Sound Pressure Level Difference Research Articles

Basic examinations of the sound transmission loss measurement using two cardioid microphones

This paper reports results of an experiment on sound transmission loss measurement using the C-C method. This method is an inexpensive and stable method for measuring the sound pressure, the particle velocity, and the sound intensity. The measurements are carried out in accordance with JIS A 1441-1:2007 based on ISO 15186-1:2000, and the C-C method is applied for measuring the sound intensity. Comparing the measured results with those of the sound pressure level difference method, comparable results are obtained above 250 Hz. Naturally, the precision of the measurements depends on the microphone calibration used in the C-C method. In this report, we employ two calibration methods using an acoustic tube and an anechoic chamber, and also exhibit comparison of the results obtained by these methods.

Reflection function, reflectance, and area function measurements in ears of children and adults.

The main experiment concerned time-domain measurements of the acoustical reflection function (RF) of the human ear in adults and children (aged 5 to 8 years) using a probe inserted into the ear canal. This RF was used to calculate the area function of the ear canal versus distance along its centerline. Acoustical reflectance was calculated in the frequency domain from the RF, as was the difference in sound pressure level near the tympanic membrane relative to the probe tip. Group responses in area function, total ear-canal length, absorbance and group delay, and admittance magnitude and phase were analyzed based on sex, ear, and age. Responses were compared between children/adults and younger/older adults relative to age 50 years. Ear and sex were never significant. Significant differences were observed in children compared to adults in the area function, absorbance and group delay, and admittance magnitude and phase (0.25-4 kHz). Group delay differed between younger and older adults. A second experiment assessed level dependence of responses to better understand limitations in probe performance observed in the main experiment. These results show the utility of time-domain measurements of the area function and derived reflectance to understand sound-transmission differences across age at frequencies important to middle-ear function.

Incorporation of Silicone Mold Residues Influence on Acoustic Properties of Subfloor Mortars

The determination of minimum performance criteria for residential buildings has encouraged the development of new technologies by companies linked to the construction industry. In this context, the acoustic performance of floor systems is of great importance. One of the solutions to improve the performance of these systems is the incorporation of lightweight aggregates to replace natural fine aggregates in the subfloor mortars, with the aim of attenuating the noise caused by impact, thus improving acoustic performance. Therefore, the objective of this study was to analyze the properties of a subfloor mortar in a 1:4 ratio (cement:sand), with the incorporation of silicone mold residue, replacing natural fine aggregate, in proportions of 10%, 20%, and 30%. %, and a water/cement ratio (w/c) of 0.93. Tests were performed in the fresh and hardened state, such as incorporated air content, mass density, consistency index, flexural tensile strength, compressive strength, water absorption by capillarity, in addition to a specific test to determine the difference in sound pressure level between specimens. The results indicated that the mortar consistency was influenced by the incorporation of waste, increasing with its incorporation. The increase in consistency positively influenced the mechanical resistance of the mortars, which showed an increase with higher residue content, due to the reduction in the amount of voids. Consequently, densities also increased with high waste content. The acoustic test showed satisfactory results, with good attenuation of 10%, indicating an 8 dB improvement in the sound pressure level. The results presented show that the residue has great potential for acoustic attenuation.

Analysis of blade noise with different root boundary conditions considering fluid-structure interaction effect

It is of certain importance for noise reduction to investigate the relationship between the aeroacoustic characteristics of blade and root boundary conditions when considering the fluid-structure interaction (FSI) effect. In this study, a set of precise dynamic models and two-way FSI calculation methods are developed to predict the dynamic load and response of blades more accurately. The natural frequency inaccuracy of the blade model is kept within 5% by comparing the results of the modal test using the ploy-reference time domain method and adopting the sensitivity analysis method with the blade beam stiffness as the modification parameter. Besides, based on the numerical results from the computational fluid dynamics method considering the FSI effect, the aeroacoustic characteristics of blades with different root boundary conditions are analyzed by adopting the Ffowcs Williams-Hawkings equations. The aeroacoustic characteristics of the NACA blade in hover are thoroughly discussed, with emphasis on the impact of different root boundary conditions on rotation noise. The result demonstrates that, the sound pressure level (SPL) difference of loading noise can reach 1.4 dB between blades with various root boundary conditions, while the SPL difference of thickness is only 0.4 dB.

