جستجوی مقالات مرتبط با کلیدواژه "تحلیل اکوستیکی" در نشریات گروه "پزشکی"

Town Board Stations (TBS) installations with increment in gas consumption and overloading are one of the sources of noise pollution. The present study was aimed to assess and provide an occupational noise exposure control plan in TBS.

Area noise measurement and frequency analysis was performed according to ISO 9612(2009). After the determination of the range of sound pressure level, predominant source of noise was identified .In addition, dosimetry was conducted to determine the personal exposure during a work shift. In the next step,acoustical analysis of TBS of the sample,construction was conducted based on acoustical absorbance properties. Installation of absorbent materials was recommended and the efficiency of the interventions was assessed.

sound pressure level was in the range of 68.64 to 95.30 dB(A) in TBS. The minimum and maximum effective sound absorption of internal surfaces were 3.61 and 27.64 Sabine m2,respectively.The average noise exposure dose for maintenance workers was 121%.After installation of absorbent materials on ceiling and walls, the effective sound absorption of the surfaces was improved to a maximum of 210.35 Sabine m2 and a minimum of 40.35 Sabine m2. The noise reduction prediction for these control plan will be 8.69 -11.6 dB(A).

The main reason of noise in the TBS was the passage and turbulence of gas flow in the mechanical unit, and reflective surfaces in constructions enclosing the installations. The control strategy, including the use of absorbent materials on ceiling and walls, was determined to reduce the sound pressure level to occupational exposure limit.

In the steel industry, air blowers used to supply compressed air are considered as sources of annoying noise. This study aims to design acoustic room chamber in order to noise control of air blower. Measuring of the noise level along with frequency analysis were performed by using sound level meter model of CASELLA-Cell.450. Dosimetery in order to worker exposure was performed using the dosimeter model TES-1345. Linear sound power level of machine was calculated based on ISO 3746. Distribution of noise emission of the source was shown in form of workroom noise maps using Surfer software. Acoustic analysis of workroom was performed based on sound absorption characteristic of internal surfaces. In order to noise control, an enclosure along with condensed sandwich panels for blower was designed and finally, the effect of this intervention was estimated. The results showed the total sound pressure level of the air blower was 95.4dB (Lin) in which the dominant frequency was 2000 Hz. Moreover, sound power level of the air blower in the dominant frequency was 102.94dB (Lin). The effective absorption surface of workroom was estimated equal to 0.082 and the average occupational noise exposure level based on noise dose was equal to 230%. The designed enclosure along with the steel and fiberglass as a primary insulation layer and punched sheet by steel layer as absorption sound on internal surfaces, actual transmission loss in the dominant frequency, by taking 0.001 opening, was estimated 30dB. gearbox and compressor was the main cause air blower noise that is created Because of the Spiral gearing wheels spinning rotor gearbox parts and the interaction between the rotary and fixed blades move air through the compressor is caused. Enclosure design noise dose received by worker reduced to less than 20 percent. Keywords: module design, air blower, noise control, acrostic analysis, steel industry.

In the steel industry, coke-fueled furnaces are used for smelting iron ore to produce cast iron are considered as sources of annoying noise.This study aims to evaluate the noise pollution blast furnace and sound source characteristics in order to present noise control measures in the steel industry.

Measurement of noise level and its frequency analysis was performed using sound level meter model of CASELLA-Cell.450. Dosimetery in order to worker exposure was performed using the dosimeter model TES-1345.Distribution of noise level in the furnace area in form of noise map was provided using Surfer software. In addition, acoustic analysis of control and furnace workers rest rooms was performed in view point of and insulation.Redesign of door and window of control room and reform of worker's rest room were proposed and the efficiency of these interventions was estimated.

The total sound pressure level in the furnace workroom was 90.3dB(L) and the dominant frequency was 2000Hz. Sound transmission loss of the wall dividing the control room and rest room workers furnace 10.3 and 4.23dB, respectively. The average of noise dose in furnace worker was 240%. And sound transmission loss of the new The performance of the proposed control schemes based on sound insulation of rooms was estimated equal to 30dB.

