Using sound pressure level and vibration velocity method to determine sound reduction index of lightweight partitions

2019 ◽  
Vol 26 (2) ◽  
pp. 109-120
Author(s):  
AM Shehap ◽  
Abd Elfattah A Mahmoud ◽  
Hatem Kh Mohamed
Keyword(s):  
Sound Pressure Level ◽  
Sound Pressure ◽  
Cost Effective ◽  
Pressure Level ◽  
Vibration Velocity ◽  
Building Structures ◽  
Cost Effective Method ◽  
Cavity Filling ◽  
Sound Reduction ◽  
Reduction Index

Nowadays, lightweight building structures are widely used by the construction industry as a more natural and cost-effective method. The purpose of this study is to compare between sound pressure level and vibration velocity method for sound reduction index determination for single- and double-leaf gypsum board partitions. The sound pressure level method was carried out according to the requirements of ISO 140-3:1997, and the vibration velocity method (V) was carried out according to some criteria of ISO 10848-1:2006. Regarding double-leaf partitions, measurements were carried out with the leaves separated by 5- and 10-cm air gaps. The effect of cavity filling with absorbing materials was studied experimentally. The space between the leaves was filled with Rockwool and polyurethane to illustrate the effect of cavity absorption on the sound reduction index behavior. It was found that there is good agreement between the two methods. Also, cavity filling with a 10-cm absorbing material such as Rockwool increases the sound reduction index at the critical frequency by 7 dB using sound pressure method and 4 dB using vibration velocity method.

The Role of Static Pressure and Temperature in Building Acoustics

2003 ◽  
Vol 10 (2) ◽  
pp. 159-176 ◽  
Author(s):  
Volker Wittstock ◽  
Christian Bethke
Keyword(s):  
Sound Pressure Level ◽  
Sound Pressure ◽  
Static Pressure ◽  
Meteorological Conditions ◽  
Pressure Level ◽  
Shell Structures ◽  
Noise Levels ◽  
Sound Pressure Levels ◽  
Sound Reduction ◽  
Reduction Index

The influence of static pressure and temperature on sound reduction indices, impact sound pressure levels, improvements of impact sound pressure levels and sound reduction indices, and relative installation noise levels is investigated. Theory revealed a systematic influence on sound reduction index and normalized impact sound pressure level. Firstly, the sound power radiated by a vibrating structure is directly proportional to the sound impedance in air and therefore to static pressure and temperature to the power of −0.5. Secondly, the sound pressure produced in a room by a sound source also depends on sound impedance, i.e. on static pressure and temperature. Since the excitation of a test specimen is not influenced by static pressure or temperature, the two effects are not compensated by any other mechanism, thus temperature and static pressure also influence sound reduction index and normalized impact sound pressure level. Experimental verification involved measurement of sound reduction index in a small test suite at static pressures between 307 and 970 hPa. Measurement results for single-shell structures showed the expected behaviour, whereas results for double-shell structures revealed a considerable scatter with a tendency towards even larger temperature and static pressure influences. For comparison of the acoustic properties of building elements, it is therefore advisable to introduce a normalized sound reduction index and a normalized impact sound pressure level, with both referred to reference conditions of static pressure and temperature. Improvements in impact sound pressure levels and sound reduction index, and relative installation noise levels are determined from changes in sound level differences. Since each difference is influenced in the same manner by meteorological conditions, the resulting improvement is independent of static pressure and temperature, as long as the differences were determined under the same meteorological conditions.

Loudness of Structure-Borne Sound Heard Directly by Ear Put on Vibrating Structure

2003 ◽  
Vol 22 (1) ◽  
pp. 27-32
Author(s):  
Takuya Fujimoto
Keyword(s):  
Sound Pressure Level ◽  
Contact Surface ◽  
Vibration Amplitude ◽  
Sound Pressure ◽  
Pressure Level ◽  
Vibration Velocity ◽  
The Relationship ◽  
Velocity Level

Putting an ear close to a vibrating structure like a wall or a floor, we are able to hear structure-borne sounds clearly, but the loudness of such sounds has never been studied quantitatively. In this study, subjective experiments were carried out in order to obtain the relationship between loudness and the vibration amplitude of the ear's contact surface at low audible frequencies. The main result of this study is that the loudness of a structure-borne sound is almost equal to that of an air-borne sound with a sound pressure level 20 dB higher than the vibration velocity level (ref=5×10−8 m/s) of the surface. According to this result, the loudness of the structure-borne sound heard directly can be evaluated as a sound pressure level derived from the measured vibration amplitude of the structure.

