Peak Sound Pressure Level Research Articles

Uncertainty of ANSI/ASA S12.42 Hearing Protection Device Impulsive Measurements

ANSI/ASA S12.42 was extended in 2010 to include methods for measuring the performance of hearing protection devices (HPDs) in impulsive noise conditions. The standard specifies the instrumentation, methods, and data analysis required to measure impulse peak insertion loss (IPIL). IPIL is defined as the amount by which an HPD reduces the effective peak level of an impulsive sound. To characterize HPDs whose attenuation may be level-dependent, IPIL is measured at several impulse peak sound pressure levels, typically in the range of 130-170 dB. Factors contributing to the uncertainty of IPIL measurements include repeatability in the generation of test impulses, variability of the HPD samples under test and their repeated fitting to the test fixture, and spectral properties of the impulse source and the HPD’s attenuation. To help inform future revisions to the S12.42 standard, we quantify IPIL measurement uncertainty for a variety of HPDs tested with two different impulsive sound sources. End users of HPDs should be educated about the uncertainty inherent in IPIL assessments of HPD performance.

Acoustic and heat release signatures for swirl assisted distributed combustion

The acoustic signal and heat release fluctuations are examined from a swirl combustor using methane as the fuel. The focus was on flame stability and noise emission that have direct relevance in further developing distributed combustion for gas turbine applications and oxy-fuel combustion. Three regimes are examined in this paper, the first being a swirl mode at equivalence ratios between 0.9 and 0.55. The second one being distributed combustion, achieved through N2/CO2 dilution to reach oxygen concentration below 15%, fostering distributed reaction. The third was oxy-fuel flame using increased amounts of CO2 dilution to reach distributed reaction. For the first case, lowering the equivalence ratio led to a reduction in the peak sound pressure level around 500Hz and a decrease in heat release fluctuations. For all the equivalence ratios, close coupling between acoustic signature and heat release fluctuations existed around 200Hz. Distributed combustion, achieved at oxygen concentration below 15%, showed a much lower peak sound pressure levels at the 500Hz range with no coupling between heat release fluctuations and acoustic signal, outlining the flame stability at this regime. Also, the noise emission levels were significantly reduced under this mode. For the third regime, increase in CO2 dilution resulted in high heat release fluctuations and an unstable flame which oscillated between two different flame modes, a feature that did not exist in the first two regimes. Further increase in CO2 led to achieving distributed reaction and a much more stable flame as compared to its oscillatory behavior at lower CO2 amounts, along with reduced noise emission levels. This outlines the possibility of achieving distributed combustion in a stable manner via CO2 dilution in oxy-fuel flames.

Passive Acoustic Observations in the Shallow Waters of Northwest Bay of Bengal to Study the Effects of Impact Pile Driving on Fish Chorus

AbstractAmbient noise time series measurements were recorded in the shallow water of Northwest Bay of Bengal. A few data sets revealed the presence of impact pile-driving noise. The site is also known for the presence of the speciesTerapon theraps(Family:Terapontidae), and the fish chorus was recorded during the measurement period. Sound metrics of impact pile-driving noise were calculated to assess their potential impacts on fish chorus. Averaged peak sound pressure level reached 162 dB re 1 μPa, and single-strike sound exposure level is about 134 dB re 1 μPa2s, leading to a cumulative sound exposure level of approximately 148 dB re 1 μPa2s. The impact pile-driving signal has the highest energy in lower frequency band over 0.05‐1 kHz. It is observed thatT. therapsfish chorus also displays their pulse repetition rate and swimbladder spectral peaks at lower frequencies. Detailed analysis of the entire data sets indicates that the fishes were exposed to the pile-driving noise, which would have an impact on the chorus made by them.

Intracochlear Pressure Transients During Cochlear Implant Electrode Insertion.

Cochlear implant (CI) electrode insertion into the round window induces pressure transients in the cochlear fluid comparable to high-intensity sound transients. Many patients receiving a CI have some remaining functional hearing at low frequencies; thus, devices and surgical techniques have been developed to use this residual hearing. To maintain functional acoustic hearing, it is important to retain function of any hair cells and auditory nerve fibers innervating the basilar membrane; however, in a subset of patients, residual low-frequency hearing is lost after CI insertion. Here, we test the hypothesis that transient intracochlear pressure spikes are generated during CI electrode insertion, which could cause damage and compromise residual hearing. Human cadaveric temporal bones were prepared with an extended facial recess. Pressures in the scala vestibuli and tympani were measured with fiber-optic pressure sensors inserted into the cochlea near the oval and round windows, whereas CI electrodes (five styles from two manufacturers) were inserted into the cochlea via a round window approach. Pressures in the scala tympani tended to be larger in magnitude than pressures in the scala vestibuli, consistent with electrode insertion into the scala tympani. CI electrode insertion produced a range of pressure transients in the cochlea that could occur alone or as part of a train of spikes with equivalent peak sound pressure levels in excess of 170 dB sound pressure level. Instances of pressure transients varied with electrode styles. Results suggest electrode design, insertion mechanism, and surgical technique affect the magnitude and rate of intracochlear pressure transients during CI electrode insertion. Pressure transients showed intensities similar to those elicited by high-level sounds and thus could cause damage to the basilar membrane and/or hair cells.

