Sound Level Difference Research Articles

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.

Determining the dynamics of electromagnetic fields, air ionization, low-frequency sound and their normalization in premises for computer equipment

This paper reports a study into the quantitative values and dynamics of physical factors in premises and workplaces of stationary and portable computers. The factors that are practically not perceived by the senses of operators were investigated. It is established that modern monitors do not generate electromagnetic fields of hygienically significant levels. System units generate electric fields (18‒22 V/m) and magnetic fields (220‒245 nT) that are approaching the maximum permissible. Sources of uninterruptible power supply and fluorescent lighting systems generate excess magnetic fields (up to 2250 nT and 2300 nT), respectively. The main excessive factor for portable computers is electric fields (up to 9 kV/m), which is the cause of air deionization in the user's zone of stay. It is shown that one system unit in the normative volume of the room (20 m3) deionizes air (into 100 cm-3 positive and 200 cm-3 negative). The generation of ions by modernized laser printers and photocopiers of various models (up to 1500 cm-3 and 2800 cm-3, respectively) was investigated. The distances at which the ionic composition of the air corresponds to the background values (1.0‒1.5 m) were determined. That requires the introduction of artificial air ionization in workplaces of users and a decrease in the levels of electrostatic fields. The spectral composition and amplitudes of magnetic fields of external power supplies of laptop computers were determined. It is shown that the difference in sound levels measured on the scales "Lin" and "A" reaches 24 dB, which indicates a significant impact of infrasound on users. Membrane-type protective panels configured for maximum resonant frequencies of low-frequency sound and infrasound have been proposed

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.

Designing Urban Soundscape for Various Activities based on Soundscape Expectation

The concept of soundscape aims to provide a more holistic understanding of the acoustic environment by taking several aspects into account, such as human perception, the acoustic environment and the context of the space. The soundscape concept is primarily concerned with the human experience and is considered more effective to access the acoustic quality of urban areas than traditional sound measurement. Soundscape analysis was used in this study to determine the relationship between various activities occurring in urban areas and their associated sound sources. This relationship can be used as design guidance for urban soundscape. The interaction was analyzed using the soundscape expectation approach, which is based on people’s memories of urban areas. The participants of this study were requested to compose an ideal acoustic environment according to their expectation for doing four activities: reading, relaxing, talking with friends, and playing with children. According to the data of the participants’ composition there is no significant difference in the overall sound levels between various activities. As a result, the appropriate acoustic environment cannot be determined solely based on the overall sound level. Individuals have varying expectations of sound sources when engaging in various activities.

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.

S-shaped dependence of the sound pressure level in outdoor propagation on the effective sound speed gradient

The effective sound speed gradient is used to describe the meteorological conditions during sound measurements at roads and railways. Meteorological parameters were assessed up to a height of 10 m. The sound level differences between a reference point close to the passing vehicles and at distances of 100–500 m from motorways and railway tracks were determined. These differences were found to correlate well with the effective sound speed gradient determined from the measured temperature and wind speed gradients which follow the day/night cycle as a result of the reversing air temperature gradient, incoming solar radiation and wind conditions. The correlation with sound level differences can be approximated by an S-shaped function which is constant for large positive or negative gradients of the effective sound speed. These threshold values are a consequence of the local meteorological and attenuation conditions. The analysis shows that large effective sound speed gradients are mainly a result of the wind conditions whereas gradients without a substantial wind speed contribution are low and a result of the temperature gradient. In the distance range between 150 m and 250 m, the meteorological influences cause a level increase of 3–4 dB(A) for downward refracted sound rays (favourable sound propagation) compared to a situation without meteorological influence (effective sound speed gradient of zero). In the same distance range, meteorological conditions cause a maximum sound level attenuation of 5–10 dB(A) for upward curved sound rays (unfavourable sound propagation).

Listening in the Mix: Lead Vocals Robustly Attract Auditory Attention in Popular Music