Noise Abatement From Large Size Electric Generators

2005 ◽  
Author(s):  
Wei Tong
Keyword(s):  
Sound Pressure Level ◽  
Sound Pressure ◽  
Near Field ◽  
Cost Effective ◽  
The United States ◽  
Pressure Level ◽  
Environmental Sound ◽  
Industrial Noise ◽  
Large Size ◽  
Electric Generators

Growing environmental sound concerns and recognition that lengthy unprotected exposure to high industrial noise levels can be detrimental to man have resulted in increased attention to reducing industrial noise. In the United States, it is required by law that all turbomachinery manufacturers must provide acoustic guarantees to their customers. For instance, for majority of generators, the near field sound pressure level is usually guaranteed not to exceed 85 dBA. To accomplish this goal, a number of methods of noise reduction have been developed in power industry. As one of the most practical and cost-effective solutions, acoustic blankets have been designed and tested for using on large size electric generators to efficiently reduce their sound pressure levels. This work has successfully demonstrated the potential of acoustic blankets for improve the passive acoustic transmission characteristics from generators. The acoustic data obtained from a field test have shown that the blankets can reduce the overall sound pressure level from large size generators about 4 to 6 dBA.

Case study: Evaluation of noise reduction in frequencies and sound reduction index of construction with variable noise isolation

2020 ◽  
Vol 68 (3) ◽  
pp. 199-208
Author(s):  
Tomas VilniÅ¡kis ◽  
Tomas JanuÅ¡eviÄ?ius ◽  
Pranas BaltrÄ—nas
Keyword(s):  
Sound Pressure Level ◽  
Sound Pressure ◽  
Pressure Level ◽  
Glass Wool ◽  
Noise Attenuation ◽  
Engineering Equipment ◽  
Sound Levels ◽  
Air Supply ◽  
Study Evaluation ◽  
Sound Reduction

Intense sound levels produced by engineering equipment have become an acute issue. As most of engineering equipment require air supply, exhaust and good ventilation, it is not possible to control the noise by covering them with tight hoods. Louver with blades covered with acoustic materials and gaps that enable free circu- lation of air are used to this end. Three louver configurations were tested in the semi-anechoic chamber: bare metal louver blades, louver with blades covered with 20-mm-thick polystyrene foam slabs on both sides, and louver with blades covered with 15-mm-thick glass wool slab. According to the test results, louver with blades covered with glass wool slab demonstrated the best noise attenuation characteristics. The reduction of equiv- alent sound pressure level subject to blade inclination angle was from 10.8 to 12.5 dB. Sound pressure level reduction by louver with blades covered with poly- styrene foam slabs was weaker: the reduction of equivalent sound pressure level was from 5.4 to 8.4 dB. Louver with blades not covered with any acoustic material demonstrated the least noise attenuation result from 1.9 to 3.9 dB

Structure-borne sound in buildings: Advances in measurement and prediction methods

2020 ◽  
Vol 68 (1) ◽  
pp. 1-20 ◽  
Author(s):  
Barry Marshall Gibbs ◽  
Michel Villot
Keyword(s):  
Sound Pressure Level ◽  
Sound Pressure ◽  
Prediction Models ◽  
Pressure Level ◽  
International Standards ◽  
Sound Insulation ◽  
Wide Range ◽  
Source Data ◽  
Sound Reduction ◽  
The Impact

This article coincides with recent publications of international standards, which provide methods of predicting the performance of both heavyweight and lightweight buildings in terms of airborne sound insulation and impact sound isolation, from the performance of individual elements such as walls and floors. The performances of the elements are characterized by the sound reduction index and the impact sound pressure level. To predict the sound pressure level due to vibrating sources (i.e., mechanical installations, water services and other appliances), source data are required in a form appropriate as input for prediction models similar to the above, i.e., as equivalent single quantities and frequency band-averaged values. Three quantities are required for estimating the structure-borne power for a wide range of installation conditions: activity (the free velocity or the blocked force of the operating source), source mobility (or the inverse, impedance) and receiver mobility (or impedance) of the connected building element. Methods are described for obtaining these source quantities, including by using laboratory reception plates. The article concludes with a proposed database, based on laboratory measurements and simple mobility calculations, which provides a practical approach to predicting structureborne sound in buildings.

