scholarly journals Noise Reduction Interventions in the Urban Environment as a form of Control of Indoor Noise Levels

2015 ◽  
Vol 78 ◽  
pp. 1653-1658 ◽  
Author(s):  
A. Magrini ◽  
A. Lisot
Keyword(s):  
Noise Reduction ◽  
Urban Environment ◽  
Noise Levels

Noise reduction of enhanced acoustic balconies on a high-rise building block

2021 ◽  
Vol 263 (1) ◽  
pp. 5327-5334
Author(s):  
SK Tang ◽  
Rudolf YC Lee
Keyword(s):  
Noise Reduction ◽  
Natural Ventilation ◽  
Traffic Noise ◽  
Elevation Angle ◽  
Noise Levels ◽  
Indoor Space ◽  
New Device ◽  
Air Inlet ◽  
The Difference ◽  
The Impact

A new device called 'enhanced acoustic balcony' is installed in a new housing estate in Hong Kong. It is intended to help reduce the impact of traffic noise on the residents. This balcony is basically an enlarged form of a plenum window and with three openings. Apart from the outdoor air inlet, there is the balcony door and a side-hung window on the interior balcony wall for natural ventilation of the indoor space. Sound absorption of NRC 0.7 is installed on the balcony ceiling and its sidewall facing the incoming traffic noise and an inclined panel is installed outside the balcony to provide noise screening. A site measurement of its noise reduction is carried out in the present study in a newly completed housing block. A 28 m long loudspeaker array is used as the sound source. The indoor noise levels are measured according to ISO standard. The results show that the difference between indoor and outdoor noise levels in the presence of this balcony form varies over a relatively narrow range between 10 to 13 dBA for an elevation angle from 25 to 60 deg. There is a weak increase of the noise level difference with elevation angle.

Optimized Asphalt Mixtures for Noise Reduction in Lithuanian Roads

2014 ◽  
Vol 614 ◽  
pp. 618-621
Author(s):  
Audrius Vaitkus ◽  
Tadas Andriejauskas ◽  
Laura Čygaitė ◽  
Jurgita Židanavičiūtė
Keyword(s):  
Noise Reduction ◽  
Noise Pollution ◽  
Low Noise ◽  
Asphalt Pavements ◽  
Noise Levels ◽  
Road Noise ◽  
Negative Effects ◽  
Development Experience ◽  
Growing Economy ◽  
Generation Mechanisms

In the world of growing economy and population, the need of transportation is rapidly increasing also raising problems of noise pollution. Environmental noise levels are increasing in parallel with increasing traffic flows resulting negative effects for society, wildlife and economy. The article gives an overview about the main transport noise source tyre/road noise, its generation mechanisms and influencing factors. One of the most effective and promising tyre/road noise solutions is low noise pavements, which has different noise reduction approaches. Low noise asphalt pavements and theoretical noise reduction principles are analysed in the paper as well as the development experience of particular low noise asphalt pavements for Lithuanian conditions.

Shockwave and Noise Abatement of Transonic Fans

2004 ◽  
Author(s):  
Liping Xu
Keyword(s):  
Shock Wave ◽  
Noise Reduction ◽  
Three Dimensional ◽  
Leading Edge ◽  
Aerodynamic Performance ◽  
Test Results ◽  
Shock Strength ◽  
Noise Levels ◽  
Noise Abatement ◽  
Blade Passage

The aerodynamic sources of the forward tone noise of transonic civil fans are analysed. The leading edge shockwave near the rotor tip section is identified as the main source of tone noise. By comparing the tone noise levels of the same fan operating at two different working lines, numerical calculations show that on the lower working line, the main passage shockwave is swallowed and locked into the blade passage, and the fan blades act as a shield to prevent the strong passage shock wave from propagating upstream. The calculations show that, by running the fan at a lower working line, up to 6 db abatement in the blade passing frequency (BPF) tone can be achieved through shielding the shockwave. With three dimensional CFD it is possible to design swept rotors which have desired shockwave structures near the tip region. Fan rotors with different swept leading edges have been designed to study this effect and comparisons in aerodynamics performances as well as the tone noise levels are made. It is predicted that in a swept rotor the leading edge shock strength can be further weakened and up to 5db further reduction in tone noise is possible. With a more secure shockwave shielding, a forward swept rotor has the combination of better aerodynamic performance and better noise abatement feature. The design and test results of a three dimensional fan rotor LNR2, featuring localised forward swept rotor are presented. Rig test results show that although the noise reduction through shock shielding has been demonstrated, the aerodynamics and noise are complicated by the problems specific to such localised forward swept fan.