Listeners can attend to and track instruments or singing voices in complex musical mixtures, even though the acoustical energy of sounds from individual instruments may overlap in time and frequency. In popular music, lead vocals are often accompanied by sound mixtures from a variety of instruments, such as drums, bass, keyboards, and guitars. However, little is known about how the perceptual organization of such musical scenes is affected by selective attention, and which acoustic features play the most important role. To investigate these questions, we explored the role of auditory attention in a realistic musical scenario. We conducted three online experiments in which participants detected single cued instruments or voices in multi-track musical mixtures. Stimuli consisted of 2-s multi-track excerpts of popular music. In one condition, the target cue preceded the mixture, allowing listeners to selectively attend to the target. In another condition, the target was presented after the mixture, requiring a more “global” mode of listening. Performance differences between these two conditions were interpreted as effects of selective attention. In Experiment 1, results showed that detection performance was generally dependent on the target’s instrument category, but listeners were more accurate when the target was presented prior to the mixture rather than the opposite. Lead vocals appeared to be nearly unaffected by this change in presentation order and achieved the highest accuracy compared with the other instruments, which suggested a particular salience of vocal signals in musical mixtures. In Experiment 2, filtering was used to avoid potential spectral masking of target sounds. Although detection accuracy increased for all instruments, a similar pattern of results was observed regarding the instrument-specific differences between presentation orders. In Experiment 3, adjusting the sound level differences between the targets reduced the effect of presentation order, but did not affect the differences between instruments. While both acoustic manipulations facilitated the detection of targets, vocal signals remained particularly salient, which suggest that the manipulated features did not contribute to vocal salience. These findings demonstrate that lead vocals serve as robust attractor points of auditory attention regardless of the manipulation of low-level acoustical cues.

Firework activity and environmental sound levels: community impacts and solutions

ABSTRACT We conducted a comprehensive urban sound and community noise perception assessment, using the lens of illegal firework activity during the unique social climate of 2020 as its motivation. Using data gathered from stationary monitoring sites, our research app NoiseScore, emergency (911) and non-emergency (311) phone call reports, and data from the United States Census we observed significant neighborhood differences in sound levels associated with firework activity. We observed that firework activity was dominated by low-frequency sound across all neighborhoods. This trend persisted by time of day and day of week. Further, it was low-frequency sound ranges (and alternative weighting systems like C-weighting and Z-weighting that penalized lower frequency sound levels less) that had the highest correlations with 911 and 311 firework calls. Keywords qualitatively examined from 311 data like ‘bomb’, ‘explosion’, ‘PTSD’ and ‘war zone’ highlight that many residents associate the detonation of fireworks to danger, and view fireworks as an environmental psychological trigger that for many residents – particularly veterans, those living in neighborhoods impacted by gun violence, or victims of gun violence – is quite traumatic. Comparing our findings to existing epidemiological studies suggest that incessant firework activity puts residents at risk for negative cardiovascular and mental health outcomes.

The Restorativeness of Outdoor Historical Sites in Urban Areas: Physical and Perceptual Correlations

Growing tourist flows, which crowd ancient city centres, have modified their liveability and threatened conservation. They have increased the need for quiet places, primarily where green parks are missing. While previous studies have highlighted the possibility of reusing hidden sites of historical buildings, it is not clear if this scheme can also be applied in other contexts, and which physical or perceptual dimensions are mainly related to the restoration of these sites. If greenery and water elements induce positive effects on people’s well-being, we want to understand if the historical–artistic component can be just as important for people’s restorativeness. To this end, the physical and perceptual characteristics of 20 different sites in Naples and Istanbul were investigated through objective and subjective surveys. The results show that the sound levels inside sites cannot consistently account for the perception of the restorativeness in Italy and Turkey, while some sound level differences caused by outside noise could. Moreover, soundscape, appreciation, maintenance/management, and importance/relevance were the main perceptual dimensions describing these places. The importance/relevance dimension was strongly correlated with all the components of the restorativeness, especially with the fascination. These findings are consistent between the Italian and Turkish groups.

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.

Influence of the COVID-19 pandemic on the external environmental noise of a public hospital in Sorocaba, Brazil

This study aimed to evaluate environmental noise around a public hospital in the city of Sorocaba, Brazil, before and during the COVID-19 pandemic. The measurements were performed in triplicate, on weekdays, at three points around the hospital during the night, and followed the guidelines of the NBR 10151/2019 standard. At the same measurement points, the manual counting of light vehicles, heavy goods, and motorcycles was performed. The equipment used was the BK 2260 analyzer and the BK 4231 calibrator. For statistical analysis, data normality was verified through the Shapiro-Wilk test and, later, the differences in sound levels before and during the pandemic through the paired t-test. The correlation between sound levels and the number of vehicles was verified by Spearman's correlation. The level of significance adopted was α=0.05. There was a significant reduction in the movement of light and heavy vehicles during the pandemic and less reduction for motorcycles. It was found that P1 was the noisiest point and the one with the lowest variation in dB(A) during the pandemic, associated with higher speed and greater circulation of vehicles. Although there is a strong correlation between the number of vehicles and sound levels, statistically there was no significant difference. It is concluded with this work that there was a reduction in environmental noise around the hospital during the pandemic and that other factors should be taken into account, such as the speed of vehicles.