Peak Sound Pressure Levels and Associated Auditory Risk from an H2–Air “Egg-Splosion”

The noise level from exploding chemical demonstrations and the effect they could have on audiences, especially young children, needs attention. Auditory risk from H2–O2 balloon explosions have been studied, but no studies have been done on H2–air “egg-splosions”. The peak sound pressure level (SPL) was measured for the first time and compared to the recommended SPL limits and some recently published work. All peak SPL results ended above 125 dB, some greater than 150 dB. The SPL results exceeded the World Health Organization (WHO) safe limits of 120 dB for children and 140 dB for adults.

Uncertainty of hearing protector impulsive attenuation measurements

Measurement of the impulsive protection of a hearing protection device (HPD) is currently standardized in ANSI/ASA S12.42-2010 as a measurement of impulse peak insertion loss (IPIL). IPIL is a time-domain metric, determined as the difference between open-ear and occluded-ear peak sound pressure levels of an impulse, measured without and with an HPD in place on an acoustic test fixture. To characterize potential level-dependent protection of an HPD, the IPIL test is repeated at several free-field impulse peak sound pressure levels, typically ranging from approximately 130-170 dB. Based on our experiences measuring IPIL with both a shock tube and a rifle serving as the impulse source, as well as a review of existing literature reporting IPIL studies, we discuss and attempt to quantify the uncertainty of such measurements. Sources of uncertainty include the repeatability of the impulse source, characteristics of the sound field created by the impulse source, spectral characteristics of both the impulse source and the HPD’s attenuation, variability between HPD samples and repeat fitting of the HPD to the acoustic test fixture, and variability in the measurement instrumentation and data analysis procedures. Our estimates will be compared to those provided in the uncertainty annex of S12.42.

Concurrent measures of contralateral suppression of transient-evoked otoacoustic emissions and of auditory steady-state responses.

Contralateral suppression of otoacoustic emissions (OAEs) is frequently used to assess the medial olivocochlear (MOC) efferent system, and may have clinical utility. However, OAEs are weak or absent in hearing-impaired ears, so little is known about MOC function in the presence of hearing loss. A potential alternative measure is contralateral suppression of the auditory steady-state response (ASSR) because ASSRs are measurable in many hearing-impaired ears. This study compared contralateral suppression of both transient-evoked otoacoustic emissions (TEOAEs) and ASSRs in a group of ten primarily older adults with either normal hearing or mild sensorineural hearing loss. Responses were elicited using 75-dB peak sound pressure level clicks. The MOC was activated using contralateral broadband noise at 60 dB sound pressure level. Measurements were made concurrently to ensure a consistent attentional state between the two measures. The magnitude of contralateral suppression of ASSRs was significantly larger than contralateral suppression of TEOAEs. Both measures usually exhibited high test-retest reliability within a session. However, there was no significant correlation between the magnitude of contralateral suppression of TEOAEs and of ASSRs. Further work is needed to understand the role of the MOC in contralateral suppression of ASSRs.

Experimental investigation on noise radiation characteristics of pulse detonation turbine engine

The noise radiation characteristics of two-phase pulse detonation combustor and pulse detonation turbine engine were investigated under different operating frequencies utilizing gasoline as fuel and air as oxidizer. The sound pressure data of noise radiation were presented for both single-pulse detonation combustor tube and pulse detonation turbine engine. The experimental results implied that the peak sound pressure level of PDTE exit with inner diameter being 60 mm was about 157 dB under the operating frequencies which varied from 5 Hz to 25 Hz, while the peak sound pressure level of single-pulse detonation combustor tube exit was about 170 dB under the same condition. The far-field jet-noise measurements of the pulse detonation turbine engine showed that radial turbine interacting with the pulse detonation combustor could decrease the peak sound pressure level of pulse detonation combustor with the maximum acoustic attenuation being approximately 14.2 dB for the current test conditions, which could be contributed to the energy extraction by the radial turbine from the pulse detonation combustor exhaust flow. The sound pressure level of both pulse detonation combustor and pulse detonation turbine engine exit was function of directivity angle from the exhaust centerline. In all the experiments, the equivalence ratio of gasoline/air mixture and the fill fraction were 1.2 and 1.0, respectively.

