Relative Sound Pressure Level Research Articles

Laboratory Validation of 3D Model and Investigating Its Application to Wind Turbine Noise Propagation over Rough Ground

In an investigation into how wind turbine noise interacts with the surrounding terrain, its propagation over rough ground is simulated using a parabolic equation code using a modified effective impedance model, which characterizes the effects of a three-dimensional, rigid roughness within a relatively long wavelength limit (ka≤1). The model is validated by comparison to experiments conducted within an anechoic chamber wherein different source–receiver geometries are considered. The relative sound pressure level spectra from the parabolic equation code using the modified effective impedance model highlight a sensitivity to the roughness parameters. At a low frequency and far distance, the relative sound pressure level decreased as the roughness coverage increased. A difference of 4.9 dB has been reported. The simulations highlight how the roughness shifts the ground effect dips, resulting in the sound level at the distance of 2 km being altered. However, only the monochromatic wave has been discussed. Further work on broadband noise is desirable. Furthermore, due to the long wavelength limit, only a portion of audible wind turbine noise can be investigated.

Do Acoustic Characteristics of Dysarthria in People With Parkinson's Disease Differ Across Languages?

Cross-language studies suggest more similarities than differences in how dysarthria affects the speech of people with Parkinson's disease (PwPD) who speak different languages. In this study, we aimed to identify the relative contribution of acoustic variables to distinguish PwPD from controls who spoke varieties of two Romance languages, French and Portuguese. This bi-national, cross-sectional, and case-controlled study included 129 PwPD and 124 healthy controls who spoke French or Portuguese. All participants underwent the same clinical examinations, voice/speech recordings, and self-assessment questionnaires. PwPD were evaluated off and on optimal medication. Inferential analyses included Disease (controls vs. PwPD) and Language (French vs. Portuguese) as factors, and random decision forest algorithms identified relevant acoustic variables able to distinguish participants: (a) by language (French vs. Portuguese) and (b) by clinical status (PwPD on and off medication vs. controls). French-speaking and Portuguese-speaking individuals were distinguished from each other with over 90% accuracy by five acoustic variables (the mean fundamental frequency and the shimmer of the sustained vowel /a/ production, the oral diadochokinesis performance index, the relative sound level pressure and the relative sound pressure level standard deviation of the text reading). A distinct set of parameters discriminated between controls and PwPD: for men, maximum phonation time and the oral diadochokinesis speech proportion were the most significant variables; for women, variables calculated from the oral diadochokinesis were the most discriminative. Acoustic variables related to phonation and voice quality distinguished between speakers of the two languages. Variables related to pneumophonic coordination and articulation rate were the more effective in distinguishing PwPD from controls. Thus, our research findings support that respiration and diadochokinesis tasks appear to be the most appropriate to pinpoint signs of dysarthria, which are largely homogeneous and language-universal. In contrast, identifying language-specific variables with the speech tasks and acoustic variables studied was less conclusive.

Effects of Mouthpiece Noninvasive Ventilation on Speech in Men With Muscular Dystrophy: A Pilot Study.

Purpose The use of noninvasive ventilation (NIV) is on the rise as an alternative to tracheostomy for individuals with neuromuscular disorders with life-prolonging and quality-of-life benefits. This pilot study was designed to determine if mouthpiece NIV (M-NIV) alters speech in individuals with muscular dystrophy (MD). Method Eight men (23-44 years), seven with Duchenne MD and one with Becker MD, who used daytime M-NIV, were asked to sustain phonation, count, and read under three conditions: (a) Uncued (no instructions), (b) With M-NIV (cued to use M-NIV with all speaking breaths), and (c) Without M-NIV (as tolerated). Breath group and inspiratory durations, syllables/breath group, and relative sound pressure level were determined from audio and video recordings. Results Uncued condition: Participants used the ventilator for all inspirations that preceded sustained phonation and counting. During reading, four participants used M-NIV for all inspirations, one never used it, and three used it for some (19%-41%) inspirations. With- versus Without-M-NIV conditions: Breath group duration was significantly longer across all tasks, syllables per breath group were significantly greater during reading, and inspiratory pause duration during reading was significantly longer with M-NIV than without. Sound pressure level was significantly higher during the first second of sustained phonation with M-NIV (though not for counting and reading). Two participants were unable to complete the reading task audibly without using their M-NIV. Conclusions Speech may be better with M-NIV than without because it is possible to produce longer breath groups and some people with severe respiratory muscle weakness may not be able to speak at all without ventilator-supplied air. Nevertheless, the longer inspiratory pauses that accompany M-NIV may interrupt the flow of speech. Future research is needed to determine the most effective way to use M-NIV for speaking and whether training participants in its use can bring even greater speech benefits.