Comparative Assessment of Aircraft System Noise Simulation Tools

The Aircraft Noise Simulation Working Group (ANSWr) was established by DLR, ONERA, and NASA to compare simulation tools, establish guidelines for noise prediction, and assess uncertainties associated with the simulation. A benchmark test was initiated, and initial results for a reference and a low-noise vehicle are discussed. The reference aircraft is a conventional tube-and-wing configuration with the engines installed under the wings. The low-noise variant features a high wing design with engines mounted above the wing and fuselage junction. Simulations are performed for both departure and approach conditions, and the results obtained with the different system noise prediction tools are compared. For the reference aircraft, the overall agreement is good among the three predictions. Maximum A-weighted sound pressure levels received on the ground agree within 3–4 dB. For the low-noise vehicle, the comparison of the computed results focuses mainly on the acoustic shielding calculations, as well as on the noise source components. Considering these shielding effects, all three prediction methods show remarkable good agreement, with differences in maximum A-weighted sound pressure level typically lower than 4 dB. In conclusion, the results are quite promising. Despite simulation assumptions made to assist in the comparison, this work is a first and a positive step toward the development of a reliable and comprehensive comparison of these three aircraft noise simulation tools.

Analisis Perbandingan Tingkat Tekanan Bunyi Terhadap Sistem Pembangkit Suara Akustik dengan Efek Surround dan Tanpa Efek Surround

&lt;em&gt;This study aims to determine the comparison of the sound pressure level produced by an acoustic sound generator system with surround effects without surround effects. Acoustic sound generating system with surround effects is designed and made as a sound system that produces a surround effect where the resulting sound is divided and distributed over two or many channels (multi channel). This sound system consists of four parts, namely: front cannel, rear surround channel, extra rear channel and subwoofer. This system gets input from the VCD in the form of R and L signals into the AN7397K IC then comes out through four output channels. Each output channel is connected to a 150 watt stereo and mono power amplifier. From the results of research with statistical tests using the t distribution shows that there is a difference in sound pressure level (SPL) between acoustic sound generating systems with surround effects without surround effects at a distance of 1 meter to 10 meters, where the value of the sound pressure level with a sound generator system is obtained. acoustics with a surround effect higher than the sound pressure level without a surround effect&lt;/em&gt;

Personal audio system for neckband headset with low computational complexity.

Personal audio systems have been developed based on various approaches with the goal of synthesizing an isolated sound zone that avoids disturbing others in different locations. In this work, a near-field solution for a neckband headset using three loudspeakers positioned close to each ear is proposed. In particular, it is an attempt to derive a simple multichannel filter for reducing the computational cost in mobile devices. Unlike super-directive beamforming techniques, the controlled radiation pattern is not highly directional but can boost the near-field sound, thereby providing an extra sound level difference between the listener's ear locations and far-field surrounding areas. For this purpose, a multichannel filter is designed using a conventional pressure matching technique for reproducing a target signal at the ear location while suppressing sound radiation to a far-field. It is shown that the optimal filter weights can be successfully approximated in the form of a simple broadside differential array pattern. The simplified filter structure can be realized using only two second-order infinite impulse response filters for driving the middle and two side loudspeakers. Through various simulations and experiments, it is demonstrated that the proposed solution can effectively realize a personal audio system with a minimal loss of sound isolation performance.

Articulatory activity of the tongue, jaw, and lips during the second passaggio acoustic transition of female singers

Sopranos typically exhibit an acoustic modification between 600 and 700 Hz (on /a/) during which second resonance (R2) tracking of the second harmonic (2fo) changes to first resonance (R1) tracking of the fundamental (fo). To quantify the alteration, the sound pressure level difference between the first two harmonics (L1-L2) was measured for chromatic scales sung between C5◻ and G5◻ (523 to 784 Hz) by 17 sopranos (9 judged by the first author as “techniqued” and 8 as “un-techniqued” and confirmed by perceptual experiment). Techniqued sopranos shifted from negative to positive values of L1-L2 as early as D5◻ (587 Hz), while the least techniqued singers did not make the change at all. Articulatory correlates were measured using ultrasound of the tongue and optical tracking. Head-corrected tongue contours showed the most critical articulatory factor to be the size of a triangular area between two points on the hard palate and the most anterior tongue point. Sopranos who made the change earliest exhibited the largest anterior oral cavities whereas sopranos who never made the acoustic change had significantly smaller anterior cavities. Larger anterior oral cavities appear to accommodate lower frequencies of R2, presumably lowering L2 and increasing L1-L2. [Work supported by NIH grant DC-002717.]