Experiments on Jet Noise Reduction with a Liquid Column

A liquid column is designed and placed into the tail tube to effectively reduce the gas jet noise of a single rocket. The diffusion and mixing process of high-temperature high-pressure gas flow in the liquid water column in the air is studied by means of a high speed photographic system. The gas–liquid mixture jet noise has also been measured. The experimental results indicate that, when the liquid water column is put into the tail tube, the jet flow structure is changed and the jet flow parameters (velocity, temperature, etc.) are decreased due to the interaction of the gas jet with the liquid column. In addition, the jet noise is significantly reduced in the presence of the liquid column, compared with the condition without the liquid column. When the mass of the liquid column increases to 1.485 kg, the jet noise is reduced to a minimum in the shooter location. The peak sound pressure level also decreases with increasing polar angle. Most importantly, the thrust performance of the rocket engine is maintained when the liquid column is introduced.

Assessment of noise exposure for basketball sports referees

ABSTRACTDosimetric measurements carried out on basketball referees have shown that whistles not only generate very high peak sound pressure levels, but also play a relevant role in determining the overall exposure to noise of the exposed subjects. Because of the peculiar geometry determined by the mutual positions of the whistle, the microphone, and the ear, experimental data cannot be directly compared with existing occupational noise exposure and/or action limits.In this article, an original methodology, which allows experimental results to be reliably compared with the aforementioned limits, is presented. The methodology is based on the use of two correction factors to compensate the effects of the position of the dosimeter microphone (fR) and of the sound source (fS). Correction factors were calculated by means of laboratory measurements for two models of whistles (Fox 40 Classic and Fox 40 Sonik) and for two head orientations (frontal and oblique).Results sho w that for peak sound pressure levels the values of fR and fS, are in the range −8.3 to −4.6 dB and −6.0 to −1.7 dB, respectively. If one considers the Sound Exposure Levels (SEL) of whistle events, the same correction factors are in the range of −8.9 to −5.3 dB and −5.4 to −1.5 dB, respectively.The application of these correction factors shows that the corrected weekly noise exposure level for referees is 80.6 dB(A), which is slightly in excess of the lower action limit of the 2003/10/EC directive, and a few dB below the Recommended Exposure Limit (REL) proposed by the National Institute for Occupational Safety and Health (NIOSH). The corrected largest peak sound pressure level is 134.7 dB(C) which is comparable to the lower action limit of the 2003/10/EC directive, but again substantially lower than the ceiling limit of 140 dB(A) set by NIOSH.

The reduction of gunshot noise and auditory risk through the use of firearm suppressors

Law enforcement, security, and military personnel train with small-caliber firearms that present a significant risk of noise induced hearing loss for the operator and range instructors. Measurements of three rifles and one pistol equipped with suppressors were conducted at an outdoor firing range using subsonic and supersonic ammunition. Suppressed and unsuppressed recordings were analyzed. Microphones were located to the left of the muzzle, to the right and left of the shooter’s head, and one meter behind the shooter’s head at the nominal instructor’s position. Recordings were collected with a National Instruments PXI 1082 chassis with an NI 4499 data acquisition board at a 200 kHz sampling rate. Analysis of the peak sound pressure levels (dB SPL) and 8-h equivalent A-weighted energy (LAeq8) were conducted. The suppressors reduced the peak between 15 and 25 dB SPL and the LAeq8 between 8 and 28 dB. Reduced noise levels at the source will reduce auditory risk but do not necessarily eliminate the need for hearing protection. An outdoor noise propagation model based on ISO 17201-1 will be used to investigate the effect of suppressors to reduce noise in surrounding communities.

