device and the assessment of exposure to noise of a person using the device. The tests were carried out using one of the haptic devices readily available on the market. Ultrasonic noise emission tests were carried out around the device, at selected points placed on the surface of a hemisphere of a radius of 0.5 m, for various haptic objects. The analyzed parameter was the equivalent sound pressure level in the 1~3 octave band with a center frequency of 40 kHz. Variable sound pressure levels ranged from 96 dB to 137 dB. Noise exposure tests were carried out both using the KEMAR measurement dummy and with test participants of different heights. In most cases, the sound pressure level exceeded 110 dB, and in the worst case it exceeded 131 dB. Comparison of the results of ultrasonic noise assessments with the permissible values of this noise in the working environment shows that in the case of prolonged or improper use of the device, the permissible values may be exceeded.

Tracing the Evolution of Sound in Six Generations of the Chevrolet Corvette

This study presents the noise characteristics of six generations of the Chevrolet Corvette, an iconic American sports car that has undergone technological leaps and design innovations over the years, redefining performance and handling. The research conducted as part of an undergraduate noise control project is meant to study the auditory experiences of drivers, occupants, and pedestrians, considering the implications of improved cabin noise reduction in newer models while examining the changes surrounding powertrain and exhaust expectations in various generations of the model. Focusing on the evolution of sound pressure levels, the study analyzes both interior and exterior sound pressure level data to extract insights into the acoustic metamorphosis of the Corvette. This exploration enhances the understanding of the difference between sound and the Corvette driving experience. The research's significance extends to the community of Corvette enthusiasts, contributing to the historical narrative of this sports car and impacting automotive culture. Anticipation regarding the exterior experience for pedestrians aligns with sentiments about the powertrain and exhaust personality. The study concludes that stock Corvettes, even older models, do not significantly endanger hearing, mainly due to road noise. The interior sound at various speeds and accelerations can reach close to 90dBA periodically. Also, aftermarket exhaust systems hint at the possibility of extremely high sound pressure levels.

Thinking inside the box: a cost-effective approach to fan array noise reduction

Noise from fan arrays can contribute high sound pressure levels both to buildings and communities. Noise that travels from these units through ducts and into the spaces within buildings can be attenuated with silencers or duct lining. However, sound radiated from the unit through building structures or into communities can be more difficult to attenuate and often adds significant cost. While it is possible to attenuate sound from the unit using enclosures or sound walls, exploring the operation of the fan arrays themselves could be a more cost-effective noise reduction method. One particular noise reduction method for an existing fan array was proposed for a customer: review sound levels of each fan within the array to determine how they are contributing to the radiated sound power level of the unit. The assumption that sound levels between individual fans within fan arrays are consistent is not always correct. A series of acoustical tests were completed; results indicated that sound caused by turbulent airflow within the tested fan array was able to be lowered by reducing the fan speeds of individual fans. By reducing the fan speeds of problematic fans and increasing speeds for the quieter ones within the same fan array, the same level of cooling can be provided with lower overall radiated sound levels at no additional cost.

Highly sensitive photoacoustic gas sensor based on near-concentric cavity

The precise detection of trace gases in the atmosphere is vital for both environmental preservation and human health. Addressing the inherent challenges in enhancing the sensitivity of photoacoustic spectroscopy, a highly sensitive photoacoustic gas detection method utilizing a near-concentric cavity was proposed. By constructing a near-concentric optical cavity, laser reflections within the photoacoustic cell were substantially amplified, resulting in enhanced sensitivity of photoacoustic signal detection. Additionally, to align with the optical path characteristics of the near-concentric cavity, a miniaturized dumbbell-like photoacoustic cell was designed. Characterized by its high-frequency resonance, this design effectively mitigated background noise while maintaining a high sound pressure level. Experimental results demonstrated a remarkable enhancement in both signal intensity and signal-to-noise ratio by factors of 22.06 and 21.26, respectively, compared to traditional excitation methods. According to the 1σ standard, with a laser power of 21 mW, the setup achieved a detection limit of 10.15 ppb for NO2. The corresponding normalized noise equivalent absorption was calculated to be 2.84 × 10−9 cm−1WHz−1/2, with a gas consumption rate of merely 15.19 mL.

