Noise Sources

Top PDF Noise Sources:

Behavior observation of major noise sources in critical care wards

Behavior observation of major noise sources in critical care wards

The patients in the critical care wards are often exposed to excessive levels of noises and activities. In particular, they tend to suffer from sleep distance at night, as a common problem [1]. Unfortunately, as shown in previous studies, the noise levels measured in the wards frequently exceeded the WHO (World Health Organization) guideline values by more than 20dBA [2-6]. Behavioural modification and improvement of major noise sources is considered to be an effective noise reduction strategy in the context of hospital acoustic environments [1]. However, very little observational data regarding noise sources in the healthcare environment exists, though there are some studies investigating the human activities related to interruptions on activity performance and communication in hospitals [7, 8]. Similar to the field measurement and simulation works presented in previous papers [9-12] , researchers have measured the noise levels or studied the sound field of various healthcare environments. In general, however, their results simply counted the frequency or number of occurrences of different noises together with the corresponding mean and standard deviation values, and described the possibilities of avoidable noises to provide noise control solutions, after indicating the dominant sources [5, 13, 14]. The necessary statistical analysis for the noise distribution, considering the variability of noise distribution over different time periods, wards, activities and routine procedures, are often ignored. Reliable behavioural observations for essential noise sources are still very limited.
Show more

39 Read more

Analysis and Classification of Noise Sources of Conveyor Systems by Sound Visualizing on the Postal Package Sorting Line

Analysis and Classification of Noise Sources of Conveyor Systems by Sound Visualizing on the Postal Package Sorting Line

Sound visualization tools are now widely used in industry. As a tool, acoustic cameras are also well- suited for fast- er identification of errors as well as individual states while operating devices. The aim of this paper was to locate and quantify noise sources on a packet sorting line using an acoustic camera and then to propose noise reduction measures. Localization of noise sources was performed by means of an acoustic camera with a microphone ring array. The result of these measurements and analyses was to sort the individual noise sources from less noisy to the noisiest, which gives a good assumption for better planning of spending on the implementation of noise reduction measures. The outputs of these measurements also give information on the character and frequency composition of the sound of individual sources, which will help out in the design of specific noise measures.
Show more

5 Read more

Article Small-scale rotor aeroacoustics for drone propulsion: a review of noise sources and control strategies

Article Small-scale rotor aeroacoustics for drone propulsion: a review of noise sources and control strategies

Abstract: In the last decade, the drone market has grown rapidly for both civil and military purposes. Due to their versatility, drones demand is constantly increasing, with several industrial players joining the venture to transfer urban mobility to the air. This has exacerbated the problem of noise pollution, mainly due to the relatively lower altitude of these vehicles and to the proximity of their routes to extremely densely populated areas. In particular, both the aerodynamic and aeroacoustic optimization of the propulsive system and of its interaction with the airframe are key aspects of the design of aerial vehicles for the success or the failure of their mission. The industrial challenge involves finding the best performance in terms of loading, efficiency and weight, and, at the same time, the most silent configuration. For this reason, research has focused on an initial localization of the noise sources and, on further analysis, of the noise generation mechanism, focusing particularly on directivity and scattering. The aim of the present study is to review the noise source mechanisms and the state-of-the-art technologies available in literature for its suppression, focusing especially on the fluid-dynamic aspects of low Reynolds numbers of the propulsive system and on the interaction of the propulsive-system flow with the airframe.
Show more

19 Read more

Indentification Of Noise Sources Using Principal Component Analysis

Indentification Of Noise Sources Using Principal Component Analysis

In building, sound can be generated by machines, air handling unit system, chiller, amplifier, computers and many more. To human when they are working this kind of sound might become annoying to them. Also for some quite places such as library and hospital much noise can be a threat to people in those building. Even ringtone from hand phone can become a noise.

24 Read more

The characterization of residential impedances and noise sources for power line communications

The characterization of residential impedances and noise sources for power line communications

The 240 volt noise measurements were ~de using the 240 volt filter which is a high pass filter whose input i~ the 240 volt line eo line voltage and whose output is a volcage referenced t[r]

131 Read more

Identification of Noise Generated by Driving Set of Autogyro Using an Acoustic Camera

Identification of Noise Generated by Driving Set of Autogyro Using an Acoustic Camera

The advantages of using an acoustic camera used to analyze of noise distribution in relation to aircraft were discussed. Location of noise sources was based on example of autogyro model. The re- sults of the research confirm that the main source of noise in the autogyro is its propeller. In pictures showing the map of acoustic pressure (Figure 5 and 6), it is clear that the main source of noise is occurring near the propeller. The results of the research will be used to construct a new “Safe- Gyro” aircraft designed to increase the safety of flight, as well as the possibility of vertical take- off and landing of an autogyro.
Show more