The Use of Waste Tyre Rubber Recycled Products in Lightweight Timber Frame Systems as Acoustic Insulation: A Comparative Analysis of Acoustic Performance

The current European standards demand more energy-efficient, comfortable, and sustainable buildings and encourage the incorporation of recycled materials in building construction. Timber buildings are successfully competing with traditional building materials in addressing these challenges; however, one of the weaknesses of timber systems is their limited sound insulation capacity. One material that can fit into the sustainability aims of timber construction and improve its acoustic performance is recycled ground tyre rubber (GTR), which, on top of this, is a serious environmental problem. This paper presents research on the use of GTR materials combined with timber systems in order to improve their acoustic performance. Three different types of GTR products (granulate, rolls, and sheets) of different thicknesses and densities are selected and are combined with different sound-absorbing materials (mineral wool, cellulose, and wood fibre) inside a lightweight timber sandwich system. In this study, the first qualitative approach, the acoustic performance of the different resulting systems is compared based on the sound pressure level difference measured in a custom-made reduced-size transmission chamber. Secondly, the sound reduction index of four selected specimens is measured in an accredited sound transmission laboratory. The results show that, for all the lightweight timber systems included in this research, introducing a GTR layer improves the acoustic performance of the system.

Field acoustical measurements for sound insulation residences against aircraft noise

In this paper, we have investigated measurement methods of the sound insulation performance for residences treated with increased sound insulation near airports in Japan. The flyover measurement method and the loudspeaker measurement method are conducted to verify the performance. The first one provides the performance of the whole facades of a house using aircraft noise, approximately similar to the FAA method described in ASTM E966. The pressure level outdoors is measured at enough high position to ignore the interference with sound from the ground or the house roof. However, the microphone is sometimes put on the roof surface because of being in the house's shadow in the overcrowded residential area. Thus, we have investigated the sound pressure level difference between the high and surface positions using simple numerical analysis and field measurement. On the other hand, the outdoor and indoor loudspeaker methods are conducted for facade elements such as windows and doors, according to JIS A 1520. The sound insulation performance for facade walls is also measured with ISO 16283-3; however, the loudspeaker sometimes cannot be positioned far enough from the wall. Thus, we have proposed the measuring method for the facade wall by applying the indoor loudspeaker method.

High level sound transmission through cadaver human ears—On the influence of bone conduction and hearing protective devices

High level sound exposure can cause substantial injury to the auditory system, motivating efforts to predict and prevent this injury. Measurement techniques using acoustic manikins are effective for low and moderate sound levels, but nonlinear effects in the middle ear and alternate sound transmission pathways to the inner ear limit their utility at higher sound pressure levels. Here, we describe results from a series of measurements made in cadaveric human ears conducted in our laboratory over the last several years. We quantified sound transmission to the inner ear by measuring the difference in sound pressure level across the cochlear partition near the base of the cochlea, which drives basilar membrane motion. We describe measurements quantifying sound transmission through the human middle ear, which is limited by suspensory ligaments for sounds above approximately 130 dB SPL, resulting in nonlinear (harmonic) distortion of sounds in the cochlea at higher sound pressure levels. Similarly, we describe observations of sound transmission to the cochlea via bone conduction from vibratory transducers, as well as high level sound and impulse noise/blast exposures. The implications of these measurements for hearing loss predictions, effectiveness of hearing protective devices, and injury mechanisms are discussed.