Aerodynamic and aeroacoustic characteristics of rocket sled under strong ground effect

Rocket sled test avoids boundary effects in wind tunnel test and inconvenience of flight test, which is one of the feasible options for future single-stage-to-orbit. To analyze potential safety issues during payload separation and optimize the arrangement of testing sensors, different structural layouts and operating speeds of the rocket sled are conducted based on computational fluid dynamics and computational aeroacoustics. The hypersonic winged standard model is utilized as the load for these simulations. The analysis encompasses the evolution of shock waves, the forces exerted on the payload and noise propagation. Variations in flow field and aeroacoustic characteristics of rocket sled are analysed, revealing underlying physical mechanisms. It is observed that placing the payload in front of the thruster can reduce the head pressure, excessive wingspan may have an impact on the structural safety of the wingtip, and the regions of high sound pressure levels mainly exists in the middle and rear sections of the rocket sled. Moreover, as the Mach number increases, the characteristic frequency initially rises and then declines. These researches can serve as a valuable reference for the development of ground test systems and single-stage-to-orbit.

An integral wavy shaped P(VDF-TrFE) transducer for audio directional system

To generate self-demodulated low-frequency acoustic waves with high directivity in audio directional system, an integral piezoelectric P(VDF-TrFE) 80/20 mol% film, proving as a typical ferroelectricity and exhibiting the excellent electromechanical coupling factors, is formed into a regular wavy shaped transducer. The frequency response and directivity performances of the large-size transducer are theoretically simulated using COMSOL software, showing that the response is relative smooth over the audio frequency range. As such, the highest sound pressure level is located at a resonant frequency of 40 kHz, while the sound is highly directional and the 3-dB beam-width becomes increasingly sharp with the raise of size of P(VDF-TrFE) film. Interestingly, the integral wavy shaped P(VDF-TrFE) transducer exhibits a sound pressure of 78 dB at 500 mm and the 3-dB beam-widths of 100 Hz,1 kHz, and 6 kHz are ±2.8º, ±3.1º, and ±2.9º, respectively. Thus, the wavy type P(VDF-TrFE) transducer is duplicatable and easy to facilitate extra-large for emerging applications.

Experimental study of a separated shear layer transition under acoustic excitation

The paper discusses experimental results on the effect of broadband acoustic excitation on laminar-to-turbulent transition in a separated shear layer developing on a flat plate subjected to an adverse pressure gradient (APG) and freestream turbulence level equal to Tu ≅ 1 %. The study encompasses the influence of Reynolds number (Rex = 185 000 and 370 000) and sound pressure level (SPL). The inherent complexity of the problem is simplified by providing an acoustic excitation from a controlled source (loudspeaker), acting on the boundary layer developing on the flat plate with a given streamwise pressure gradient. Two types of instabilities were identified in the pre-transitional boundary layer in unexcited flows. One was related to the inviscid Kelvin-Helmholtz (K-H) instability, while the second one was associated with formation of streamwise-oriented Klebanoff streaks (so-called Klebanoff mode).In the low Reynolds number case (Rex = 185 000), the K-H was responsible for transition onset, while in the high Reynolds number flow (Rex = 370 000), the Klebanoff distortions dominated the turbulent breakdown with the minor effect of the K-H instability. In addition to the naturally developing boundary layer, the flow was exposed to a pink noise characterized by SPL = 125 dB and 135 dB. In the low Reynolds number case, the acoustic excitation enhanced the K-H instability. It resulted in an earlier laminar-to-turbulent transition in case with higher sound pressure level (135 dB). In the high Reynolds number flow, the acoustic excitation enhanced the mixed-type transition mechanism with dominant role of the Klebanoff streaks. Shrinking or complete suppression of the separation bubbles was observed, depending on the applied sound pressure level (125 and 135 dB).

Evaluation of Noise Pollution in Residential Areas Under the Influence of Truck Traffic in Ramshir, Khuzestan-Iran