Acoustic-Perceptual Correlates of Voice Among Steam Train Engineers: Effects of Noise and Hearing Protection

Occupational voice users are at a higher risk for developing voice disorders due to their vocal demands, such as prolonged periods of work-related voice use and nonideal environmental factors, such as speaking above background noise. The current study focused on the effects of background noise and hearing protection on acoustic-perceptual correlates of voice among steam train engineers. Fourteen participants phonated vowel /a/, read a phrase, and described a map under different noise and hearing protection conditions. Relative sound pressure level, relative fundamental frequency, and perceived vocal effort and disturbance decreased in the presence of hearing protection for all noise conditions. In contrast, these acoustic measures increased in the absence of hearing protection supporting Lombard effect. Overall, results of the current study provide insight into possible risks to vocal health in workers exposed to high levels of background noise and use hearing protection.

Comparative Evaluation of Ray Tracing and Diffusion Equation Modeling in Room Acoustics Design of Subway Stations

Due to their disproportionate geometries and uneven distribution of sound, the interior sound field analysis of subway stations has always been challenging. The field necessitates reliable tools for real-case design applications, while the research and discussions on the topic are still ongoing. This study compares two major room acoustics simulation approaches, namely ray tracing and diffusion equation modeling (DEM) in order to assist future acoustical designs of subway stations. Two cases of Istanbul Metropolitan metro lines are selected, namely station BAG with a circular cross section and station USK with rectangular cross section. The reverberation time and relative sound pressure level results from field tests are compared with those obtained by the ray tracing and DEM. The results emphasized the validity as well as limitations of each method over discussed metrics with given geometric layouts and material characteristics of the subway stations.

Vocal Fatigue in Prospective Vocal Professionals

The goals of the study were to (a) examine vocal fatigue in speech-language pathology students through subjective and objective measures following a novel 30-minute vocal loading task (VLT) and (b) evaluate the effects of psychosocial factors on vocal fatigue. Seventeen speech-language pathology students completed a 30-minute VLT using the LingWAVES software program. In addition to maintaining target intensity goals during reading a text, participants were also required to modify their pitch and voice quality. Vocal fatigue was measured subjectively using Vocal Fatigue Index and Borg vocal effort scale and objectively using variations of relative sound pressure level, fundamental frequency, pitch strength, smoothed cepstral peak prominence (CPPS), and acoustic voice quality index before, during, and after VLT. Participants provided information on their sleep quantity, stress, and depression through nonstandardized and standardized surveys. Results revealed that perceived effort and fatigue increased significantly after the 30-minute VLT. Acoustic measures of relative sound pressure level and fundamental frequency and increased systematically during and after the completion of task. All students were moderately stressed and measures related to pitch were highly related with perceived stress. The results of this study provide support for altering multiple vocal parameters to induce measurable changes in vocal fatigue following a short-duration VLT.

How well do acoustic recordings characterize properties of bee (Anthophila) floral sonication vibrations?

ABSTRACTFloral sonication is a behaviour in which certain bees generate substrate-borne vibrations by contracting their flight muscles in order to extract pollen from poricidal anthers. Sonication vibrations, or ‘buzzes’, also contain a corresponding audible sound that results from vibrations radiating from the exoskeleton into the surrounding air. Acoustic recordings are often used as a proxy for analysis of floral sonication vibrations because they are more accessible to recording with conventional equipment such as microphones. However, the extent to which salient parameters of buzzes are reflected in the airborne components has not been experimentally verified. We examined correspondence in three properties (duration, frequency and amplitude) simultaneously recorded with acoustic and vibrational methods from freely foraging bumblebees. Duration and frequency are faithfully quantified from airborne recordings; however, two measures of acoustic amplitude (relative peak amplitude and sound pressure level) are not correlated with vibrational amplitude. Our findings validate acoustic recordings as a method to describe temporal and spectral components of floral sonication vibrations, but we caution against using acoustic measures of amplitude as proxies for the true vibrational power.