Glass Microspheres Thermo-Deformation Sintering Processes in the Technologies of Obtaining Materials for Underwater Technical Equipment

Abstract In this work, the important scientific and technical problem of creating multifunctional composite materials for shipbuilding and ocean engineering was solved. The work aimed to study the thermal deformation processes of sintering glass microspheres to obtain lightweight glass composites with a cellular structure that provides positive buoyancy and sound insulation properties. For this purpose, glass microspheres of Na2O‒SiO2 and Na2O‒B2O3‒SiO2 composition with a dispersion of 10 to 60 μm were used as raw materials. They were sintered to form a closed, porous structure. The theoretical substantiation of technological parameters is based on the concepts of solid state and glassy state chemistry and physicochemical concepts of glass softening processes. The process of hot-pressing glass microspheres without plasticisers and additives was investigated. The author’s own laboratory equipment was used for the experiments. The sintering intensity was determined from the results of shrinkage processes; the kinetic shrinkage curves were constructed in semilogarithmic coordinates. The glass composite samples were examined by optical and electron microscopy. As a criterion, the storage of spherical microspheres under the influence of simultaneous heating to 700 °C with the application of pressure in the range of 0,5 to 1,5 MPa was chosen. It was established that the formation of a predominantly closed-porous structure of glass composites with a density of 350...600 kg/m3 occurs by the mechanisms of viscous glass phase flow through liquefaction processes in the walls of microspheres. At the same time, shrinkage processes in the linear direction reach up to 50%. The acoustic properties were investigated by measuring the differences in sound pressure levels in octave frequency bands using a Kundt pipe. The water absorption of the glass composite samples was determined at hydrostatic pressures up to 20 MPa. The research results were compared with the characteristics of analogue composites, such as syntactic foams and foam glass. The developed materials can be used in the design and manufacture of technical equipment for research and maintenance of underwater infrastructure. The prospects for further research are related to the feasibility study and marketing research on implementing the developed glass composites.

Auditory environment diversity quantified using entropy from real-world hearing aid data.

Using data collected from hearing aid users' own hearing aids could improve the customization of hearing aid processing for different users based on the auditory environments they encounter in daily life. Prior studies characterizing hearing aid users' auditory environments have focused on mean sound pressure levels and proportions of environments based on classifications. In this study, we extend these approaches by introducing entropy to quantify the diversity of auditory environments hearing aid users encounter. Participants from 4 groups (younger listeners with normal hearing and older listeners with hearing loss from an urban or rural area) wore research hearing aids and completed ecological momentary assessments on a smartphone for 1 week. The smartphone was programmed to sample the processing state (input sound pressure level and environment classification) of the hearing aids every 10 min and deliver an ecological momentary assessment every 40 min. Entropy values for sound pressure levels, environment classifications, and ecological momentary assessment responses were calculated for each participant to quantify the diversity of auditory environments encountered over the course of the week. Entropy values between groups were compared. Group differences in entropy were compared to prior work reporting differences in mean sound pressure levels and proportions of environment classifications. Group differences in entropy measured objectively from the hearing aid data were also compared to differences in entropy measured from the self-report ecological momentary assessment data. Auditory environment diversity, quantified using entropy from the hearing aid data, was significantly higher for younger listeners than older listeners. Entropy measured using ecological momentary assessment was also significantly higher for younger listeners than older listeners. Using entropy, we show that younger listeners experience a greater diversity of auditory environments than older listeners. Alignment of group entropy differences with differences in sound pressure levels and hearing aid feature activation previously reported, along with alignment with ecological momentary response entropy, suggests that entropy is a valid and useful metric. We conclude that entropy is a simple and intuitive way to measure auditory environment diversity using hearing aid data.

Phonetic features of patients with transoral endoscopic thyroidectomy

The objective of this study was to compare phonetic outcomes of TOETVA with those of conventional transcervical thyroidectomy(OPEN). Retrospective chart review of total 61 patients who received thyroidectomy through OPEN (n=34) or TOETVA (n=27) approach in single tertiary center were enrolled. There were significant differences in F0 between the two groups and there were significant changes from different time points within each group in jitter for vowel /i/. Aerodynamically, there were significant differences in mean sound pressure level for vowel /a/ and mean sound pressure level, mean air pressure, and aerodynamic resistance for syllable /pa/ between the two groups. In subjective VHI evaluations, there were no significant differences between the two groups. This study is significant in that it has investigated voices of patients with TOETVA. Results of this study are expected to be useful for voice evaluation, treatment, and prevention in the future.