Paper 16: A Study of Tractor Noise Control

1969 ◽  
Vol 184 (17) ◽  
pp. 149-169
Author(s):  
J. Matthews ◽  
J. D. C. Talamo
Keyword(s):  
Hearing Loss ◽  
Diesel Engine ◽  
Noise Reduction ◽  
Noise Level ◽  
Exhaust System ◽  
Low Noise ◽  
Acoustic Features ◽  
Noise Levels ◽  
Engine Design ◽  
High Incidence

A high incidence of hearing loss has been encountered among tractor drivers, and noise levels are shown to be further increased by the addition of cabs, particularly those which are structurally strong to resist crushing if the vehicle overturns. Some reductions in the noise level of the operator's environment can be obtained by covering the engine or by exhaust system modifications, while possible future improvements to diesel engine design may effect a significant improvement. However, it is proposed that noise reduction is likely to be achieved by attention to acoustic features of the operator's cab. The inclusion of resilient mounts, substantial floors and bulkheads, and acoustically absorbent linings are all shown to provide worthwhile improvements and, in combination, these measures can reduce noise levels from more than 100 dBA to 90 dBA or less. Where the tractor is fitted with a safety frame only, a low noise fabric cladding is shown to be feasible.

Noise Reduction in Ducts Achievable by Point Control

1998 ◽  
Vol 120 (2) ◽  
pp. 216-223 ◽  
Author(s):  
K. A. Morris
Keyword(s):  
Noise Reduction ◽  
Closed Loop ◽  
Noise Control ◽  
Active Noise Control ◽  
Practical Interest ◽  
Noise Levels ◽  
Sensors And Actuators ◽  
One Dimensional ◽  
Active Noise ◽  
Point Control

Noise control in a one-dimensional duct is analyzed. This problem is of practical interest and is also simple enough that a complete theoretical analysis is possible. It is shown that the optimal controller leads to an unstable closed loop. The noise reduction level achievable with a stable closed loop is calculated for arbitrary choices of sensor and actuator locations. This enables the best placement of sensors and actuators to be determined. Also, the analysis indicates that a “spatial waterbed” effect exists in some configurations of active noise control: i.e., that noise levels are increased for points outside of the region over which the design is done.

scholarly journals Noise reduction using a Bayesian penalized-likelihood reconstruction algorithm on a time-of-flight PET-CT scanner

2019 ◽  
Vol 6 (1) ◽  
Author(s):  
Paulo R. R. V. Caribé ◽  
M. Koole ◽  
Yves D’Asseler ◽  
B. Van Den Broeck ◽  
S. Vandenberghe
Keyword(s):  
Noise Reduction ◽  
Expectation Maximization ◽  
Time Of Flight ◽  
Penalized Likelihood ◽  
Reconstruction Algorithm ◽  
Patient Data ◽  
Noise Levels ◽  
Patient Study ◽  
Phantom Data ◽  
Pet Ct

Abstract Purpose Q.Clear is a block sequential regularized expectation maximization (BSREM) penalized-likelihood reconstruction algorithm for PET. It tries to improve image quality by controlling noise amplification during image reconstruction. In this study, the noise properties of this BSREM were compared to the ordered-subset expectation maximization (OSEM) algorithm for both phantom and patient data acquired on a state-of-the-art PET/CT. Methods The NEMA IQ phantom and a whole-body patient study were acquired on a GE DMI 3-rings system in list mode and different datasets with varying noise levels were generated. Phantom data was evaluated using four different contrast ratios. These were reconstructed using BSREM with different β-factors of 300–3000 and with a clinical setting used for OSEM including point spread function (PSF) and time-of-flight (TOF) information. Contrast recovery (CR), background noise levels (coefficient of variation, COV), and contrast-to-noise ratio (CNR) were used to determine the performance in the phantom data. Findings based on the phantom data were compared with clinical data. For the patient study, the SUV ratio, metabolic active tumor volumes (MATVs), and the signal-to-noise ratio (SNR) were evaluated using the liver as the background region. Results Based on the phantom data for the same count statistics, BSREM resulted in higher CR and CNR and lower COV than OSEM. The CR of OSEM matches to the CR of BSREM with β = 750 at high count statistics for 8:1. A similar trend was observed for the ratios 6:1 and 4:1. A dependence on sphere size, counting statistics, and contrast ratio was confirmed by the CNR of the ratio 2:1. BSREM with β = 750 for 2.5 and 1.0 min acquisition has comparable COV to the 10 and 5.0 min acquisitions using OSEM. This resulted in a noise reduction by a factor of 2–4 when using BSREM instead of OSEM. For the patient data, a similar trend was observed, and SNR was reduced by at least a factor of 2 while preserving contrast. Conclusion The BSREM reconstruction algorithm allowed a noise reduction without a loss of contrast by a factor of 2–4 compared to OSEM reconstructions for all data evaluated. This reduction can be used to lower the injected dose or shorten the acquisition time.

