“The pilot study shows deterioration of hearing thresholds in tested frequencies in both ears after a long stay (one year) in high altitude area,” the authors said. Titled, “A pilot study comparing hearing thresholds of soldiers at induction and after completion of one year in high altitude area,” the research undertaken by four military officers and an executive director in the Ministry of Health and Family Welfare, has been published in the latest issue of Medical Journal Armed Forces India. “These results are found to be statistically significant for all frequencies,” the study observed. Statistical comparison of the two sets of thresholds for air conduction revealed worsening of hearing in both ears, though there was some variation in the mean quantum of deterioration between right and left years. The hearing thresholds of 433 soldiers posted in high altitude areas were recorded using pure tone audiometry with different frequencies at the time of induction and then again after a year’s stay in high altitude. Office JL Taman Bendungan Asahan 5 Jakarta Indonesia 10210Ĭopyright © 2009, Children Speech Clinic Information Education Network.Even as the unprecedented concentration of troops along the Himalayan border with China continues, a new study by military medical experts has highlighted the adverse impact on the hearing ability of soldiers who are deployed in high altitude areas over a prolonged period.Īfter observing significant variation in the threshold levels of hearing before and after induction in high altitude areas, the study has recommended greater focus on this area which has so far remained on the sidelines of research on the effects that high altitude has on the human body. KEY WORDS: orofacial movement, muscle activity, speech rate, intensity In contrast, rate control appears to be more strongly related to the temporal characteristics of neural input than activation level. For intensity control, it is suggested that converging neural input to orofacial motoneurons varies monotonically with movement distance and speed. Across the rate conditions, EMG level was negatively correlated with movement duration in all participants, while greater interparticipant variability was noted for correlations relating EMG to speed and distance. Across the intensity conditions, EMG level was positively correlated with movement speed and distance in all participants. Average EMG levels for all 4 muscles were well correlated with specific parameters of movement. Intensity variations ranged from –10 dB to +8 dB. All participants produced linear changes in percent utterance duration relative to the auditory targets for speech rate variation. Two-dimensional displacements of the lower lip and jaw in the midsagittal plane were recorded with an electromagnetic system. Surface electromyographic (EMG) recordings were obtained with electrodes positioned to sample primarily the mentalis, depressor labii inferior, anterior belly of the digastric, and masseter muscles. Recordings were obtained on orofacial movement, muscle activity, and the acoustic signal in 3 normal speakers as they repeated a simple test utterance with targeted speech rates varying from 60% to 160% of their habitual rate and at targeted vocal intensities of –6 dB and +6 dB relative to their habitual intensity. The present study involved a correlation analysis relating average lower-lip and jaw-muscle activity to lip and jaw movement distance, speed, and duration. Understanding how orofacial muscle activity and movement covary across changes in speech rate and intensity has implications for the neural control of speech production and the use of clinical procedures that manipulate speech prosody. Journal of Speech, Language, and Hearing Research Vol.46 1387-1400 December 2003ġ Western Michigan University, Kalamazoo, and Army Audiology and Speech Center, Walter Reed Army Medical Center, Washington, DC