Open Journal of Acoustics
ISSN / EISSN : 21625786 / 21625794
Current Publisher: Scientific Research Publishing, Inc, (10.4236)
Total articles ≅ 121
Latest articles in this journal
Open Journal of Acoustics, Volume 9, pp 39-47; doi:10.4236/oja.2019.93004
Abstract:Coir fibre is extracted from the husk of coconut and is used in products such as floor mats, door mats, brushes and mattresses and in many applications. Here coir fibres are used to make particle boards of densities 300, 400 and 500 kg/m3 using UF resin to determine its efficiency for interior applications like acoustic and thermal properties and also tested for Indian standard 3129. Noise Reduction Coefficient (NRC) of all the boards decreases with an increase in density. Maximum sound absorption coefficient for all three densities was found in the frequency range of 2500 to 30,000 Hz. Among three densities, 300 kg/m3 board shows the maximum absorption coefficient at frequency 3000 Hz. The thermal conductivity results of all three densities boards increase with an increase in density. Modulus of Rupture for all three densities were meeting the requirement of standard. Results reveal that particle board manufactured from coir fibre can be used for acoustic and thermal insulation applications.
Open Journal of Acoustics, Volume 9, pp 1-12; doi:10.4236/oja.2019.91001
Abstract:Propagation of Love waves in a transversely isotropic poroelastic layer bounded between two compressible viscous liquids is presented. The equations of motion in a transversely isotropic poroelastic solid are formulated in the framework of Biot’s theory. A closed-form solution for the propagation of Love waves is obtained in a transversely isotropic poroelastic layer. The complex frequency equation for phase velocity and attenuation of Love waves is derived for a transversely isotropic poroelastic layer when it is bounded between two viscous liquids and the results are compared with that of the poroelastic layer. The effect of viscous liquids on the propagation of Love waves is discussed. It is observed that the presence of viscous liquids decreases phase velocity in both transversely isotropic poroelastic layer and poroelastic layer. Results related to the case without viscous liquids have been compared with some of the earlier results and comparison shows good agreement.
Open Journal of Acoustics, Volume 9, pp 26-38; doi:10.4236/oja.2019.92003
Abstract:In this study, noise pollution assessments were performed along Marechal Deodoro Avenue and Batel Avenue, which are two major thoroughfares in the city of Curitiba, Brazil. Eleven points were evaluated at Batel Avenue and 16 points at Marechal Deodoro Avenue. The results of the noise level measurements and the calculation of noise maps indicated that both thoroughfares are acoustically polluted. The simulated and measured noise levels, in the 27 evaluated points, exceed the limits established by law 10,625 of the city of Curitiba, which establishes acceptable levels for the comfort of the population in the external environment. With regard to the traffic composition in the areas under study, the vehicle flow was found to consist mostly of light vehicles, representing 88% of the total flow along Batel Avenue and 85% on Marshal Deodoro Street. Based on the noise maps and measured noise levels, it was found that the entire length of Marshal Deodoro Avenue and Batel Avenue are strongly affected by street noise, which is readily explained by the constant traffic, high vehicle flow (number of vehicles/hour) and high vehicle speed at some points of these thoroughfares.
Open Journal of Acoustics, Volume 9, pp 13-25; doi:10.4236/oja.2019.92002
Abstract:It has been hypothesized that objective assessment for building acoustic conditions only may not always be representative of the users’ perception in occupied indoor spaces. This study objectively and subjectively examined indoor acoustic condition in rooms within students’ hostels in Obafemi Awolowo University, Nigeria. The objective assessment considered the physical measurement of sound pressure level in the rooms in relation to the rooms’ physical characteristics like window to external wall area and window to floor area ratios. The subjective assessment considered the occupants’ perception of the acoustic condition in the rooms in relation to their personal characteristics like age, gender, body mass index, metabolic rate, and body skin area. The sound pressure level was measured in each of the randomly selected 44 rooms at 15 minute intervals between 7 hours and 19 hours daily through a period of eight weeks. The measurement was done with High Accuracy Digital Sound Noise Level Data Loggers placed at work plane at the centre of the rooms. The geometry of the rooms was documented through physical measurements. All the occupants of the selected rooms as well as the two adjoining rooms, amounting to 696 respondents, were purposively selected to fill a questionnaire regarding activities carried out in the rooms, the frequency of fenestration opening, the personal characteristics of the occupants and the rooms’ occupancy ratio. This study established a strong correlation between the objective and subjective assessments of the acoustic condition in the spaces. Moreover, out of all the occupants’ personal characteristics considered, it was the age that has a relationship with the occupants’ perception of the acoustic condition that is closest to significant level.The relationship between their perception and measured sound pressure level was slightly more pronounced among the male gender than the female with correlation coefficients of 0.115 and 0.096 respectively. This study concluded that none of the considered occupants’ personal characteristics can effectively predict their response to indoor acoustic condition in the spaces.
Open Journal of Acoustics, Volume 8, pp 23-35; doi:10.4236/oja.2018.82003
Open Journal of Acoustics, Volume 8, pp 13-22; doi:10.4236/oja.2018.82002
Open Journal of Acoustics, Volume 8, pp 61-69; doi:10.4236/oja.2018.84006
Open Journal of Acoustics, Volume 8, pp 52-60; doi:10.4236/oja.2018.83005
Abstract:An extra-cochlear stimulation system has been investigated as a less invasive alternative to conventional cochlear implant; however, the system is used primarily as a speech-reading aid. The purpose of this study was to develop a speech encoding scheme for the extra-cochlear stimulation system to convey intelligible speech. A click-modulated speech sound (CMS) was created as a simulation of the extra-cochlear stimulation system. The CMS is a repetitive click with a repetition rate similar to the formant frequency transition of an original sound. Seven native Japanese speakers with normal hearing participated in the experiment. After listening to the CMS, synthesized from low familiarity Japanese words, the subjects reported their perceptions. The results showed that the rates of correctly identified vowels and consonants were significantly higher than those of the control stimulus, suggesting that the CMS can generate at least partially intelligible vowel and consonant perceptions. In all, the speech encoding scheme could be applied to the extra-cochlear stimulation system to restore speech perception.
Open Journal of Acoustics, Volume 8, pp 37-51; doi:10.4236/oja.2018.83004
Open Journal of Acoustics, Volume 8, pp 1-11; doi:10.4236/oja.2018.81001
Abstract:The availability of ideal conditions like anechoic chamber to characterize some sound parameters, like sound intensity and sound power necessities the determination of free field and cut off frequency measurements. In this article, full experiment was executed at Wayne State University (Detroit-Michigan), to determine the cut off frequency in all directions; the obtained results showed that the free field can be determined for a specified space. So other tests can take place in this space avoiding regions where reflections and consequently noise can be found. Upon these results tests related to noise abatement in vehicles can be done in such environment.