IMPROVEMENT OF SOUND INSULATION IN LOW FREQUENCY RANGE ON HOLLOW METAL DOOR(Environmental Engineering)

In order to solve the problem of strong penetration and difficult attenuation of low-frequency sound wave in traditional materials, several three-dimensional acoustic black hole superstructures are designed. First of all, multi-stage acoustic black holes are designed. It is found that their sound insulation coefficient is about 0.9 in the frequency range of 50–1600 Hz when the ration of the outlet tip diameter to the inlet diameter is [Formula: see text]. Then, the acoustic black hole thin and light superstructure was designed by embedding many acoustic black hole units in an array on the 10 mm thick plate. The sound insulation coefficient of two samples embedded 81 or 144 acoustic black holes is above 0.96 in the frequency range of 50–1600 Hz. To facilitate processing and engineering applications, we designed acoustic black hole wedge-shaped plate superstructures, and found that the average sound insulation of these acoustic black hole superstructures is 30 dB in the frequency range of 50–1600 Hz. These superstructures will be widely used in anechoic rooms, factories and aviation.

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AIRBORNE SOUND INSULATION IMPROVEMENT ON MASONRY PARTITIONS USING ADDITIONAL PLASTERBOARD LAYERS

Engineering Structures and Technologies ◽

10.3846/skt.2011.04 ◽

2011 ◽

Vol 3 (1) ◽

pp. 33-40 ◽

Cited By ~ 2

Author(s):

Marius Mickaitis ◽

Aleksandras Jagniatinskis ◽

Boris Fiks

Keyword(s):

Theoretical Calculations ◽

Low Frequency ◽

Masonry Wall ◽

In Situ Measurements ◽

Sound Insulation ◽

Frequency Range ◽

Airborne Sound ◽

Sound Reduction ◽

Reduction Index

For the purposes of accumulating knowledge of how to comply with requirements for new buildings of obligatory sound class C or enhanced acoustic comfort sound classes A and B (Lithuanian Building Technical regulations STR 2.01.07:2003), the article discusses improvement on airborne sound insulation of partitions between dwellings using additional plasterboard layers. The results of an empirical approach were obtained performing in situ measurements of the partitions of masonry from silicate blocks and expanded-clay concrete blocks. Theoretical calculations without the evaluation of flanking paths are added. The paper looks at the peculiarities of in situ measurement methods and the estimation of the limiting uncertainty of the sound reduction index. It is showed that the values of the in situ measurements of the airborne sound reduction index in accordance with requirements EN ISO 140 and EN ISO 717 series for rooms having volume higher than 50 m3 varies depending on frequency range. It has been stated, that improvement on the weighed airborne sound reduction index in the frequency range from 100 Hz to 3150 Hz depends on the properties of additional layers and on the characteristics of the main constructions. Resonance in the low frequency range arising due to additional layers may reduce the weighed airborne sound reduction index defined in the frequency range from 50 Hz to 3150 Hz. This fact must be taken into account when designing improvement on masonry wall insulation using an additional layer in dwellings.

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On the use of finite-element methods to minimize uncertainties in airborne sound insulation measurements in the low frequency range

The Journal of the Acoustical Society of America ◽

10.1121/1.4987683 ◽

2017 ◽

Vol 141 (5) ◽

pp. 3596-3596

Author(s):

Francesco Martellotta ◽

Ubaldo Ayr ◽

Gianluca Rospi

Keyword(s):

Finite Element ◽

Finite Element Methods ◽

Low Frequency ◽

Sound Insulation ◽

Frequency Range ◽

Airborne Sound

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Applications for Silica-Based Aerogel Products on an Industrial Scale

MRS Proceedings ◽

10.1557/proc-521-179 ◽

1998 ◽

Vol 521 ◽

Author(s):

M. Schmidt ◽

F. Schwertfeger

Keyword(s):

Silica Aerogel ◽

Manufacturing Process ◽

Raw Materials ◽

Ambient Pressure ◽

Low Frequency ◽

Industrial Scale ◽

Sound Insulation ◽

Frequency Range ◽

Binding Material ◽

The Right

ABSTRACTAerogels, nanoporous lightweight materials, were discovered more than 60 years ago. The supercritical manufacturing process and expensive raw materials typically used to produce aerogels prohibited commercialization on an industrial scale. Recently a commercially attractive ambient pressure production process was developed which will allow broader commercialization of silica-aerogel products.Some aerogel products for insulation applications and their preparation are described. Sound insulation properties including a remarkable absorption in the difficult low frequency range was found. In the case of insulation plates performance depends on binder and can be positively influenced by choosing the right binding material.

