Acoustic Performance Analysis of Impedance Compound Muffler with Aluminum Foam

2011 ◽  
Vol 279 ◽  
pp. 253-257
Author(s):  
Huai Qian Bao ◽  
Chang Tian Wang ◽  
Jun Li
Keyword(s):  
Performance Analysis ◽  
Boundary Conditions ◽  
Noise Reduction ◽  
Frequency Band ◽  
High Frequency ◽  
Aluminum Foam ◽  
Sound Field ◽  
Acoustic Properties ◽  
Acoustic Performance ◽  
The Common

The common reactive muffler has poor acoustic properties in high frequency, so aluminum foam is applied to the reactive muffler and the impendence compound muffler is designed. The acoustic performance of the muffler is analyzed; the interior sound field of the muffler is modeled and meshed in the ANSYS, then they are imported into SYSNOISE, and imposed reasonable boundary conditions to carry out the analysis of acoustic performance of the muffler. The results show that, compared to reactive muffler, the muffler with aluminum foam has a higher amount of noise reduction and a wider frequency band in middle and high frequency.

Car's Materials Acoustic Properties Test and Analysis

2013 ◽  
Vol 785-786 ◽  
pp. 1244-1247
Author(s):  
Yan Liu ◽  
Xiao Juan Zhang ◽  
Zong Cai Liu
Keyword(s):  
Noise Reduction ◽  
High Frequency ◽  
Sound Absorption ◽  
Transmission System ◽  
Acoustic Properties ◽  
Frequency Noise ◽  
Car Industry ◽  
High Frequency Noise ◽  
Urban Construction ◽  
The Impact

With the development of the car industry, the pace of the urban construction is accelerating as well. Cars have gradually entered the ordinary family. As the car noise has a big effect on the health of the passengers, as well as on the surroundings, one of the car industry key duties is the car noise reduction. By researching the materials applied to car, this article describe that PU material could reduce the impact of the engine noise on the cab efficiently; Polypropylene needle-spun felt could reduce the noise passed by chassis; PET material's sound absorption is poor in mid bass, however in high frequency it's sound absorption is good; sound absorbing sponge can reduce the low and high frequency noise; The combine sponge can reduce the noise from the tire and transmission system ; Cotton material could absorb the high frequency noise.

Theoretical End Experimental Evaluation of Perforations Effect on Sound Insulation

2017 ◽  
Author(s):  
Olga Khrystoslavenko ◽  
Raimondas Grubliauskas
Keyword(s):  
Noise Reduction ◽  
High Frequency ◽  
Sound Absorption ◽  
Low Frequency ◽  
Experimental Methods ◽  
Glass Wool ◽  
Acoustic Properties ◽  
Sound Insulation ◽  
Frequency Noise ◽  
Sound Reduction

To design a sound-absorbing panel, it is important to identify factors that affect the maximum sound absorption of low, middle and high frequency sounds. Perforation effect is very important for the noise-reducing and noiseabsorbing panels. Perforations are often used for sound reduction. Experimental data shows that the perforation is very effective to absorb low-frequency noise. In the presented study, influence of perforation coefficient of noise reduction was analyzed with theoretical and experimental methods. The experiments were conducted in noise reduction chamber using an perforated construction with glass wool filler. Sound reductions index of 15 dB indicates good acoustic properties of the panel.

scholarly journals Mechanical, Thermal, and Acoustic Properties of Aluminum Foams Impregnated with Epoxy/Graphene Oxide Nanocomposites

Metals ◽  
2019 ◽  
Vol 9 (11) ◽  
pp. 1214 ◽  
Author(s):  
Susana C. Pinto ◽  
Paula A.A.P. Marques ◽  
Matej Vesenjak ◽  
Romeu Vicente ◽  
Luís Godinho ◽  
...  
Keyword(s):  
Graphene Oxide ◽  
Epoxy Resin ◽  
Epoxy Matrix ◽  
Aluminum Foam ◽  
Acoustic Properties ◽  
Hybrid Structures ◽  
Compression Tests ◽  
Aluminum Foams ◽  
Open Cell ◽  
Acoustic Performance

Hybrid structures with epoxy embedded in open-cell aluminum foam were developed by combining open-cell aluminum foam specimens with unreinforced and reinforced epoxy resin using graphene oxide. These new hybrid structures were fabricated by infiltrating an open-cell aluminum foam specimen with pure epoxy or mixtures of epoxy and graphene oxide, completely filling the pores. The effects of graphene oxide on the mechanical, thermal, and acoustic performance of epoxy/graphene oxide-based nanocomposites are reported. Mechanical compression analysis was conducted through quasi-static uniaxial compression tests at two loading rates (0.1 mm/s and 1 mm/s). Results show that the thermal stability and the sound absorption coefficient of the hybrid structures were improved by the incorporation of the graphene oxide within the epoxy matrix. However, the incorporation of the graphene oxide into the epoxy matrix can create voids inside the epoxy resin, leading to a decrease of the compressive strength of the hybrid structures, thus no significant increase in the energy absorption capability was observed.