The main cause of noise pollution caused by turbulent air flow in the air ducts furnace. The acoustic Shelter was designed for standard control room and rest as the most effective method of controlling worker's exposure to noise. Accordingly, the workers received a noise dose of less than 100% can reduce.

Parkinson’s disease (PD) is a progressive neurological disorder resulting from significant decrease of dopamine in the brain. The main and most common symptom of speech disorder associated with Parkinson’s disease, which is kind of dysarthria, is reduction in speech intelligibility. Since this disorder represents damages to acoustic aspects, researchers are attracted to study the relationship between these two disorders. In this study, we assessed the comparison of speech vowels between normal people and patients with Parkinson’s disease. In this cross-sectional study, 18 voice samples of patients with Parkinson’s disease and the same number of samples from normal people in a voiceless environment were recorded and analyzed by Praat software. Data analysis was performed by independent samples and Mann-Whitney tests. All variables investigated in two groups showed significant differences. In adults with Parkinson’s disease, F1-F0 in low vowels showed a considerable reduction in respect to normal people (p<0.001). In addition, F2-F1 in high vowels represented a significant decrease in these patients (p<0.05). The results indicate that Parkinson’s disease affects formant frequency in patients compared with normal people. Reduction in speech intelligibility can be accurately measured using acoustic procedure.

In the steel industry،air blowers used to supply compressed air are considered as sources of annoying noise. This study aims to acoustics analysis of theairblower workroomand sound source characteristics in order to present noise controlmeasuresinthe steel industry. Measurement of noiselevel and its frequency analysis was performed usingsound levelmetermodelof CASELLA-Cell. 450. Distribution of noise level in the investigated workroom in form of noise map was provided using Surfer software. In addition، acoustic analysis of workroom and control room was performed in view point of soundabsorption andinsulation. Redesignofdoor and window of controlroom and installation of soundabsorbing materialson theceiling of the workroom were proposed and the efficiency of these interventionswasestimated. The totalsound pressurelevelin the blower workroom was 95. 4 dB (L) and the dominant frequency was 2000Hz. Sound pressure level inside the room control was 80. 1dB (A). The average absorption coefficient and reverberation time in the blower workroom was estimated equal to 0. 082 Sab. m2 and 3. 9 seconds respectively. These value in control room was 0. 04 Sab. m2 and 3/4 seconds respectively. In control room، sound transmission loss between the two parts of the wall dividing was 13. 7 dB (A). The average of noise dose in blower operators was 230%. With the installation of sound absorber on ceiling of workroom، average of absorption coefficient can increase to 0. 33 Sab. m2 and sound transmission loss of the new designed door and window was estimated equal to 20dB. The main cause of noise leakage in the control room was insufficient insulation properties of door and windows. By replacing the door and window and installation of sound absorbing on ceiling of workroom، the noise dose can reduce to 49. 6%. New Improved door and window of control room can reduce noise dose to 69. 65% solely.

The feedback provided by auditory apparatus equips normal hearing people with an important controlling mechanism over the speech production processes. The speech of hearing-impaired children is both perceptually and acoustically abnormal. This study tried to compare the formant frequencies of three long vowels in Persian-speaking children who used cochlear implant and those who were of normal-hearing ability.

20 Cochlear-implanted (CI) children and 20 normal-hearing children with the age ranged from 5 to 10 years participated in this study. All participants were native speakers of Persian who were asked to produce prolonged vowels /i/، /u/ and /ɒ/. The averaged F1 and F2 were calculated for each examinee using Praat software (version 5. 3. 13). Independent t test was conducted to examine the possible differences thatF1 and F2 values and F2 to F1 ratios may have in the two groups.

Study results revealed a relative increase in the F1 mean values of all the three vowels produced by CI children. This difference was، however، significant only in the first formant of vowel /i/ (P = 0. 011). The mean values of F2/F1 ratio for vowel /i/ showed a statistically significant difference between the two groups (P = 0. 01).

F1 formants are increased in cochlear-implant children. This condition might be due to a process in which the lack of auditory feedback is compensated by the proprioceptive feedback that is provided through the exaggerated articulation. The changes in F1 and F2 imply a reduced vowel space، in other words، vowel space is slightly centralized in CI children.