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Prediction of the sound reduction index of clay hollow brick walls

Building Acoustics ◽

10.1177/1351010x20903144 ◽

2020 ◽

Vol 27 (2) ◽

pp. 155-168 ◽

Cited By ~ 3

Author(s):

Nicola Granzotto ◽

Antonino Di Bella ◽

Edoardo Alessio Piana

Keyword(s):

High Frequency ◽

Low Frequency ◽

Sound Insulation ◽

Frequency Range ◽

Proposed Model ◽

Different Types ◽

Classic Approach ◽

Hollow Brick ◽

Sound Reduction ◽

Reduction Index

Clay hollow brick walls are still popular in building industry, but the prediction of their sound insulation properties is not straightforward due to their inhomogeneous and anisotropic characteristics. In this article, a classic approach has been used to determine the sound transmission coefficient of brick walls, assuming an orthotropic behaviour and deriving the mechanical and dynamic characteristics from datasheet information. Different types of walls with horizontal and vertical mortar joints have been analysed. Experimental measurements of the sound reduction index carried out according to ISO 10140-2 standard have been performed, and the resulting values are compared with the predictions in the proposed model. It was found that the sound reduction index can be fairly predicted in the low-frequency range and it is correctly predicted in the mass law region, whereas in the high-frequency range the inner block structure is responsible for a loss of performance which is difficult to predict with the analytical methods.

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Experimental and numerical research on the underwater sound radiation of floating structures with covering layers

Proceedings of the Institution of Mechanical Engineers Part C Journal of Mechanical Engineering Science ◽

10.1177/0954406214536719 ◽

2014 ◽

Vol 229 (3) ◽

pp. 447-464 ◽

Cited By ~ 2

Author(s):

Dawei Zhu ◽

Xiuchang Huang ◽

Yu wang ◽

Feng Xiao ◽

Hongxing Hua

Keyword(s):

Low Frequency ◽

Sound Radiation ◽

Numerical Results ◽

Homogenization Theory ◽

Sound Insulation ◽

Underwater Sound ◽

Frequency Range ◽

Floating Structures ◽

Covering Layer ◽

Element Method

This paper presents experimental and numerical investigation into the underwater sound radiation characteristics of a free-floating stiffened metal box covered with three different kinds of covering layers and subjected to mechanical excitation. One box is bare while the other three are, respectively, covered with solid covering layers, chiral covering layers, and chiral covering layers filled with expanded polystyrene (EPS) foams. The equivalent elastic modulus of chiral covering layer is obtained by the homogenization theory. The finite element method and boundary element method are used to calculate the underwater sound pressure. The measured and numerical results are illustrated and the sound insulation mechanisms of three covering layers are discussed. The measured results agree with the numerical results well. The covering layers can obviously reduce the underwater sound radiation of floating structures. Compared with the solid covering layer, the chiral covering layer is less effective in suppressing the sound radiation in the low-frequency range but more effective in the medium- and high-frequency range. The chiral covering layer filled with EPS foams shows the best performance, which is more effective in suppressing the sound radiation both in the low-frequency range and in the medium-frequency range. The EPS foams have a high contribution to the added damping of the chiral covering layer.

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Study of Sound Insulation of Control Cabins in Industry in the Low Frequency Range

Journal of Low Frequency Noise Vibration and Active Control ◽

10.1177/026309239201100202 ◽

1992 ◽

Vol 11 (2) ◽

pp. 42-46

Author(s):

Anna Kaczmarska ◽

Danuta Augustyriska

Keyword(s):

Noise Reduction ◽

Sound Pressure ◽

Low Frequency ◽

Machine Building ◽

Sound Insulation ◽

Frequency Noise ◽

Low Frequency Noise ◽

Frequency Range ◽

Sound Pressure Levels ◽

Lower Frequencies

The number of control cabins installed in industry has increased considerably during the last few years. Most cabins installed nowadays show a satisfactory noise reduction in the frequency range above 500 Hz. The effect of noise damping however shows a gradual decrease for lower frequencies. The present paper is a description of the distribution of low frequency noise in different types of control cabins installed in typical low frequency noise environments in steel plants and the machine building industry. Measurements were made in 20 control cabins, constructed of metal and stone Measurements of sound pressure levels in octave bands were made inside and outside the cabins. The sound pressure level in octave bands in the low frequency range (4–31.5 Hz) inside the cabins was high and varied between 60–108 dB. This is probably due to the insufficient noise reduction for lower frequencies. In some control cabins there was an increased level of low frequency noise inside the cabin compared to the outside. In these control cabins sound pressure levels exceed the admissible values according to Polish standards. The increase of noise level within the low frequency range is considered to be based on resonances.