Listening in the bog: II. Neural correlates for acoustic interactions and spacing between Sphagniana sphagnorum males

Males of the katydid Sphagniana sphagnorum maintain inter-male distances from one another using agonistic song interactions with a frequency-modulated song that consists of alternating audio and ultrasonic parts. We studied the neuronal representation of this song in auditory receptors and interneurons of receivers, using playbacks of songs that mimicked the absolute and relative sound pressure levels of the two song modes varying with distance. The tuning and sensitivity of both receptors and interneurons strongly determine their responses to the two song modes at different distances. Low-frequency interneurons respond preferentially to the audio mode of the song at larger distances. High-frequency (HF) interneurons respond preferentially to the HF component of the song at close range. ‘Switch interneurons’ are sensitive to both spectral song components, but exhibit a typical activity switch towards the high-frequency mode at distances nearer than 3–6 m. The activity of the latter two groups of interneurons correlates with the distance in the field at which males begin to interact acoustically with their neighbours. Important information about the rate of changes in the song mode is represented by the afferent activity despite the influence of the masking song produced by a sympatric katydid species.

Numerical modeling of acoustic propagation in Harbor porpoise’s (Phocoena phocoena) head

Harbor porpoises (Phocoena phocoena) use narrow band echolocation signals for locating prey and spatial orientation. In this study, acoustic impedance values of tissues in the porpoise’s head were calculated from the Hounsfield Units (HU). A two-dimensional finite element model was set up base on the computed tomography (CT) scan data to simulate the acoustic propagation through animal’s head. The far field transmission beam pattern in the vertical plane and the waveforms of the receiving points around the forehead were compared with prior measurement results, the simulation results were qualitatively consistent with the measurement results. The role of the main structures in the head such as air sacs, melon and skull in the acoustic propagation was investigated. Additionally, the relative sound pressure level within the porpoise’s sonar field across the transitional near and far field was obtained to compare with the spherical spreading loss.

Inclusion of source extent and coherence in a finite-impedance ground reflection model with atmospheric turbulence

Acoustic data collected in static rocket tests are typically influenced by ground reflections. Furthermore, the partial coherence of the ground interaction due to atmospheric turbulence can play a significant role for larger propagation distances. Because the rocket plume is an extended radiator whose directionality is the result of significant source correlation, assessment of the impact of ground reflections in the data must include these effects. In this paper, a finite impedance-ground, single-source interference approach [G. A. Daigle, J. Acoust. Soc. Am. 65, 45–49 (1979)] that incorporates both amplitude and phase variations due to turbulence is extended to distributions of correlated monopoles. The theory for obtaining the mean-square pressure from multiple correlated sources in the presence of atmospheric turbulence is described. The effects of source correlation and extent, ground effective flow resistivity, and turbulence parameters are examined in terms differences in relative sound pressure level across a realistic parameter space. Finally, the model prediction is compared favorably against data from horizontal firings of large solid rocket motors. [Work supported by NASA MSFC and Blue Ridge Research and Consulting, LLC.]

Spectral Optimization of Fan Rotation Noise Based on Vector Composition Method

In order to optimize the rotation noise spectrum of vehicle alternator cooling fan, a Vector Composition Method was proposed. Based on this method, the relative sound pressure level (RSPL) variations were calculated, which were then used as parameters in the optimization of spectral structure. In this article, the sound pressure level (SPL) variations of the 12thand 18thorder (of rotation frequency) who had the most prominent fan rotation noises were set as optimization targets, the blade distribution angles were optimized to ameliorate the spectral structure and the distribution of spectral energy. Calculations showed that, the RSPL in orders 12 and 18 were decreased by 9.3dBA and 10.5dBA respectively, comparing with experiment results, the errors were 3.9% and 4.11% respectively. Results suggested that the rotation noise of target orders had been significantly diminished, so the objective of optimizing spectral structure was reached. This method has a guiding significance to the design of blade distribution angles.