The effect of furniture when measuring reverberation times at low frequencies from 31.5 Hz

When evaluating impact sound insulation of dwellings, including frequencies below 50 Hz has been reported to improve the correlation between the measurements and the occupants’ rating of annoyance from footstep noise. To determine the impact sound insulation, the reverberation time of the receiving room must be considered, a procedure that may introduce large errors at low frequencies. If it can be shown that normal furniture does not affect the absorption (and thereby neither the reverberation time), the reverberation time below 50 Hz could be omitted in the evaluation of impact sound insulation. This would improve the measurement accuracy of the impact sound insulation and simplify the measurement procedure. The purpose of this paper is to investigate to what extent fully furnished rooms for residential purposes affect the reverberation time. Measurements are conducted using the integrated impulse response method in two empty and furnished bedrooms of different construction. Due to the potential errors in the reverberation time measurement, sound pressure level was measured for comparison. No statistically significant absorption difference due to furniture could be found at frequencies below 50 Hz, neither for the measured reverberation times nor the difference in sound pressure level. As a consequence, impact sound insulation may be evaluated without any reverberation measurement below 50 Hz.

Dependence of binaural gain for infrasound on interaural phase difference.

Increasing complaints about infrasound have generated interest in understanding its perception, including binaural effects. This study investigated the level difference between monaural and binaural presentation required for detection and equal loudness (binaural gain) for pure tones with frequencies of 8, 32, and 400 Hz and an 8 Hz sinusoidally amplitude-modulated tone with diotic 400 Hz carrier. Monaural stimuli were compared to binaural stimuli with interaural phase differences (IPDs) of 0°, 90°, and 180° in two experiments: absolute threshold measurements and loudness matching at 40 phons. The latter was repeated with transposed tones (400 Hz carrier multiplied by a half-wave-rectified 8 Hz sinusoid). When expressed as differences in sound pressure level, similar binaural gain was found across all stimulus types under the diotic condition. Confirming previous studies, the gain was larger at supra-threshold levels (40 phons) than at threshold. However, when the loudness-matching results were expressed as binaural gain with respect to the loudness level, they became 17.5, 11.2, and 5.8 phons for the 8, 32, and 400 Hz stimuli, respectively. Results for the 8 Hz pure tone and the transposed stimulus were IPD dependent.

Conductor Identification Using Acoustic Signal Method

Electrotechnical services spend a significant amount of time on cable tracing and conductor identification operations. Although the operation of conductor identification seems an easy job and a deeply researched topic, it may turn out to be time-consuming due to the large quantity of unidentified conductors (cables) and the certain stipulation that conductors should be de-energized and have uninsulated parts. This paper proposes a method based on the use of an acoustic signal as a carrier, making it possible to facilitate the identification process and significantly speed up the identification process. For the proposed method, mathematical modeling of the sound propagation in conductors and insulation is detailed. The sound pressure level subject to identified conductor length, conductor cross-section and insulation type was calculated on the basis of the model. The performed calculations revealed remarkable capabilities of the acoustic method for identifying conductors in comparison with other methods. So, the difference in sound pressure level is only 3.65% for distances from the identification point to the signal source of 5 m and 100 m, 0.42% between the minimum and maximum cross sections of conductors (1 mm2 and 25 mm2, respectively) and 0.22% between conductors with polyethylene and PVC insulations. The prototype of conductor identification device was assembled in a way that practically confirmed the theoretical research with the average percentage of discrepancy of about 1.44%. In addition, the paper analyzes the conductor identification operation constituents to justify the application of the acoustic method by comparison with other identification methods.

Study on prediction in far-field aerodynamic noise of long-marshalling high-speed train.