Factors affecting sound exposure from firing an SA80 high-velocity rifle

The effect of distance on the peak sound pressure level and sound exposure level from an SA80 rifle has been investigated. Sound pressure waveforms were measured in two directions from the gun: downrange, from 50m to 300m, and to the left-hand side, from 0.3m to 32m. Some additional measurements were made to the right of the gun. Measurements made downrange showed three distinct features of the waveform; the shock wave from the supersonic bullet, the reflection from the ground, and the muzzle blast. The time elapsed between the shock wave and the muzzle blast increased with increasing distance: 94ms for a distance of 50m, and 507ms for a distance of 300m. The highest peak sound level downrange from a single round was between 151dB(C) and 148dB(C) at distances from 50m to 300m, and varied little if at all with distance. To the left of the gun, the peak sound pressure level of 161dB(C) at 0.3m reduced to 128dB(C) at 32m. The peak sound pressure level was estimated to be 137dB(C) at a distance of approximately 20m to the left-hand side. Hearing protection must therefore be worn by anyone closer than 20m to a person firing. The peak sound pressure level was estimated to be 135dB(C) at a distance of approximately 25m and therefore hearing protection is recommended at distances of up to 25m. The sound exposure level of 98dB(A) at 20m indicated that an observer at this distance could hear about 1440 rounds without hearing protection before the noise exposure reached the upper exposure action value specified in the Control of Noise at Work Regulations 2005. Peak sound pressure levels were on average 2.4dB higher at the left ear compared with the right ear.

Measuring the Risk of Impulsive Noise at Work: One Practitioner’s Tips

There is a risk of immediate damage to hearing from short duration, high-level impulsive sounds that are typically perceived as “bangs”. These sounds may arise from impact action tools, weaponry, and explosive events. The risk is normally associated with the instantaneous peak sound pressure level. Reliable measurement of these high-peak sound pressure levels can be challenging, particularly when special low-sensitivity microphones or transducers are required. It is also important that the health and safety practitioner is aware of the limitations of their instrumentation and the limitations of various types of measurement and analysis when sound is impulsive. Included here are tips from the author’s practical experience of testing the performance of noise measurement instrumentation and hearing protection in impulsive noise, and notes of standard methods to estimate the attenuation provided by hearing protection.

Avoidance of Pile-Driving Noise by Hudson River Sturgeon During Construction of the New NY Bridge at Tappan Zee.

Sturgeon movements were monitored during a pile-driving operation. Fewer sturgeon were detected during pile driving and remained for a shorter time than during silent control periods. Moreover, the short time spent by sturgeon near pile driving suggests that they were unlikely to have reached the criterion of 187 dB re 1 μPa(2)·s cumulative sound exposure level. These results suggest that sturgeon are likely to avoid impact pile driving and not remain long enough to experience physiological effects, thus providing empirical evidence that the 206 dB re 1 μPa peak sound pressure level is the appropriate criterion for assessing the impacts of pile-driving noise on sturgeon.

Occupational noise exposure on a Royal Navy warship during weapon fire.

Introduction:Measurements were made of the sound pressure levels on a military ship HMS Grimsby during firing of a Heavy Machine Gun (HMG) mounted on the starboard bridge wing. The measurement positions comprised three locations on the ship's bridge (the wheelhouse) and one location on the starboard bridge wing.Equipment and Procedure:The three locations on the bridge were the starboard door, centre and port door. A total of 255 burst firings were measured during the survey comprising 850 rounds with each burst encompassing from 1 to 10 rounds.Analysis:The data have been assessed and interpreted in accordance with the Control of Noise at Work Regulations 2005.Results:The highest peak sound pressure levels measured on the bridge wing and on the bridge were 160.7 dB(C) (2170 Pa) and 122.7 dB(C) (27.3 Pa), respectively. The highest sound exposure levels measured on the bridge wing and on the bridge corresponding to one round being fired were 127.8 dB(A) and 88.9 dB(A), respectively. The ship's structure provided about 40 dB attenuation in the transmitted noise.Discussion:The operator of the weapon would be required to wear some form of hearing protection. On the basis of the measured peak noise levels, there would be no requirement for bridge crew to wear any hearing protection during firing of a HMG. However, crew exposure to noise on the bridge is likely to exceed the upper exposure action value corresponding to 85 dB(A) after about 11,750 rounds.Conclusions:Measurements made on the bridge wings are likely to be affected by reflections from the ship's structure.

A Change in the Use of Regulatory Criteria for Assessing Potential Impacts of Sound on Fishes.

The National Marine Fisheries Service (NMFS) currently uses interim criteria developed on the US West Coast to assess the potential onset of peak and cumulative effects of noise on fishes. Analyses performed for this project provided adequate support for the NMFS to use the peak criterion (i.e., area ensonified by 206 dB re 1 μPa peak sound pressure level [SPL(peak)]) for estimating the incidental take of Hudson River sturgeon. Application of the peak criterion (rather than the cumulative criterion) could have implications for future construction projects because estimates of take using SPL(peak) will generally be considerably lower than estimates of take based on the cumulative sound exposure level.