Background & Aims: Noise is one of the types of urban pollution that causes human annoyance. This study aimed at investigating noise pollution in residential areas under the influence of truck traffic in Ramshir in 2023. Materials and Methods: In this applied research, sound parameters were measured by a sound meter capable of measuring the minimum sound level, maximum sound level, equivalent continuous sound level (Leq), and sound pressure level (SPL) of sound parameters at 10 stations in the morning and at night with 3 repetitions. In addition, noise annoyance was determined in 100 people in residential areas exposed to urban noise using the ISO 15666 noise annoyance questionnaire. Measurements were performed over three months in two day and night shifts using a TES-1358C analyzer sound meter device (TES Company, Taiwan). The raw data were entered into SPSS 21 and Excel software and then categorized, and the necessary results were extracted, including the average of the data, as well as the maximum and the minimum of the data. Results: The results revealed that the average SPL was 88.25 dB during the daytime on Tawheed Street, so it had the highest measured sound level compared to other investigated areas. Further, the Leq was 82.17 dB at night in the Shariati area, which had a higher SPL than other areas. The highest Leq of the day was related to Naft Street Station, with an average value of 83.40 dB, while the lowest Leq value attributed to Damghani Street Station was measured with an average value of 71.41 dB. The highest Leq of night noise was related to Shariati Street Station, with an average value of 82.17 dB. The impact of truck noise was highly uncomfortable, uncomfortable, and slightly uncomfortable for 13%, 37%, and 36% of people, respectively. Conclusion: In general, in the range of 10 stations, the SPL and Leq were measured higher at night and day than the standards of the Iranian Environmental Organization and the Environmental Protection Agency (55 dB during the day and 45 dB at night for residential areas). According to the sum of the answers, the sound of the trucks in the intended city could hurt people. People are most dissatisfied with the sound of trucks in the morning and at night.

Numerical prediction and optimization of aerodynamic noise of straw crushers by considering the straw-crushing process

Straw crops are struck and broken into soft filaments by the high-speed rotating hammers of straw crushers, which disturb the internal airflow field and generate much noise during the operation of straw crushers. To accurately estimate and reduce the aerodynamic noise of straw crushers at the design stage, in this study, first, the coupling method of the discrete element method, bonded-particle model, and computational fluid dynamics were used to obtain the acoustics source data. Next, the Ffowcs Williams–Hawkins theory and the indirect boundary element method were used to predict the aerodynamic noise generated during the straw crushing process. The multi-island genetic algorithm was used to optimize the aerodynamic noise of straw crushers. The results indicate that the simulated and measured total sound pressure levels (TSPLs) at the outlet and inlet differed by 1.43 and 2.12 dB(A), respectively. Additionally, aerodynamic noise at the inlet appears to be primarily influenced by the sound pressure level at the excitation fundamental frequency, while noise at the outlet is primarily influenced by the sound pressure level at the double frequency. Higher sound pressure levels were mainly concentrated at the fundamental frequency and its lower harmonic frequencies, and the sound pressure level gradually decreased with the increase in the frequency. After optimization, the aerodynamic noise TSPL at the inlet decreased from 100.87 to 88.58 dB(A) and at the outlet decreased from 102.26 to 89.62 dB(A). This study provides a methodological reference for aerodynamic noise prediction and the design of low-noise straw crushers.

Articulatory and acoustic differences between lyric and dramatic singing in Western classical music.

Within the realm of voice classification, singers could be sub-categorized by the weight of their repertoire, the so-called "singer's Fach." However, the opposite pole terms "lyric" and "dramatic" singing are not yet well defined by their acoustic and articulatory characteristics. Nine professional singers of different singers' Fach were asked to sing a diatonic scale on the vowel /a/, first in what the singers considered as lyric and second in what they considered as dramatic. Image recording was performed using real time magnetic resonance imaging (MRI) with 25 frames/s, and the audio signal was recorded via an optical microphone system. Analysis was performed with regard to sound pressure level (SPL), vibrato amplitude, and frequency and resonance frequencies as well as articulatory settings of the vocal tract. The analysis revealed three primary differences between dramatic and lyric singing: Dramatic singing was associated with greater SPL and greater vibrato amplitude and frequency as well as lower resonance frequencies. The higher SPL is an indication of voice source changes, and the lower resonance frequencies are probably caused by the lower larynx position. However, all these strategies showed a considerable individual variability. The singers' Fach might contribute to perceptual differences even for the same singer with regard to the respective repertoire.

Serum Prestin Level May Increase Following Music Exposure That Induces Temporary Threshold Shifts: A Pilot Study.

