JOURNAL OF ACOUSTICAL ENGINEERING SOCIETY OF IRAN
Year:2016 | Volume:4 | Issue:1 |Papers Count:7

The goal of a query-by-example music information retrieval system is retrieval of the target song corresponding to user-provided example from a particular dataset. The example can be a few second piece recorded from any music source such as TV or even a noisy environment e. g. gym. In this paper, a query-by-example system for music retrieval using genre recognition is proposed whose goal is to show the effect of genre recognition to achieve the accurate and rapid performance in such systems even in presence the background noise. This system includes two basic blocks: genre recognition and matching-retrieval. A binary decision tree performs the genre recognition and matching-retrieval uses two Euclidean and Kullback-Leibler (KL) distances along with a score level based decision fusion. The proposed system is evaluated on the well-known GTZAN dataset (prepared by George Tzanetakis) and by two random groups of pure and noisy queries. The results show the accuracy of 97% and 86% for two pure and noisy query groups, respectively, in retrieval time of 525 ms with Euclidean distance. These values are 97% and 82% in retrieval time of 380 ms with KL distance.

Almost, in all industries, acoustic noise is one of the harmful physical agents for human. In order to control noise, different methods are applied and acoustic absorption is one of the passive methods. For sound absorption wide range of absorbers are used. In recent year, perforated sheets are considered for sound absorption in industries and constructions. Usually perforated sheet are used with one of porous or fibrous materials, like rock fibers. Effective parameters on a flat perforated sheet are as follows; thickness, hole diameter, perforation ratio, and clearance of perforated plat from the solid back plate. In pyramidal perforated sheet a new parameter is defined, apex angle. Aim of this study was evaluation of apex angle effect on acoustic absorption coefficient. The first step of this study was construction of pyramidal geometry. Then, acoustic absorption coefficient measurments were carried out for apex angles of 24, 29, and 36 degree without any absorbing material.

The aim of the present study was to explore the effects of long term and short term of white noise exposure on spatial memory and locomotor activity of rat. For this experimental study, Fifteen Wistar male rats were divided randomly in two groups (case and control). The case group exposed to white noise (100 dB, 6hr/day, 5 day/week) for 3 weeks and the control group was kept in calm conditions. Following 2 days of the cessation of noise exposure, spatial memory and locomotor activity were evaluated by Y maze and open field tests. In order to assess the long term effects of noise, these tests were repeated and compared 21 days following the cessation of the exposure. Data showed, traveled distance and spontaneous alternation were significantly lower in the case groups (P<0. 001). furthermore, 21 days following the cessation of the exposure, locomotor activity (P<0. 020) and spontaneous alternation (P<0. 001) still were significantly lower in the case group. According to the results, exposure to noise can be an important factor in altering locomotor activity and impairment spatial memory in rats.

Noise is an unwelcome harmful factor in hospital environments. This study was conducted aiming at evaluating sound pressure levels in different parts of an educational hospital, the knowledge of that hospital’ s personnel over sound pressure level, and their attitude towards it. In this cross-sectional study, the knowledge of 29 doctors, 63 nurses, 58 clerks, and 25 orderlies was checked. All questionnaires were distributed among the personnel through simple random method, after determining the reliability and validity of them. Sound pressure level was measured by Cell 450 sound meter of the UK from the height of 150 cm, and the gathered data were analyzed by Chi-square test and SPSS software. The results of the present study indicated that, there is a meaningful relationship between job rank of an individual and sound knowledge grade of the same person (P< 0. 05), but the relationship between the job rank of a person and his attitude score was proven to be meaningless. Measurement findings after data analysis showed that, sound pressure levels and sound interference levels in all the studied parts were higher than the recommended limits in hospitals, and average sound levels of the hospital in different parts of it equaled 56. 3 decibels (dB). Gaining knowledge over sound/ noise effects, improving the personnel’ s attitude towards this subject, and regulations observance could be influential in work environments.

In this research, the sound produced due to vortices interactions of unsteady flow over three different flat plates having various leading and trailing edges configurations, is investigated applying large eddy simulation approach. Validation of the simulated non-dimensional velocity at Mach number of 0. 088 and Reynolds number of 4×105 is performed using available experimental results which showed good agreements. Also, considering the acoustic simulations, power spectral density of the sound received through two microphones (one located at 583 mm directly above and the other one located 583 mm directly below the trailing edge of the plate) showed good agreement with the experimental results. Based on the obtained results, values of sound power spectral density related to the first, second and third plates in the frequency range of 200 to 4000 Hz are approximately, 26 to 28, 27 to 32 and 28 to 57 dB, respectively.

Sound absorption behavior of A5083 open-celled foams produced by space holder method was investigated. Sound absorption coefficient of samples was investigated within the range of 500-16000 Hz, by the transfer function method. A5083 foams sound absorption was investigated by two cell sizes less than 106 and 106-250 microns. In addition, the effect of adding silicon carbide was studied with 10 vol. %. The effect of air gap depths on sound absorption coefficient was also investigated. Results indicated that A5083 foams sound absorption behavior with cell sizes less than 106 microns and 106-250 microns is very weak at most frequencies. Adding 10 vol. % of silicon carbide to A5083 foam with 106-250 microns cell sizes, improved the sound absorption properties of foams. The results of this research also indicated that using an air gap in A5083 foam with less than 106 microns cell size has no effect on sound absorption coefficient. In A5083 foam with 106-250 microns cell size and 20 mm air gap depths, at most frequencies, a better sound absorption was observed than the sample without air gap or the sample with 10 mm air gap depths.

In this paper, by development of the Roussos’ method and using the generic algorithm, the optimization of sound transmission loss for a finite rectangular simply supported panel with infinite baffle was considered. Appropriate constraints were imposed to prevent softening effect occurrence due to optimization and the discrete frequencies were chosen based upon the sound transmission class with weighting constant for optimization. Several traditional composite materials were employed for the investigation. The results indicate that, in the mass control region, the optimization of stacking sequence and optimal thickness do not effectively contribute to improvement of the transmission loss due to the close densities of composite materials. In other words, composite plate optimization made of a stiffer materials, has better transmission loss characteristics. The results also show that, the lamina thickness optimization has an important effect to improve the transmission loss but the advantage of low weight composite material is compromised by optimization.