It is still difficult to conduct numerical calculation of the aerodynamic noise of full-scale, long-marshalling, high-speed trains. Based on the Lighthill acoustic analogy theory, the aerodynamic sound source of the high-speed train is equivalent to countless micro-vibrating sound sources. An acoustic radiation model of the dipole sound source of high-speed trains is established, and a method to predict the aerodynamic noise in the far field of long-marshalling high-speed trains is proposed. By this method, combined with numerical simulation technology, the flow field, noise source, and far-field noise characteristics of high-speed trains with different marshalling numbers are studied. The improved delayed detached eddy simulation method is used for flow field calculation, to obtain aerodynamic noise source information regarding the surface of high-speed trains. The numerical calculation method is verified by wind tunnel testing. The results show that the flow field and noise source characteristics of high-speed trains with different marshalling numbers are similar. The greater the length of the train body, the longer the trailing distance of the train wake, and the stronger of a surface noise source the tail car becomes. The spatial distribution characteristics of aerodynamic noise in the far field of high-speed trains do not change significantly with the length of the train body, but the magnitude of the sound pressure level will increase with the increase in length of the train body. The middle car body parts of high-speed trains with different marshalling numbers have similar noise distributions and sound pressure levels. Based on the noise calculation results of the 3-marshalling high-speed train, the far-field noise of the 5-marshalling and 8-marshalling train models is predicted and found to be in good agreement with the far-field noise of the actual train model. The differences in average sound pressure level are 1.01 dBA and 1.74 dBA, respectively.

A comparison of noise produced by blank and live rounds fired from military rifles

The difference in sound pressure levels between blank and live rounds fired from military rifles has been investigated. The rifles tested were a Colt Canada C8 carbine rifle, a Lewis Machine LM7 sharpshooter, and a SA80 individual assault rifle. Sound pressure waveforms were measured approximately 15 cm away from the right ear of the operator standing on a hard concrete surface. Twelve blank rounds and twelve live rounds were fired from each weapon during the survey: a total of 72 rounds. The twelve repeat rounds showed a maximum difference of 3.4 dB between peak sound pressure levels for blank rounds fired from the Colt C8 rifle. The highest peak sound pressure of 160 dB(C) was measured for a live round from the C8 rifle. The mean peak sound pressure levels for the C8, LM7 and the SA80 were 154.0 dB(C), 153.1 dB(C) and 147.0 dB(C), respectively, for blank rounds, compared with 159.0 dB(C), 154.8 dB(C) and 152.7 dB(C), respectively for live rounds. This shows that, significantly higher sound pressure levels occurred when firing live rounds compared with blank rounds. Similar differences were measured in sound exposure levels for the rounds fired from the three weapons. The data can be used to determine the main frequency range present in the sound pressure waveforms for the three weapons for assessing the suitability of appropriate hearing protectors.

Just noticeable difference of sound pressure level of speech in open-plan office

In this study, the general sound environment characteristics of open-plan office (OPO) were investigated, and just noticeable difference (JND) of sound pressure level of speech at a distance of 4 m (Lp,A,S,4m) suggested in ISO 3382-3 was suggested. First, in order to understand the sound environment characteristics of OPO, one minute sound sources recorded in 8 offices were collected and physical and psychological acoustic characteristics were analyzed. A total of 30 office workers were subject to subjective evaluation on 8 sound sources, and they were asked to respond to questionnaires related to annoyance, work satisfaction, and speech privacy. Next, to investigate the JND, two computer simulation models identical to those of the actual OPO were implemented, and sound sources each having six different Lp,A,S,4m values were generated through the change of the sound absorption coefficient of the interior finish. The JND of Lp,A,S,4m was presented by performing paired comparison for the same subjects. It is expected that the JND of Lp,A,S,4m proposed in this study can be used for the sound environment rating of OPO.

Acoustical role of ear canal in exposure to the typical occupational noise levels.

