Sound/Noise

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TEMPORAL FLUCTUATION OF ATMOSPHERIC ABSORPTION OF SOUND AND ITS EFFECT ON AIRCRAFT NOISE PROPAGATION DURING A YEAR

TEMPORAL FLUCTUATION OF ATMOSPHERIC ABSORPTION OF SOUND AND ITS EFFECT ON AIRCRAFT NOISE PROPAGATION DURING A YEAR

1.5m above the ground of noise generated from an aircraft flying right overhead at heights from 200m to 3000m were calculated from the absorption coefficients at the range of frequency from 63Hz to 4kHz, assuming that the atmosphere is modeled by a stack of 21 horizontal layers over a range of altitude from 0 to 5000m, as mentioned in annex B, ISO 9613-1. Figure 7 shows the calculated A-weighted sound pressure levels of aircraft noise heard on the ground. It can be seen that the sound pressure levels in the winter are highly variable as compared to those in the summer, and that the mean sound pressure levels in the summer apt to be higher than those in the winter.
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6 Lee mas

Uncertainties in Environmental Noise Assessments – ISO 1996, Effects of Instrument Class and Residual Sound

Uncertainties in Environmental Noise Assessments – ISO 1996, Effects of Instrument Class and Residual Sound

ISO 1996 “Acoustics — Description, assessment and measurement of environmental noise” is currently under revision. The 2nd part, ISO/DIS 1996-2.2 “Determination of environmental noise levels” [1], contains guidelines on assessing and reporting the uncertainties of the determined sound pressure levels. This depends on the sound source and the measurement time interval, the weather conditions, the distance from the source and the measurement method and instrumentation. Some guidelines on how to estimate the measurement uncertainty are given, with focus on A-weighted equivalent-continuous sound pressure levels only. Four main sources of uncertainty (reproducibility, operating conditions, weather and ground conditions, and residual sound) are used and combined to determine the overall uncertainty (see Table 1).
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8 Lee mas

TEMPORAL VARIATION OF SOUND QUALITY UNDER LONG-TERM EXPOSURE OF CAR INTERIOR NOISE AND SEAT -FLOOR VIBRATION

TEMPORAL VARIATION OF SOUND QUALITY UNDER LONG-TERM EXPOSURE OF CAR INTERIOR NOISE AND SEAT -FLOOR VIBRATION

Evaluation on Unpleasantness The result of evaluation on unpleasantness is shown in Figure 2. As is shown in Figure 2, temporal variation in unpleasantness is observed from the onset of the sound exposure until the 20 minutes after the onset of the stimulus. Namely, car interior noise became more unpleasant in the first one third of the total exposure time and then the evaluations took rather stable values. From the more precise observation, evaluation became less unpleasant in the last 12 minutes under Noise alone condition. From the overall results, the evaluation obtained under high vibration condition was most unpleasant compared with other three vibration conditions.
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6 Lee mas

BEHAVIOR OF THE SECONDARY SOURCES AND EXAMINATION OF THE SOUND ENERGY FOR ACTIVE NOISE BARRIER

BEHAVIOR OF THE SECONDARY SOURCES AND EXAMINATION OF THE SOUND ENERGY FOR ACTIVE NOISE BARRIER

Without using the shielding thing, the active noise barrier (ANB) based on the boundary surface control can obstruct the sound by controlling the sound pressure and the acoustic impedance of the boundary surface. In this paper, we researched an appropriate arrangement of the secondary sources, and carried out the examination on the sound power output from the ANB. From the numerical analysis by boundary element method, it is desirable that the secondary sources are placed along the wave front made in the primary source.

6 Lee mas

Sound, meaning and politics The social construction of aircraft noise annoyance

Sound, meaning and politics The social construction of aircraft noise annoyance

Humans produce sounds and they hear each other’s sound. What is seen as noise, how much noise can be tolerated and who is allowed to produce the din, is not given with the sound itself. Aircraft noise annoyance is in part a social construction. Not so long ago, aircraft sound was highly regarded. These days, it is often linked to annoyance. The meaning of aircraft sound has changed. Growing noise exposure has contributed to that. But the growth alone does not account for irritation. I assume that the way we deal with annoyance politically has contributed to a change in perception. Noise policies, social movements and regulating institutions influence the way in which we think and feel about noise and annoyance. In the political process a definition of a problem emerges and is spreads. The public will adopt it, reject it or modify it. Policy measures and institutions shape private perception as well. If Swiss citizens are allowed to vote for or against public financing of Swiss airline in a referendum, this creates a sense of control. This feeling of control inhibits part of the annoyance. If, on the other hand, neighbors of London Heathrow, Frankfurt Airport or Amsterdam Schiphol get dissatisfied with their role in the policy process, this contributes to misfeasance and annoyance.
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7 Lee mas