Development and validation of a new adaptive weighting for auditory risk assessment of complex noise

Noise-induced hearing loss (NIHL) still remains as a serious occupational related health problem worldwide. A-weighted equivalent sound pressure level (SPL) LAeq has been widely used to assess the auditory risk of occupational noises in noise measurements standards. In addition, C-weighting is also used in the standards for detection of peak SPL of noise. However, both A-weighting and C-weighting have limitations on evaluation of high-level complex noise, which is often experienced in many military and industrial fields. In this study, we proposed a new adaptive weighting (F-weighting) for more accurate evaluation of complex noises. F-weighting is based on the blending of A-weighting and C-weighting through the weighting coefficients αA,T and αC,T. To determine αA,T and αC,T, two parameters, kurtosis (KT) and oscillation coefficient (OT) were introduced. Complex noise exposures in animal studies and noise signals measured in a mining facility were applied to validate the performance of F-weighting. The results show that F-weighting performs better than both A-weighting and C-weighting on the assessment of high-level complex noise. In addition, F-weighting based LFeq shows higher correlation with the hearing loss of the animal experimental data compared with A-weighted LAeq, C-weighted LCeq, and Non-weighted Leq. The proposed F-weighting could be a potential alternative weighting for the assessment of high-level complex noise in military and industrial applications.

The effect of seismic waterguns on the inner ears of round goby

Abstract High-pressure acoustic sources, such as seismic exploration technology or sonar, can temporarily or permanently affect the auditory system of some fish species. The majority of studies done on fish hearing aim to determine safe acoustic operating thresholds for different fishes in order to mitigate possible negative effects of these anthropogenic noise sources. In contrast, the present study was designed to evaluate the effects of a hydraulic watergun on invasive round goby in Lake Michigan as a potential population suppression tool to protect critical spawning habitat for native fishes. The goal of the present study was to evaluate the potential sub-lethal effects of pulse pressure sound technology on the hearing end organs of round goby. Round goby from Little Traverse Bay near Charlevoix, MI were exposed to 6 discharges from a seismic watergun at an average peak sound pressure level of 229 dB re 1 μPa. Fish were monitored for 60 h post-exposure and assessed for damage to otoliths and inner ear sensory hair cells. We found no significant hair cell loss or otolith damage, suggesting that a higher peak pressure level or longer duration of discharges are needed to cause significant damage to round goby inner ear anatomy.

Evaluation of high-level noise exposures for non-military personnel

Noise-induced hearing loss is often attributed to exposure to high-level impulsive noise exposures from weapons. However, many workers in industries such as mining, construction, manufacturing, and services are exposed to high-level impulsive noise. For instance, construction workers use pneumatic tools such as framing nailers that can produce impulses at levels of 130 dB peak sound pressure level or greater. Miners have exposures to roof bolters and jack-leg drills that produce more of a continuous, but highly impulsive noise. In some areas of manufacturing the exposures include drop forge processes which can create impacts of more than 140 dB. Finally, in the services sector, law enforcement personnel who maintain proficiency with firearms experience the full gamut of small-caliber firearms during training. This paper will examine the noise exposures from recordings that the NIOSH Hearing Loss Prevention Team have collected. The noises will be evaluated with different damage risk criteria for continuous and impulse noise where appropriate.

An investigation of light and sound levels on intensive care units in China

BackgroundThe intensive care units’ (ICU) environment is considered clinically relevant sources of stress for patients. ObjectivesTo measure 24-h sound and light levels in 7 ICUs in China [four medical (MICU), two surgical (SICU) and one coronary (CCU) ICUs] and to identify the main sources related to increased sound levels. MethodsSound pressure and light levels were monitored for specific times over a 24-h period using a digital sound level meter and a light detector in 7 ICUs. Sound pressure levels were measured for 20min every hour. The main events at the time of peak noise levels were recorded. Light levels were measured every 2h at three locations for each ICU: near a window, in the centre of the room, at eye level of a patient receiving assisted ventilation. ResultsThe mean value of 24-h sound pressure levels exceeded 50dB(A) in all ICUs, ranging from 56.5 to 70.1dB(A). The SICUs and CCU had higher sound pressure readings from 0700h to 1600h, compared to the MICUs where the sound pressure readings reflected less variability across the 24-h period. Marked differences were observed in luminance levels among various ICUs and also across the 24-h period for all three locations. The mean highest level of nocturnal luminance at eye level of patients receiving assisted ventilation ranged from 15 to 489lx before midnight (1800–2400h) and 10 to 239lx after midnight (2401–0759h). ConclusionsHigh sound pressure levels are prevalent throughout 24h in the ICUs, especially in the SICU. Many of the readings exceeded international standards. Peak sound pressure levels were related primarily to staff activities and the alarm sounds of machines. ICU patients are exposed to high levels of artificial light continuously throughout the day and night.