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Motor Vehicle Exterior Sound Quality Improvement for Indoors

Noise Control and Acoustics ◽

10.1115/imece2006-14041 ◽

2006 ◽

Author(s):

Masao Ishihama ◽

Hiromitsu Sakurai

Keyword(s):

Engine Speed ◽

Motor Vehicle ◽

Traffic Noise ◽

Low Frequency ◽

Sound Quality ◽

Sound Insulation ◽

Frequency Range ◽

Sound Environment ◽

Frequency Components ◽

Driving Conditions

The objectives of this study are these three items. 1) To find better indices than dB(A) for representing annoyances caused by motor vehicle traffic noise along highways. 2) To find the frequency range of motor vehicle exterior noise that should primarily be controlled to achieve better indoor sound environment along highways. 3) To find suitable vehicle driving conditions for evaluating indoor sound environment. To obtain the desired results psycho-acoustic experiments were conducted. Firstly, sound samples were collected with microphones placed at such locations as on a sidewalk, in front of a small house and at the center of a room inside of the house. The number of test vehicles was fifteen, consisting of six motorcycles and nine passenger cars. The driving conditions were full acceleration and mild acceleration usually found in normal traffic flow. Secondly, semantic differentiation method was used. Ten pairs of adjectives were used to scale the impressions of each sound sample. Finally, physical characters of the sound samples and their subjective evaluations were compared. The results were obtained as follows. 1) Six sound samples got more uncomfortable impression at indoors. These sound samples were collected by vehicles with sport-type mufflers. 2) The samples that indoor sound quality is degraded than outdoor contain high power in low frequency range below 200 Hz. These low frequency components penetrate through the housing walls more easily than higher frequency components. 3) The degradation of comfort impression was found in mild acceleration conditions. The low frequency components of sound samples for mild acceleration are larger than those for full acceleration. Though the throttle is not fully open in mild acceleration, low engine speed generates low frequency components, and eventually increased indoor sound power in the frequency range. The conclusions drawn from these results are, 1) Indoor sound samples should be included for evaluating sound environment along highways. 2) Mild acceleration is a better driving condition for evaluating indoor sound environment along highways. In this condition, very low engine speed causes low frequency component emission that penetrate into housing more than in heavy accelerating conditions. 3) Engine exhaust systems that emit very loud low-frequency components should be focused upon in regulating traffic noise. 4) Extensive collection and analysis of housing sound insulation, absorption and resonance data along highways are necessary for further investigations. 5) Better psycho-acoustic experiment methods should be developed for investigating sound context effects on panelists.

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Evaluation of Special Hearing Aids for Deaf Children

Journal of Speech and Hearing Disorders ◽

10.1044/jshd.3604.527 ◽

1971 ◽

Vol 36 (4) ◽

pp. 527-537 ◽

Cited By ~ 1

Author(s):

Norman P. Erber

Keyword(s):

Hearing Aids ◽

High Frequency ◽

Hearing Aid ◽

Low Frequency ◽

Acoustic Stimulation ◽

Deaf Children ◽

Frequency Range ◽

Frequency Limit ◽

Unpublished Studies ◽

Published Research

Two types of special hearing aid have been developed recently to improve the reception of speech by profoundly deaf children. In a different way, each special system provides greater low-frequency acoustic stimulation to deaf ears than does a conventional hearing aid. One of the devices extends the low-frequency limit of amplification; the other shifts high-frequency energy to a lower frequency range. In general, previous evaluations of these special hearing aids have obtained inconsistent or inconclusive results. This paper reviews most of the published research on the use of special hearing aids by deaf children, summarizes several unpublished studies, and suggests a set of guidelines for future evaluations of special and conventional amplification systems.

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Dynamic Damping and Stiffness Characteristics of the Rolling Tire

Tire Science and Technology ◽

10.2346/1.2135243 ◽

2001 ◽

Vol 29 (4) ◽

pp. 258-268 ◽

Cited By ~ 12

Author(s):

G. Jianmin ◽

R. Gall ◽

W. Zuomin

Keyword(s):

Dynamic Behavior ◽

Variable Parameter ◽

Low Frequency ◽

Vertical Load ◽

Frequency Range ◽

Inflation Pressure ◽

Vehicle Simulation ◽

Dynamic Damping ◽

Speed Range ◽

Stiffness Characteristics

Abstract A variable parameter model to study dynamic tire responses is presented. A modified device to measure terrain roughness is used to measure dynamic damping and stiffness characteristics of rolling tires. The device was used to examine the dynamic behavior of a tire in the speed range from 0 to 10 km/h. The inflation pressure during the tests was adjusted to 160, 240, and 320 kPa. The vertical load was 5.2 kN. The results indicate that the damping and stiffness decrease with velocity. Regression formulas for the non-linear experimental damping and stiffness are obtained. These results can be used as input parameters for vehicle simulation to evaluate the vehicle's driving and comfort performance in the medium-low frequency range (0–100 Hz). This way it can be important for tire design and the forecasting of the dynamic behavior of tires.

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