ABSTRACT: Reducing sound pressure levels (SPL) from a noise source for improved acoustical quality in

ABSTRACT: Reducing sound pressure levels (SPL) from a noise source for improved acoustical quality in

ABSTRACT: Reducing sound pressure levels (SPL) from a noise source for improved acoustical quality in terms of speech intelligibility is the principal goal in multi-functional spaces. Speech intelligibility index (STI) calculated in noise is ‘STI in noise’, which is a quality indicator in multi-functional rooms. Screens blocking the direct sound from the noise source provides a good improvement in ‘STI in noise’ by reducing noise levels . This paper discusses the impact of design parameters of screens to reduce noise levels. The parameters effecting the acoustical performance of screens are discussed together with the architectural constraints. Screen parameters such as position, height, bottom gaps, absorption capacity, depth, width are investigated together with the space parameters such as absorptive ceiling and floor.
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8 Lee mas

ON THE USE OF SOUND METRICS TO EVALUATE NOISE FROM EVs AND HEVs - A LITERATURE REVIEW

ON THE USE OF SOUND METRICS TO EVALUATE NOISE FROM EVs AND HEVs - A LITERATURE REVIEW

The present work is framed within the above mentioned COST action, and its main goal is to perform a literature review related to the sound metrics to evaluate sound generated by EVs and HEVs, while displaying also results provided by previous research. Moreover, due to the existing problematic regarding the absence of noise in electric and hybrid vehicles at certain manoeuvres, strategies for warning sounds will be discussed. It is important to mention that the information gathered here was obtained from a literature review using the following sources: collaborative research projects such as Compett or eVADER; Regulations and Technical documentations provided by different organizations (United Nations Quiet Road Transport Vehicle (QRTV) working group, the National Highway Traffic Safety Administration (NHTSA) in the United States or the recent European Parliament draft legislation);papers available, mainly published in conferences but also in international referee journals; classical books on NVH of vehicles.
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8 Lee mas

A study of different calculation methods for noise barrier top edge designs

A study of different calculation methods for noise barrier top edge designs

First, sound pressure levels behind Type 1 barrier were compared. The first two results were calculated by the known Fresnel and Kurze & Anderson formulae, while the third graph is the result of the „Sysnoise” simulation. Results for the 121 nodes were calculated 4 m far from the barrier, at the height of 1 m.

5 Lee mas

HOW ACOUSTIC EXPERTS TALK TO “NORMAL PEOPLE”

HOW ACOUSTIC EXPERTS TALK TO “NORMAL PEOPLE”

Traffic noise, particularly vehicle noise, tyre noise and its relation to noise emission from roads was investigated in numerous projects. The same holds for noise emission from trains, due to knowledge about aerodynamic and structural-acoustic sources of wheel-rail contact. Detailed knowledge, too, is available for description and optimization of sound in cars, including tyre noise, pass-by noise, sound quality and sound design strategies. Much less knowledge, however, is available concerning the indoor sound in trains and the acoustic comfort for the passengers. Typical situations in local trains or subways, for instance, are characterized by the frequent stop and go from station to station. This noise scenario is very specific, even characterizing the city’s local train system acoustically. This observation leads to the question of sound quality in trains and to traveling comfort in subways which affects thousands and thousands of people going from home to work day by day. It is, therefore, obvious that aspects of sound quality are in the same amount relevant as for car industry.
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12 Lee mas

COMPARISON OF SUBJECTIVE RATINGS OF TONAL COMPONENTS WITH MODEL PREDICTIONS WITH SPECIAL CONSIDERATION OF TONE TO NOISE PROCEDURES AS PROPOSED IN E DIN 45681 AND ANSI S1.13

COMPARISON OF SUBJECTIVE RATINGS OF TONAL COMPONENTS WITH MODEL PREDICTIONS WITH SPECIAL CONSIDERATION OF TONE TO NOISE PROCEDURES AS PROPOSED IN E DIN 45681 AND ANSI S1.13

An original tire sound recorded in the laboratory with a dummy head sitting at the drivers seat served as “background-noise”. Pure tones of 500 Hz with T/N-ratios of 3, 6, 9, 12, 18 dB and narrow-band noises (NBN) centered around 500 Hz having bandwidths of 10, 50, 100 and 200 Hz were added to this “background”. The total power of the narrow-band noises was kept constant at the level of the pure tone having a T/N-ratio of 12 dB. All sounds were rated by 25 observers on a six point category scale ranging from "not tonal" to "very tonal".