To determine if blood prestin level changes after exposure to music at high sound pressure levels, and if this change is associated with temporary threshold shift (TTS) and/or changes in distortion product (DP) amplitude. Participants were exposed to pop-rock music at 100 dBA for 15 min monaurally through headphones. Pure-tone audiometry, DP amplitude, and blood prestin level were measured before and after exposure. Fourteen adults (9 women; age range: 20 to 54 years, median age = 31 [Interquartile ratio = 6.75]) with normal hearing were included in the study. Mean prestin level increased shortly after exposure to music, then returned to baseline within 1 week, although this trend was not observed in all participants. All participants presented TTS or a decrease in DP amplitude in at least one frequency after music exposure. There was a statistically significant average threshold elevation at 4 min postexposure. Statistically significant DP amplitude shifts were observed at 4 and 6 kHz, 2 min following exposure. Mean baseline serum prestin level (mean: 140.00 pg/mL, 95% confidence interval (CI): 125.92 to 154.07) progressively increased following music exposure, reaching a maximum at 2 hr (mean: 158.29 pg/mL, 95% CI: 130.42 to 186.66) and returned to preexposure level at 1 week (mean: 139.18 pg/mL, 95% CI: 114.69 to 163.68). However, after correction for multiple comparisons, mean prestin level showed no statistically significant increase from baseline at any timepoint. No correlation between maximum blood prestin level change and average TTS or distortion product otoacoustic emission amplitude shift was found. However, in an exploratory analysis, TTS at 6 kHz (the frequency at which maximum TTS occurred) decreased significantly as baseline blood prestin level increased. The results suggest that blood prestin level may change after exposure to music at high sound pressure levels, although statistical significance was not reached in this relatively small sample after correction. Baseline serum prestin level may also predict the degree of TTS. These findings thus suggest that the role of baseline serum prestin level as a proxy marker of cochlear susceptibility to intense music exposure should be further explored.

Sound attenuation performance at high sound pressure level of micro-perforated panel sound absorber with embedded resistive screen

In this paper, a composite sound absorber made of a micro-perforated panel (MPP), an air cavity with embedded resistive screen and a rigid back plate is investigated at high sound pressure level (SPL). The sound absorption coefficient predicted theoretically is compared with the experimental measurement at 150 dB and a good agreement is obtained. It is demonstrated that the incorporation of resistive screen within the air cavity improves significantly the sound absorption that presents a large frequency band and remains almost identical with respect to the SPL compared to a classical MPP absorber whose sound absorption peak varies with the SPL. The MPP absorber with the resistive screen glued on the MPP is studied and different resistive screens are compared at 150 dB and it is observed that the sound absorption coefficient increases with a large frequency band, which depends on the airflow resistivity of the screen. A sensitivity analysis shows that the resistance per unit area of the screen affects the acoustic properties of the absorber at low SPL while at high SPL, the acoustic properties are mainly controlled by the perforation ratio of the MPP and the acoustic orifice Mach number.

Comprehensive analysis of the seismic wave fields generated by offshore pile driving: A case study at the BARD Offshore 1 offshore wind farm.

Offshore pile driving not only generates high sound pressure levels, but also induces ground vibrations and particle motions that have the potential to affect fish and invertebrates living near or in the seabed. In particular, the seismic wave field in the form of interface waves is thought to be responsible for causing these particle motions and ground vibrations. However, the magnitude and spatial extent of the seismic wave field resulting from pile driving has not been clearly established. To fill this knowledge gap, this paper analyzes and illustrates in detail the seismic wave field at a construction site of the BARD Offshore 1 wind farm. For this purpose, the measured data from the construction site are compared to the results of a seismo-acoustic model. The measured and modeled data in combination provides a potential benchmark case for subsequent studies and other authors. The computed seismic wave field is investigated in terms of wave generation, mode composition, and propagation range of individual modes. The different seismic wave forms and their contribution to the particle motions in the seabed vicinity are discussed. The results indicate that, for the considered case, interface waves dominate the particle motion at the seafloor level up to a distance of 200 m.

Modelling the Propagation of Underwater Acoustic Signals of a Marine Energy Device Using Finite Element Method

Today a large number of marine based energy devices are been deployed rapidly across coastal areas of the world’s oceans to harness the huge natural energy and power potential provided by nature. These devices produce sound signals at high sound pressure levels across a wide range of frequencies that could be detrimental to the health and livelihood of marine animals. This paper proposes a computer model that simulates the emission of acoustic signals produced by a wave energy device. It analyses these signals with the aid of the audiogram of marine mammals, in this case the Harbour seal. This enables us to estimate the levels of acoustic noise experienced by marine mammals due to the presence of ocean deployed devices. Propagation of the acoustic signals underwater was modelled with boundary conditions using the finite element method. These include the bathymetry (features of underwater terrain) of the deployment site and properties of the propagation media. The type of spreading of the acoustic signals, and their interaction with the bottom surface interface of the acoustic enviroment was also taken into consideration. The effect of the bottom surface of the acoustic medium was seen to affect the sound pressure level (SPL) values as the sound receiver moves away from the source.