Numerical Laser Energy Deposition on Supersonic Cavity Flow and Sensor Placement Strategies to Control the Flow

In this study, the impact of laser energy deposition on pressure oscillations and relative sound pressure levels (SPL) in an open supersonic cavity flow is investigated. Laser energy with a magnitude of 100 mJ is deposited on the flow just above the cavity leading edge and up to 7 dB of reduction is obtained in the SPL values along the cavity back wall. Additionally, proper orthogonal decomposition (POD) method is applied to the x-velocity data obtained as a result of computational fluid dynamics simulations of the flow with laser energy deposition. Laser is numerically modeled using a spherically symmetric temperature distribution. By using the POD results, the effects of laser energy on the flow mechanism are presented. A one-dimensional POD methodology is applied to the surface pressure data to obtain critical locations for the placement of sensors for real time flow control applications.

Investigation of Fatigue, Delayed-Onset Muscle Soreness, and Spectral-Based Cepstral Measurements in Healthy Speakers after Neuromuscular Electrical Stimulation

We observed whether 30 minutes of neuromuscular electrical stimulation applied to the necks of healthy speakers would result in significant acoustic changes and perceptions of fatigue and/or delayed-onset muscle soreness (DOMS). Twelve participants were assigned to experimental (n=6; 3 male and 3 female) and control groups (n=6; 3 male and 3 female). Neuromuscular electrical stimulation was applied to the anterior neck in the experimental group only. All participants produced 3 trials of the vowel /a/ and the Rainbow Passage before and after completing a 30-minute phonation protocol. Recorded samples were analyzed for measures of the cepstral peak prominence, the ratio of low- to high-frequency spectral energy, and their respective standard deviations. Perceptions of fatigue and DOMS were rated on visual analog scales before, 5 minutes after, and 24 hours after completion of the phonation protocol. Statistically significant acoustic findings reflecting reduced relative sound pressure level, increased high-frequency noise, and phonatory instability were observed in the experimental group. In addition, reports of fatigue and DOMS were also reported by some participants. A 30-minute dosage may be too high for some people experiencing neuromuscular electrical stimulation for the first time.

Research on the Simulation of the Subjective Annoyance of Actual Noise Using Combined Pure Tones

A number of typical noise sources from urban environments were recorded. Based on spectral analysis, several characteristic frequencies which involved high subjective annoyance were selected according to the relative subjective annoyance of pure tones with different frequencies at equal loudness levels. Pure tones with characteristic frequencies were synthesized into a series of noise samples. A paired comparison test was used for comparison of the subjective annoyance due to actual noise and synthesized noise. The results suggest that the sound energy distribution of actual noise at different frequency bands should be considered in order to simulate the subjective annoyance induced by actual noise with composite noise more accurately. Composite noise should be combined with pure tones which induced high subjective annoyance and are located in frequency bands with the majority of sound energy, provided that the relative Sound Pressure Level (SPL) differences among the characteristic frequencies of actual noise were retained.

Leakage identification for a vehicle firewall sound transmission by beamforming technique.

The acoustic phased array is a powerful tool for identification and quantification of noise sources on complex systems. Acoustic sources generate waves which propagate through space to the N microphones of the array. The acoustic pressures are sampled and converted to time series data and processed using either time domain or frequency domain delayed and averaged. The output of signal processing is a colored image with relative sound pressure levels distribution. In this paper application of beamforming technique is used to identify leakage areas in a vehicle firewall. Two acoustic rooms are used and the firewall was installed in the apertures inbetween with careful control of noise flank paths. Source room was excited with white noise and a phased array microphone was used to measure the sound field in the anechoic receiving room. The firewall was evaluated both with all holes sealed and with the regular pass‐through components installed. Two different acoustic insulators were also tested on the firewall. The results show clearly the areas of leakage with relative noise levels at each test configuration.