5 Read more

Studies in aeronomy, astrophysics, and astronomy, and, Fluctuations, noise and quantum electronics

Studies in aeronomy, astrophysics, and astronomy, and, Fluctuations, noise and quantum electronics

Universal noise equivalent circuit for ideal bipolar junction and photon transport transistors showing three independent physical noise sources: shot noise base-emitter voltage generator[r]

344 Read more

Sources of Noise Pollution in Mashhad Railway Station

Sources of Noise Pollution in Mashhad Railway Station

20. 20-Rasmussen G. Determination of sound power levels of noise sources using sound intensity points versus scanning. [POSTER] at: proceeding of the International congress on noise control engineering; 1996 Jul 30- Aug 2. Liverpool, UK. St Albans: Institute of Acoustics; 1996.

7 Read more

NOISE REDUCTION TECHNIQUES FOR FORCED DRAFT FAN IN THERMAL POWER PLANT USING REACTIVE SILENCER

NOISE REDUCTION TECHNIQUES FOR FORCED DRAFT FAN IN THERMAL POWER PLANT USING REACTIVE SILENCER

Power station or power plants are industrial facility for electric power generation. Since the early advent of ‘steam engine’ technology and ample availability of coal and reliable cheap power, people all over the world heavily rely on thermal power stations, but Thermal power plants are one of the noisiest factories. However Prolong exposure to industrial noise can't be neglected, which may cause neurobehavioral change, psychological stress, and unhappiness in daily life without showing the symptoms of chronic / acute diseases. For Thermal power plants, the major noise sources are coal unloading plant, crusher plant, compressor, boiler feed pump, turbine, Forced Draft Fan (F.D. fan), Induced Draft Fan (I.D. fan etc. This paper aims to study different type of noise sources and Silencers used in Thermal power plants and also analyzes the noise source of Forced Draft Fan (F.D. fan) and reduce the noise by a modified reactive Silencer or Muffler.
Show more

5 Read more

Noise source identification for ducted fans

Noise source identification for ducted fans

U n d e rstan d in g com bustion noise source m echanism s, designing efficient acoustic liners an d optim ising active control alg o rith m s for noise red u ctio n requires th e identification of th e frequency and modal co n ten t of th e com bustion noise co n trib u tio n . An acoustic m easurem ent of a system of in terest will m ost often be th e su n m iatio n of a num ljer of sep arate acotistic sources along w ith som e extraneous noise. F igure 1.1 illu stra te s th e principle noise sources in an aero-engine. For th e case w here it is not possible to rem ove individual sources w ith o u t effecting the behaviour of th e o th e rs, th e challenge is to decom pose th e m easu rem en t signal into its co n stitu en t ])arts. For acoustic sources th a t are consid­ ered to be s ta tio n a ry ran d o m processes w ith zero m ean and w here system s are c o n sta n t-p a ra m ete r linear system s, figure 1.2, a m u ltip le -in p u t/sin g le-o iitp u t m odel, can be used to rep resen t th e sys­ tem . T he e x tra n e o u s noise term , n{t). accom m odates all deviations from th e m odel, such as acoustic sources g re a te r th a n M w hich are unaccounted for. n o n -statio n ary effects, acquisition, in stru m en t and m ath e m a tic a l noise along w ith u n ste a d y press\ne fluctuations local to th e sensor, such as flow or h y d ro d y n am ic noise. As th e acoustic noise sources in an aero-engine overlap in th e frequency dom ain, w ith vary in g am p litu d es, as show n in figure 1.3. it can be difficult to q u an tify th e individual co n trib u tio n s. O ne of th e p rin cip al objectives of this thesis is to develop alg o rith m s to accurately identify th e com bustion noise co n trib \itio n to a far-field acoustic m easurem ent.
Show more

180 Read more

Sound Source Localisation for a High-Speed Train and Its Transfer Path to Interior Noise

Sound Source Localisation for a High-Speed Train and Its Transfer Path to Interior Noise

at high speeds. Sheng et  al. [11] extended the Fourier- transform-based method to obtain revised equations that are appropriate for predicting sound radiation from slab high-speed railway tracks. Zhang et al. [12] investigated the effects of ballast on sound radiation from the rail- way track, with the conclusion that ballast vibration can increase the sound radiation by 1–4.5 dB for frequencies between 20 Hz and 300 Hz at the full scale, whereas at higher frequencies the effect is negligible. Nagakura [13] performed wind tunnel tests using a 1/5 scale Shinkansen train model and analysed the distribution of aerodynamic noise sources. Latorre Iglesias et al. [14] proposed a semi- empirical component-based model to predict the aerody- namic noise from train pantographs.
Show more