Research on Structure Size of Muffler to the Influence of Acoustic Properties

2013 ◽  
Vol 341-342 ◽  
pp. 366-370
Author(s):  
Jin Ku Li
Keyword(s):  
Finite Element ◽  
Noise Reduction ◽  
Volume Ratio ◽  
Element Model ◽  
Acoustic Properties ◽  
Structure Parameters ◽  
Resonant Structure ◽  
Acoustic Performance ◽  
The Relationship ◽  
The Finite Element Model

The dimention for muffler has great impact on the car engine. Based on software GAMBIT, GT-POWER,SYSNOISE,through comprehensively using finite element and boundary element method,simulating and analyzing the acoustic performance for the basic noise reduction unit,establishing the finite element model, comparing the frequency and noise reduction of different volume ratio of cavity and throat tube.Simulation analysis and experimental results show that the resonant structure parameters have a direct effect on its resonant frequency and noise reduction amount. the relationship characteristic between them is that the ratio more bigger,the requency and noise reduction amount more bigger , too.And draw the two relation formulas through calculation.

Temporary Threshold Shifts Produced by Exposure to High-Frequency Noise

1972 ◽  
Vol 15 (3) ◽  
pp. 624-631 ◽  
Author(s):  
John H. Mills ◽  
Seija A. Talo
Keyword(s):  
High Frequency ◽  
Noise Exposure ◽  
Sound Field ◽  
Acoustic Properties ◽  
Threshold Shift ◽  
Maximum Effect ◽  
Frequency Noise ◽  
Temporary Threshold Shift ◽  
Octave Band ◽  
Band Noise

Four chinchillas, monaural and trained in behavioral audiometry, were exposed for 24 days in a diffuse-sound field to an octave-band noise centered at 4.0 k Hz. The octave-band levels (OBL re 0.0002 ubar) were 57 dB for Days 1 to 6; 65 dB for Days 7 to 12; 72 dB for Days 13 to 18; and 80 dB for Days 19 to 24. At regular intervals throughout the noise exposure each animal was removed from the noise and threshold measurements were made. For each level of noise, temporary threshold shift reached an asymptote. In the frequency region of maximum effect, the relation between temporary threshold shift and the level of the noise is given by the equation TTS 4 ∞ = 1.6 (OBL-47) where TTS 4 ∞ is the temporary threshold shift at asymptote measured at a postexposure time of four minutes. These results for a noise centered at 4.0 k Hz in combination with those results for a noise centered at 0.5 k Hz suggest that bands of noise produce equal TTS 4 ∞ when the levels of the noises are equated for the acoustic properties of the external ear (including the head) and the inner ear.

Modified Earpieces and CROS for High Frequency Hearing Losses

1968 ◽  
Vol 11 (1) ◽  
pp. 204-218 ◽  
Author(s):  
Elizabeth Dodds ◽  
Earl Harford
Keyword(s):  
Hearing Loss ◽  
Hearing Aids ◽  
High Frequency ◽  
Hearing Aid ◽  
Sound Field ◽  
Intensity Level ◽  
Test Results ◽  
High Frequency Hearing Loss ◽  
Increased Sensitivity ◽  
Difficult Cases

Persons with a high frequency hearing loss are difficult cases for whom to find suitable amplification. We have experienced some success with this problem in our Hearing Clinics using a specially designed earmold with a hearing aid. Thirty-five cases with high frequency hearing losses were selected from our clinical files for analysis of test results using standard, vented, and open earpieces. A statistical analysis of test results revealed that PB scores in sound field, using an average conversational intensity level (70 dB SPL), were enhanced when utilizing any one of the three earmolds. This result was due undoubtedly to increased sensitivity provided by the hearing aid. Only the open earmold used with a CROS hearing aid resulted in a significant improvement in discrimination when compared with the group’s unaided PB score under earphones or when comparing inter-earmold scores. These findings suggest that the inclusion of the open earmold with a CROS aid in the audiologist’s armamentarium should increase his flexibility in selecting hearing aids for persons with a high frequency hearing loss.

scholarly journals Virtual Sound Field of the Roman Theatre of Malaca

Acoustics ◽  
2021 ◽  
Vol 3 (1) ◽  
pp. 78-96
Author(s):  
Javier Alayón ◽  
Sara Girón ◽  
José A. Romero-Odero ◽  
Francisco J. Nieves
Keyword(s):  
3D Model ◽  
Sound Field ◽  
Acoustic Properties ◽  
Archaeological Remains ◽  
Roman Emperor ◽  
Stone Surface ◽  
Process Adjustment ◽  
Decay Parameters ◽  
The Hill ◽  
The City

In Hispania (present-day Spain and Portugal), there are 25 structures documented of classical Roman open-air theatres, of which 10 are in the south, in the Roman Baetica (Andalusia). The Baetica embraced the progress of urbanisation in the time of the Roman emperor Augustus, where theatres, built in stone, were the foci of entertainment, performance, and propaganda of the empire. The Roman theatre in Malaga presents the archaeological remains of the main vestige of the Roman Malaca. It is located in the historical centre of the city, at the foot of the hill of the Muslim Alcazaba and was discovered in 1952. It is a medium-sized theatre whose design corresponds to a mixed construction that combines making use of the hillside for the terraces, in the manner of Greek theatres, with a major construction where rock is non-existent, thereby creating the necessary space for the stands. In this paper, the production process, adjustment, and validation of the 3D model of the theatre are analysed for the creation of a numerical predictive model of its sound field. Acoustic properties of the venue are examined and the effect of the Muslim Alcazaba and the hillside on the various acoustic descriptors is analysed. The results highlight the influence of this large stone surface mainly on the time decay parameters.

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