Aerodynamic Assessment of Young Women’s Voices as a Function of Oral Contraceptive Use

Objective: To examine possible differences in glottal airflow parameters according to oral contraceptive (OC) use. Subjects and Methods: The participants included 16 women, 20–24 years of age. Eight women were taking a triphasic OC; the remaining 8 women were not taking any form of oral contraception (NOC). All participants were recorded on days 7 and 14 of their menstrual cycle. Three repetitions of the sustained vowel /a/ were obtained using a circumferentially vented respiratory face mask connected to a wide-band pressure transducer. Measures of peak flow, minimum flow, alternating flow, fundamental frequency (F₀) and relative sound pressure level were obtained. Results: A multivariate analysis of variance with sound pressure level as a covariate revealed no significant effect of day of recording upon the dependent measures. As a group, the OC women exhibited significantly higher F₀, peak and alternating flow rates compared to the NOC women. Removal of data outliers from the OC women resulted in similar airflow rates for both groups. Conclusion: The findings from this preliminary study did not support the use of glottal airflow measures to distinguish OC women from NOC women. Differences in F₀ findings may reflect hormonally mediated changes in laryngeal tissue and warrant further investigation.

Evaluations of output from room acoustic computer modeling and auralization due to different sound source directionalities

Evaluations of the predictions and auralizations from the room acoustic modeling program, ODEON, have been run using three directional source types with the same sound power: (a) an omni-directional source; (b) three sources with realistically-directional characteristics based on measurements from real instruments (grand piano, violin, and singing voice); and (c) an artificial, extremely directional beaming source. Objective analyses have been run for nine source/receiver combinations in a simple hall on three acoustic parameters: relative sound pressure level (SPL), reverberation time (T30), and clarity index (C80). Auralizations were subsequently created for two source/receiver combinations and used in subjective testing with 28 subjects. Results show that, objectively, differences in SPL were negligible for the majority of cases. Some differences in T30 and C80 were found between the omni-directional and realistically-directional sources; however, subjects did not perceive any corresponding differences when comparing the auralizations, possibly due to the limited directional octave band data available. Subjects did significantly differentiate between auralizations from the omni-directional source and the extreme beaming source. Subjective results from comparing these two sources in terms of reverberation, clarity and realism were generally consistent with objective data, although source/receiver combination and musical track had some influence on the outcomes.

Room volume estimation from diffuse field theory

Among the parameters relevant in room acoustics, the room volume is one of the most important. The general course in room acoustics research is to use the room volume in the prediction of room acoustic parameters such as reverberation time or total relative sound pressure level. Contrary to this, it has been investigated to what extent the room volume can be retrieved from a measured room impulse response. The approach followed is based on room acoustic diffuse field theory and requires correctly measured room impulse responses with the initial time delay corresponding to the source to receiver distance. A total of ten rooms of varying size and acoustic characteristics have been included. The results in three rooms were unreliable, which was explained by the particular acoustic characteristics. In the remaining rooms the results were numerically useful and consistent between different positions within the same room (relative standard deviation around 20%). The influence of source and receiver directivity is also considered.

Method of controlling the auditory response of wireless devices

Cellular telephones, pagers, PDAs, and other wireless devices, are configured to network together when in close proximity with each other, measure the relative sound pressure level of their environment, and modify the auditory response of the wireless device based on established parameters. In this way, a wireless device may detect when it is in a quiet room with multiple other devices, which is indicative of a meeting that should not be disturbed, and thus defeat or modify its behavior to reduce interruptions of group events.

Reflection of sound from random distributions of semi-cylinders on a hard plane: models and data

A new analytical theory for multiple scattering of cylindrical acoustic waves by an array of finite impedance semi-cylinders embedded in a smooth acoustically hard surface is derived by extending previous results for plane waves (Linton and Martin 2005 J. Acoust. Soc. Am. 117 3413–23). Although the computational demands of the new theory increase as the number of the semi-cylinders in the arrays and/or the frequency increase, the theory offers an improvement on analytical boss theories since the latter (i) are restricted to non-deterministic (infinite) random distributions of semi-cylinders with spacing/radii small compared to the incident wavelength and (ii) are derived only for plane waves. The influence on prediction accuracy of truncation of the infinite system of equations introduced by the new theory is explored empirically. Laboratory measurements have been made over deterministic random arrays of identical varnished wooden semi-cylinders on a glass plate. The agreement between predictions and measured relative sound pressure level spectra is good both for single deterministic random distributions and for averages representing non-deterministic random distributions. The analytical theory is found to give identical results to those of a boundary element calculation but is much faster to compute.