6 Lee mas

NOISE FROM WIND TURBINES STANDARDS AND NOISE REDUCTION PROCEDURES

NOISE FROM WIND TURBINES STANDARDS AND NOISE REDUCTION PROCEDURES

Information on the sound power level and tonality of wind turbines is needed by planners, manufacturers and authorities. At present wind turbine noise specifications tend to be based on measurement results from a single turbine of a particular make and model and these are then taken to be representative of these turbines as a whole. Clearly this is unlikely to be the case, as there will be individual variation between different turbines. The intention of this document is to determine declared noise emission values from a sample of turbines of the same type. The declaration will increase the reliability of wind farm planning and shall facilitate the comparison of sound power levels and tonality values of different types of wind turbines.
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6 Lee mas

ANALYSIS AND DETECTABILITY IN URBAN ENVIRONMENTS OF AVAS FOR EVs AND HEVs

ANALYSIS AND DETECTABILITY IN URBAN ENVIRONMENTS OF AVAS FOR EVs AND HEVs

To evaluate the detectability of vehicles, sound samples from a pass-by test were acquired. These samples will be used during the psychoacoustic tests in order to reproduce the sound events more accurately. To do this, a Head Acoustic HSM III dummy head was used, with a frequency sample of 44100 Hz and a bit depth of 16 bits with noise shaping algorithm. A fifth order high- pass filter with cut-off frequency of 22 Hz was used during the acquisition. The dummy head was situated at 3 meters from the centre of the traffic lane. The sound acquisition was made from ±30 meters form the dummy head.
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8 Lee mas

ENVIRONMENTAL NOISE CONTROL IN THE PULP AND PAPER INDUSTRY

ENVIRONMENTAL NOISE CONTROL IN THE PULP AND PAPER INDUSTRY

Different absorptive and reactive silencer types with their individual octave band attenuation spectra versus their costs are always cost-optimized for each case. When the requirements are strict, e.g. a sound pressure level of 65 dB(A) at 1m distance from the discharge, a combinaton of absorptive and reactive silencers must be used to cover the whole frequency range. In case of vacuum pump exhaust air attenuation, a combination is also often required.

6 Lee mas

Pantograph noise measurements in Madrid-Sevilla high speed train (AVE)

Pantograph noise measurements in Madrid-Sevilla high speed train (AVE)

Afterwards, the sound power level value has been used as an input for a SEA model which also included vibro-acoustical characterization of the train elements [4]. Figure 8 shows the results of SEA modeling, it reveals that in the passengers zone under the pantograph this become the main source although it is not of the same importance along the rest of the train. As a consequence of the fact that the pantograph becomes the main source on its influence area, it was agreed with the train builder to reinforce the acoustical insulation of the roof with additional barrier/absorbent layers in the surroundings of the pantograph zone, in order to keep the estimated noise levels within specifications in this specific zone.
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8 Lee mas

SOUND-DESIGN DEVELOPMENT WITH SOUND SIMULATION VEHICLE

SOUND-DESIGN DEVELOPMENT WITH SOUND SIMULATION VEHICLE

As already stated either pure CAE-sounds or measured sounds may be auralized in real time. When measured sound are to be synthesized one need to follow certain measurement procedures for the power train part as well as for the wind and road noise part. On the power train side for instance various runups need to be performed. The whole engine speed range for several load conditions is to be measured in a test cell. The road and wind noise contribution need to be measured dependent on vehicle speed. All necessary auralization data are stored in a powerful computer which is installed in the boot of the vehicle. Via CAN bus all needed vehicle data such as engine speed, load condition and vehicle speed are transferred to the computer according to Fig.3.
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6 Lee mas