Background: Exposure to noise associated with injuries has become a public health issue in recent years. This study aimed to show the role of the acoustical structure of the ear canal on the typical occupational sound pressure levels at different frequencies. Methods: This cross-sectional study was done on 20-30-year-old participants. White noise was used at 3 levels, including 75, 85, and 95 dB as the stimulus sound pressure levels (SSPLs). The speakers had a 1.5-meter distance from the participants and at the height of 87 centimeters from the lab ground and were located in front of the participants. The SSPLs were measured outside (cavum part of the external ear) and inside the right ear of each participant. Measurements were done at the total sound pressure level and in the 1/1 octave frequencies. The duration for each measurement was 10 seconds. The independent sample t test was used for the statistical analysis, and the equality of means were rejected at p<0.05. Results: There were 30 (50%) males out of the 60 participants. The mean ± SD for the age of all the participants was 23.29±2.93 years. The total sound pressure level difference between the inside and outside of the ears of male and female participants was statistically significant (p<0.001) at the stimulus sound pressure levels. The peak resonance was observed in the frequencies 2000 Hz and 8000 Hz for males and 8000 Hz for females. Conclusion: The ear canal can amplify the sounds and increase the sound pressure levels. This amplification was found to be greater for males than for females.

Ambient noise exposure induces long-term adaptations in adult brainstem neurons

To counterbalance long-term environmental changes, neuronal circuits adapt the processing of sensory information. In the auditory system, ongoing background noise drives long-lasting adaptive mechanism in binaural coincidence detector neurons in the superior olive. However, the compensatory cellular mechanisms of the binaural neurons in the medial superior olive (MSO) to long-term background changes are unexplored. Here we investigated the cellular properties of MSO neurons during long-lasting adaptations induced by moderate omnidirectional noise exposure. After noise exposure, the input resistance of MSO neurons of mature Mongolian gerbils was reduced, likely due to an upregulation of hyperpolarisation-activated cation and low voltage-activated potassium currents. Functionally, the long-lasting adaptations increased the action potential current threshold and facilitated high frequency output generation. Noise exposure accelerated the occurrence of spontaneous postsynaptic currents. Together, our data suggest that cellular adaptations in coincidence detector neurons of the MSO to continuous noise exposure likely increase the sensitivity to differences in sound pressure levels.

Effects of task and language nativeness on the Lombard effect and on its onset and offset timing.

This study focuses on the differences in speech sound pressure levels (here, called speech loudness) of Lombard speech (i.e., speech produced in the presence of an energetic masker) associated with different tasks and language nativeness. Vocalizations were produced by native speakers of Japanese with normal hearing and limited English proficiency while performing four tasks: dialog, a competitive game (both communicative), soliloquy, and text passage reading (noncommunicative). Relative to the native language (L1), larger loudness increments were observed in the game and text reading when performed in the second language (L2). Communicative tasks yielded louder vocalizations and larger increments of speech loudness than did noncommunicative tasks regardless of the spoken language. The period in which speakers increased their loudness after the onset of the masker was about fourfold longer than the time in which they decreased their loudness after the offset of the masker. Results suggest that when relying on acoustic signals, speakers use similar vocalization strategies in L1 and L2, and these depend on the complexity of the task, the need for accurate pronunciation, and the presence of a listener. Results also suggest that speakers use different strategies depending on the onset or offset of an energetic masker.

Anomalous Noise Measurement and Analysis of the Valve Hall in ±800kV UHV Converter Station

In order to control the anomalous noise of the pole-I valve hall in a ±800kV UHV converter station, the background noise of the valve hall and the noise of each valve group in the valve tower are measured, respectively. The sound pressure level differences of the valve groups are compared. The anomalous noise locates in the short-circuit pipe of cooling water in the valve tower. Frequency spectrum analysis shows that the abnormal noise is related with the flow of cooling water. The two-dimensional finite element model is established to analyze the influence of chamfer angle and pipe length on the flow velocity of cooling water. The result shows that the abnormal noise is only related with the chamfer angle of the short-circuit pipe with constant flow velocity. The abnormal noise is successfully controlled by structure improvement of the short-circuit pipe and the potential risk to the valve group is avoided, which will give technique support to the operation and maintenance of the valve hall in UHV converter stations.