Effects of Sand Bed Anti-Vibration Mount on Transmitted Noise from Portable On-Site Electricity Generator

2020 ◽  
Vol 15 (2) ◽  
pp. 8-12
Author(s):  
A.S. Aremu ◽  
T.K. Amao ◽  
O.A. Mokuolu
Keyword(s):  
Particle Size ◽  
Noise Reduction ◽  
Fine Sand ◽  
Sound Level ◽  
Sand Particle ◽  
Particle Sizes ◽  
Noise Levels ◽  
Noise Measurements ◽  
Level Meter ◽  
Vibration Noise

This study investigated the effect of different particle sizes of sand bed anti-vibration mount on transmitted noise from a portable on-site electricity generator. Ten sand bed anti-vibration mounts, 650mm x 650mm in cross section and 75mm thickness were prepared with particle sizes ranging from 0.09 to 2.30mm. Noise measurements were taken in the four cardinal directions using Extech HD600 digital sound level meter. The results of the study showed that the ability of the sand particles to dampen vibration noise from the portable electricity generator reduces with increase in particle size. The sand bed anti-vibration mounts reduced noise levels by 0.11 to 2.78 dB(A). However, fine sand bed of particle size 0.09mm and 0.15mm exhibited superiority in noise reduction over all other sand beds. In order to achieve appreciable noise reduction, the use of ISO 14688-1:2002 fine sand category is recommended as anti-vibration mount in combination with other damping methods. Keywords: Electricity generator, noise, sand, particle size and attenuation

The Hospital (Not So) Quiet Zone: Creating an Environment for Patient Satisfaction Through Noise Reduction Strategies

2019 ◽  
Vol 12 (4) ◽  
pp. 197-202 ◽  
Author(s):  
Linda Walker ◽  
Cherry A. Karl
Keyword(s):  
Patient Satisfaction ◽  
Noise Reduction ◽  
Visual Cues ◽  
Online Survey ◽  
Well Being ◽  
Hospital Environment ◽  
Noise Levels ◽  
Telephone Interviews ◽  
Patient Surveys ◽  
Reduction Strategies

Purpose:To determine whether using existing noise reduction strategies improves patients’ overall satisfaction level during hospitalization on an adult outpatient cardiology unit and to assess whether noise reduction strategies were effective to decrease the ambient noise for both staff and patient environments.Background:Excessive noise is a worldwide problem facing hospitals today. Noise has been proven to be detrimental to staff and patient well-being and hospital environment satisfaction levels.Intervention:Staff noise perception online surveys, a poster presentation, and education of noise reduction strategies were completed. Two 6-week phases of pre- and postimplementation noise reduction strategies were initiated including closing of the doors, verbal and visual alarm reminders for staff, posting quiet signs, and limiting equipment through the unit. Patient telephone interviews regarding the noise environment during hospitalization in both phases and a follow-up staff noise perception online survey were completed.Results:Staff surveys identified noise as an issue on the unit with staff communication (90%) being the main source. This correlated with patient surveys of five rooms closest to the desk considering the unit “noisy.” Post-implementation patient surveys noted that strategies created in helping the unit become “quiet/mostly quiet.” Closing patient doors was most effective in noise reduction, increasing patient unit satisfaction.Conclusion:The use of visual cues and staff education are effective in reducing noise levels. Decreased noise levels improved overall patient satisfaction with their hospital experience and created a less stressful work environment.

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