Color and Sound: Physical and Psychophysical Relations

Color and Sound: Physical and Psychophysical Relations

It is worth noting here that some people feel the sound produced by an instrument more colorful than the sound of a tuning fork, making the analogy in a direction oppo- site to the one proposed here. These opinions must be taken into account, since there is no guarantee that the physical analogy must coincide with the psychological one. Recently, I have begun experiments presenting peo- ple with series of sounds and series of colors, asking them to relate both sensations. One pair of these series involves sounds of different timbre and colors of different satura- tion. Though the experiments are not complete yet, the tendency shows that about 80% of the people relate pure sounds with saturated colors, complex sounds with duller colors, and noise with gray or achromatic colors (these results coinciding with the physical correlation), while only about 20% of the people make the opposite choice.
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9 Lee mas

ACOUSTIC EFFICIENCY OF FALSE CEILINGS: STUDY ON THE INFLUENCE OF DISTANCE FROM THE CEILING SLAB

ACOUSTIC EFFICIENCY OF FALSE CEILINGS: STUDY ON THE INFLUENCE OF DISTANCE FROM THE CEILING SLAB

To evaluate the changes in performance of these systems, 3 false ceilings were constructed at a distance from the supporting slab of 15 cm, 25 cm and 45 cm. The false ceilings are made of plasterboard with rockwoll on its back surface. To evaluate the performance of these systems against impact noise, the tapping machine was placed on the laboratory test bare floor. The sound levels spectra was recorded in the reverberation room. The efficiency of the systems was calculated with the follwing equations:

6 Lee mas

1 TOWARDS A QUALITATIVE NOISE MAP BASED ON MEASUREMENT AND PERCEPTION, THE CASE OF ROSSIO SQUARE IN LISBON

1 TOWARDS A QUALITATIVE NOISE MAP BASED ON MEASUREMENT AND PERCEPTION, THE CASE OF ROSSIO SQUARE IN LISBON

Let one specify, first, what one understands by quality in this paper. It is not about an aesthetic judgement of taste - on what is a «good» or a «bad» noise - obtained after consulting a segment of population. It’s not either about acoustical quality such as it is given by the psychoacoustics traditional criteria. Quality is defined here as the sound attribute of an object of perception. In other words, it is when a sound or a noise produces sense to the auditor, who attributes it a name by verbalisation, that one can speak about sound quality. Perception acts by a selection of the object to be listened, by designating and isolating it of its context [1]. Quality is related to the cognitive process, which involves the user in the analysis of sound information. All things considered, quality here answers the question: what does one listen at a precise point in space and how to report it to a map?
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6 Lee mas

Primeiros Ensaios para a Determinação de Nível de Potência Sonora de Furadeiras no Brasil

Primeiros Ensaios para a Determinação de Nível de Potência Sonora de Furadeiras no Brasil

ABSTRACT: In 1990, the Instituto Brasileiro do Meio Ambiente e dos Recursos Naturais Renováveis (IBAMA) established the “Programa Silencio” (www.ibama.gov.br), in Brasil. One of the actions of this program was created a label named Selo Ruído to inform the consumer about the sound power levels generated by electrical tools and equipments like hair dryer, vacuum cleaner, liquefier. The label will be emitted by laboratories approved by Instituto Nacional de Metrologia, Normalização e Qualidade Industrial (INMETRO). To measure the sound power levels is necessary develop test methods special for each sound source. This work shows the first results about determination of the sound power levels of eletric drills realized in the Laboratório de Conforto Ambiental, Faculdade de Engenharia Civil, Arquitetura e Urbanismo, Universidade Estadual de Campinas. The test procedure was based in international standards ISO 3743 Acoustics – Determination of sound power levels of noise sources using sound pressure- Engineering method for small, movable sources in reverberant fields- Part 1 Comparison method for hard-walled test rooms e Part 2 : Methods for special reverberation test rooms. The test rooms was qualified to measurements and the electric drills sound power levels was determinate. The results show that the proposed test method is indicated to apply in Selo Ruído
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8 Lee mas

A METHOD FOR THE ASSESSMENT OF SOUNDS AS PERCEIVED SEPARATELY FROM THEIR BACKGROUND

A METHOD FOR THE ASSESSMENT OF SOUNDS AS PERCEIVED SEPARATELY FROM THEIR BACKGROUND

The results showed that the introduction of human perception during the process of analysis and of treatment of the signal makes it possible to target measurements on one or more noise sources selected separately from their background noise. Contrary to conventional measurements, which yield overall values of LAeq, without distinguishing sources, the method presented here allows a space description of a soundscape by standing out each sound form from its context. It can measure the range of a noisy source in a given place, test the range or the masking of an urban device (fountain) or contribute to the decision and the design of a specific architectural project, for example.
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6 Lee mas

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