One of the most common and important sources of noise in the residential environments are vehicles such as airplanes and subways. Trafficking of vehicles in streets and highways, psychologically, have damaging impacts on people living close to such areas. The development and expansion of the trading and industrial units is another factor that causes more and more exposure to noise.We have aimed at measuring the noises caused by vibration of subways of the Line of Karaj-Tehran-Mehrshahr and its effect on its surrounding area.To study this effect we designed a mathematical model and put the information of this subway line in the mentioned model. Then we analyzed the findings.This model demonstrated that we can control the harsh noise of the subway by reducing the speed of the train to 60Km/h in some points and increase in other parts to 130Km/h.

Background and Aim: Hearing loss results in impairment of  muscles coordination and survival essential that are engaged in motor speech timing tasks. It will negatively affect the acquisition of speech sounds. The purpose of this study was to compare the oral diadochokinesis in normal-hearing and hearing - impaired adolescents
Materials and Methods: This research was conducted on sixty-one adolescents aged 15-18 years old. Forty-six had moderately severe, severe, or profound hearing loss and fifteen were normal. The time spent to perform each oral diadochokinesis tasks was measured by speech analyzer of Dr. speech software, version four.
Results: Results indicated that hearing - impaired performed significantly slower on all speech timing tasks than their normal hearing peers except those with moderately severe hearing-impaired group. There were significant differences between profound hearing-impaired group and both other groups.
Conclusion: The results of this study point out  the motor speech problems in hearing impairment. The differences, in general, indicate that speech-timing coordination deficits are compromise with hearing loss degree.

Background and Aim: The primary energy for speech production is prepared by breathing flow. As there was no index for the maximum phonation time(MPT) to compare normal and speech disordered speakers in Iran, the purpose of this study was to establish this standard for guidance school students in Tehran. 
Materials and Methods: This cross-sectional study was performed on 576 guidance students from 1^st, 5^th, 8^th, 10^th, 15^th and 19^th educational regions. Each student made an usual inhalation and produced the /a/ for three times with the maximum strength but in a way that he/she didn&apost feel tension on his/her neck or larynx. The maximum time was recorded as the maximum phonation time.
Results: The results of this research revealed that girls`s MPT in all regions was 15.3, 16.7, and 17.16 seconds and the boys` was 15.41, 16.7 and 17.01 seconds and all students` 15.36, 16.17 and 17.08 seconds in order of their grades. There was significant difference between first and third grade mean MPT (p=0.003).
Conclusion: The result of this study indicates that, as the students age increases their MPT increase, too. Also, boys` MPT was more than girls` in first and second grades however, in third grade the girls` MPT was more.

Background and Aim: Following an early visual deprivation, the neural network involved in processing auditory spatial information undergoes a profound reorganization. In order to investigate this process, event-related potentials provide accurate information about time course neural activation as well as perception and cognitive processes. In this study, the latency and amplitude of auditory P300 were compared in sighted and early blind individuals in age range of 18-25 years old.

Methods: In this cross-sectional study, auditory P300 potential was measured in conventional oddball paradigm by using two tone burst stimuli (1000 and 2000 Hz) on 40 sighted subjects and 19 early blind subjects with mean age 20.94 years old.

Results: The mean latency of P300 in early blind subjects was significantly smaller than sighted subjects (p=0.00.( There was no significant difference in amplitude between two groups (p>0.05).

Conclusion: Reduced latency of P300 in early blind subjects in comparison to sighted subjects probably indicates the rate of automatic processing and information categorization is faster in early blind subjects because of sensory compensation. It seems that neural plasticity increases the rate of auditory processing and attention in early blind subjects.