16 Read more

Willingness to pay for noise abatement in Singapore

Willingness to pay for noise abatement in Singapore

While these studies have attempted to correlate the valuation of annoyance reduction to the benefits of a physical measure of noise, the data required for such a correlation may be difficult to obtain. If the survey included additional questions on the annoyance associated with common noise sources, respondents must accurately remember the loudness of these different noise sources. However, Galilea & Ortúzar (2005) found that when respondents were asked to rank, from memory, road intersections with objectively different levels of noise, their responses did not correlate with the actual level of noise at the intersections, indicating that respondents’ memory of noises may not be precise. Further, noise measurement and acoustic modelling of urban areas require extensive data collection at respondents’ homes. Finally, the transfer of annoyance levels from physiological studies imposes strong assumptions on respondents’ annoyance with noise. Specific to Kim et al. (2019), all respondents are assumed to have a lower annoyance threshold of 42dB, which may not be accurate given that this threshold was transferred from a European context to estimate annoyance thresholds in Korea.
Show more

353 Read more

A Sub-µW Tuneable Switched-Capacitor Amplifier-Filter for Neural Recording Using a Class-C Inverter

A Sub-µW Tuneable Switched-Capacitor Amplifier-Filter for Neural Recording Using a Class-C Inverter

b) Effect of On-Resistance Thermal Noise of Switches The two switches that appear ON in this phase (i.e. and ) are modeled as and . Each one generates a white noise PSD equal to (Fig. 5). Since, the noise sources are uncorrelated, the transfer function from each one to the output can be find separately to find the contribution of each one on the entire output noise power. Hereafter, it is assumed both switches have the same for simplicity.

8 Read more

Evaluation of geoelectrical noise in urban area: A case study in Hanoi, 
		Vietnam

Evaluation of geoelectrical noise in urban area: A case study in Hanoi, Vietnam

Due to technological growth man-made electromagnetic noise is nowadays superimposed on natural noise almost everywhere on Earth. Especially in urban areas, where the distortion of geoelectrical data are mainly caused by several human generated noise sources such as power lines, traffic vehicles, telecommunication systems [Bianchi and Meloni, 2007; Szarka, 1988]. Rapidly expanding cities space requires more geological structure investigations before infrastructure constructions work. So, geoelectrical method is still a good choice for this work because of its cost effective, but noise is always a challenge.
Show more

5 Read more

Human response to vibration in residential environments (NANR209), technical report 4: calculation of noise exposure

Human response to vibration in residential environments (NANR209), technical report 4: calculation of noise exposure

Noise sources from construction and railway traffic were covered in this report. Although both sources were found to be subjectively annoying, construction work could potentially invoke a much higher negative annoyance response. The details pertaining to associated problems with annoyance can be found in Technical Report 6 “Determination of exposure response relationship” (Woodcock et al., 2011) and Technical Report 5 “Analysis of The Social Survey Findings” (Condie & Steele, 2011). It was observed that construction activities typically occur within close proximity to residential environments. This could perhaps be the most important aspect influencing upon a resident’s reaction. Annoyance can be caused not only by reception of sound or noise, but also by visible effects such as the visual presence of construction work. These factors can also invoke additional adverse effects. As a growing number of construction projects are performed in the vicinity of residential environments, the surrounding community could perhaps find them increasingly annoying. Although primarily due to noise level, other exposures such as vibration, which calculation can be found on Technical Report 3 “Calculation of vibration exposure” (Sica et al., 2011), dust, light etc. may also significantly influence upon overall annoyance (Condie & Steele, 2011).
Show more

69 Read more

Download
			
			
				Download PDF

Download Download PDF

The measured noise levels in decibels plotted against distance in meters for each of the four noise routes are shown in Figures 2 to 5. Route A (plot RA) shown in Fig.2 covers a total distance of 700 meters measured from the road crossing (The reference point B); that is, on the fence. At the bench mark (BM) or reference point R, NL was 97.4 dB (A) and increased to 82 dB (A), 100 meters away from the bench mark due to the proximity of a noise source in the process unit. Along this route, certain major noise sources were located such as pumps, steam traps, compressors and blending plants. Beyond the 100m points, the noise level fell to 76 dB (A). About an additional 60m away it rose to 81 dB (A), to 83 dB (A) in the next 40m points and then, 60m away fell to 75 dB (A). It rose to 88 dB (A) in another 180m and finally fell to 70 dB (A) on the fence, all depicting a non linear variation As evident from the plot RA, as the noise level dispersed away from source way sudden rise indicated proximity to a fresh noise source.
Show more