Contributions of Voice and Nonverbal Communication to Perceived Masculinity–Femininity for Cisgender and Transgender Communicators

2020 ◽  
Vol 63 (4) ◽  
pp. 931-947
Author(s):  
Teresa L. D. Hardy ◽  
Carol A. Boliek ◽  
Daniel Aalto ◽  
Justin Lewicke ◽  
Kristopher Wells ◽  
...  
Keyword(s):  
Fundamental Frequency ◽  
Sound Pressure Level ◽  
Sound Pressure ◽  
Vocal Tract ◽  
Presentation Mode ◽  
Pressure Level ◽  
Presentation Modes ◽  
Audiovisual Stimuli ◽  
Vocal Tract Resonance ◽  
Point Light

Purpose The purpose of this study was twofold: (a) to identify a set of communication-based predictors (including both acoustic and gestural variables) of masculinity–femininity ratings and (b) to explore differences in ratings between audio and audiovisual presentation modes for transgender and cisgender communicators. Method The voices and gestures of a group of cisgender men and women ( n = 10 of each) and transgender women ( n = 20) communicators were recorded while they recounted the story of a cartoon using acoustic and motion capture recording systems. A total of 17 acoustic and gestural variables were measured from these recordings. A group of observers ( n = 20) rated each communicator's masculinity–femininity based on 30- to 45-s samples of the cartoon description presented in three modes: audio, visual, and audio visual. Visual and audiovisual stimuli contained point light displays standardized for size. Ratings were made using a direct magnitude estimation scale without modulus. Communication-based predictors of masculinity–femininity ratings were identified using multiple regression, and analysis of variance was used to determine the effect of presentation mode on perceptual ratings. Results Fundamental frequency, average vowel formant, and sound pressure level were identified as significant predictors of masculinity–femininity ratings for these communicators. Communicators were rated significantly more feminine in the audio than the audiovisual mode and unreliably in the visual-only mode. Conclusions Both study purposes were met. Results support continued emphasis on fundamental frequency and vocal tract resonance in voice and communication modification training with transgender individuals and provide evidence for the potential benefit of modifying sound pressure level, especially when a masculine presentation is desired.

Case study: Theoretical calculation model and variable condition analysis research on the water-splashing noise for natural draft wet cooling towers

2020 ◽  
Vol 68 (2) ◽  
pp. 137-145
Author(s):  
Yang Zhouo ◽  
Ming Gao ◽  
Suoying He ◽  
Yuetao Shi ◽  
Fengzhong Sun
Keyword(s):  
Theoretical Model ◽  
Sound Pressure Level ◽  
Water Droplet ◽  
Water Distribution ◽  
Sound Pressure ◽  
Cooling Tower ◽  
Distribution Patterns ◽  
Calculation Model ◽  
Pressure Level ◽  
Cooling Towers

Based on the basic theory of water droplets impact noise, the generation mechanism and calculation model of the water-splashing noise for natural draft wet cooling towers were established in this study, and then by means of the custom software, the water-splashing noise was studied under different water droplet diameters and water-spraying densities as well as partition water distribution patterns conditions. Comparedwith the water-splashing noise of the field test, the average difference of the theoretical and the measured value is 0.82 dB, which validates the accuracy of the established theoretical model. The results based on theoretical model showed that, when the water droplet diameters are smaller in cooling tower, the attenuation of total sound pressure level of the water-splashing noise is greater. From 0 m to 8 m away from the cooling tower, the sound pressure level of the watersplashing noise of 3 mm and 6 mm water droplets decreases by 8.20 dB and 4.36 dB, respectively. Additionally, when the water-spraying density becomes twice of the designed value, the sound pressure level of water-splashing noise all increases by 3.01 dB for the cooling towers of 300 MW, 600 MW and 1000 MW units. Finally, under the partition water distribution patterns, the change of the sound pressure level is small. For the R s/2 and Rs/3 partition radius (Rs is the radius of water-spraying area), when the water-spraying density ratio between the outer and inner zone increases from 1 to 3, the sound pressure level of water-splashing noise increases by 0.7 dB and 0.3 dB, respectively.

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