12 Read more

1998 Digital Signal Processing Solutions

1998 Digital Signal Processing Solutions

Therefore, as long as the noise sources arise from separate mechanisms and are independent, which is usually the case, the average mean square value of a sum of separate independent noise sources is the sum of the individual average mean square values. Thus in our example E = ∫ 4kT(R t 2 1 + R 2 )df, which is what would be expected. This is derived using voltage sources, but also is true for current sources. The same result can be shown to be true when considering two independent sine wave sources.

27 Read more

Noise Reduction of a Novel Phase-Locked Coherent Optical Phase Demodulator

Noise Reduction of a Novel Phase-Locked Coherent Optical Phase Demodulator

The optical phase-lock demodulation technique has been utilized with the implementation of additional feedback to reference signal by phase modulation to LO signal. In this system, the receiver sensitivity is highly dependent on the costly optical sources and photo-detectors. Also, these components are responsible for the predominant noise sources i.e., phase noise and shot noise. The input reference signals after long distance travel through optical fibre is very weak in strength and for good reception, relatively high power LO signal is modulated with it. The inevitable quantum detection shot noise and random phase generation to the phase part of Laser broadens the spectral
Show more

6 Read more

Non linear Identification Applied to Broadband Turbomachinery Noise

Non linear Identification Applied to Broadband Turbomachinery Noise

An analysis was performed on the experimental rig to detect the presence of non-linearities. In order to investigate the hypothesis that upstream broadband noise might interact with a rotor/stator pair to produce acoustic energy at sum and difference frequencies band limited noise was radiated from the speaker. Figure 10 shows the sound pressure level at a location downstream of the vane-axial fan using a microphone flush mounted with the inside of the duct. Three test configurations are shown. The first power spectral density (PSD) in red shows the energy measured by the microphone when band limited noise of 10.5 − 11kHz is emitted from the speaker. The plot in green shows the PSD when the speaker is turned off and the vane-axial fan is turned on. The fan has a high rotational speed of 16500rpm at the nominal max design voltage of 26VDC. As the fan has 8 blades this would result in a nominal blade pass frequency (BPF) of 2200Hz. In this test the rpm is lower with the BPF occuring at approximately 1600Hz a peak at which can be seen in the figure, as are its harmonics, nBPF, four of which are visible and are indicated with black dashed lines. The third test configuration in this figure is for the case where both the vane-axial fan and speaker operate simultaneously. It is clear, from observation of the blue PSD, that in addition to the 500Hz band of energy emitted from the speaker, bands of noise are frequency scattered to either side in accordance with ±BP F . This result is highly significant as noise is generated in frequency ranges which cannot be attributed to the simple superposition of the noise sources.
Show more

15 Read more

Street-level noise in an urban setting: assessment and contribution to personal exposure

Street-level noise in an urban setting: assessment and contribution to personal exposure

Perhaps the most important contributor to the urban soundscape is street-level sound. Given the ubiquitous exposure to street-level sounds among urban dwellers, and the potential for annoyance and health effects from this noise, strict urban noise control measures for street- level sources of noise are increasingly being imple- mented. However, even in cities such as New York City (NYC), which has rigorous regulations on, and enforce- ment of, nuisance noise sources (e.g., loud radios and car alarms) and construction–related noise, there is little focus on street-level noise (e.g., noise from roadway traf- fic, commercial activities, etc.,), though some studies have evaluated noise from mass transit in NYC [19,20]. The extent and magnitude of levels of street noise and air pollutants in NYC has recently been assessed [21], but the methodology used did not measure personal ex- posures, but rather levels at 10 ft above street level, well above the elevation of the heads of pedestrians. Variation in street-level noise with regards to vehicle traffic and road proximity has been explored, [18] but most studies on traffic noise have relied on modeling of noise levels from a network of roads, land use regression, or extrapo- lation of models based on a small number of noise sam- ples [22-24]. While these are cost-effective approaches to estimate traffic noise levels, they can neglect factors in the urban built and natural environment that may mitigate or exacerbate exposure to street noise levels, in- cluding temporal changes in noise, built environment factors, and vulnerable areas and individuals. These other factors have particular relevance for understanding exposure to street-level noise in the urban environment.
Show more

10 Read more

Show all 10000 documents...