Investigating the effects of noise exposure on intensification of diabetes mellitus, serum glucose, cortisol level and body weight of the male mice

Noise is considered as one of the harmful factors at industrial environments. It affects human health in different aspects including harmful influences on auditory, vision, neurological and psychiatric systems, hormones, physiological and mental systems. Paying attention to the importance of hormonal effects on human body seems to possess crucial importance. The aim of the present study is to investigate the effects of noise exposure on variation of serum levels of glucose and cortisol at Syrian adult male mouse. 36 Syrian male adult mice were randomly categorized into two experiment and control groups. Garlic powder was added to the mice pelleted food meal (equal to 1% of their daily diet) to study its effect on the cortisol and glucose serum levels. The mice pelleted food contains starch, glucose, isolated soya protein, etc., which are the rich resources of A, C, B1, B2 and B6 vitamins. Streptozotocin (60mg/kg) was injected to the mice at experiment group which were under noise exposure with intensity of 90dB in frequency range of 700-5700Hz. Noise were generated using CoolEdit software and distributed to the fabricated box for 30 days (8h/d).  Fasting cortisol and glucose serum levels were measured for mice of both groups 24h after finishing the exposure period. Results indicated that the glucose serum level in non-diabetic and diabetic subjects under noise exposure had significant difference (p<0.002) with the subjects at control group. Also, cortisol level in non-diabetic and diabetic subjects under noise exposure indicated significant difference (p<0.002) with the subjects at control group. Exposure to noise with intensity of 90dB at frequency range of 700-5700Hz increases the glucose and cortisol serum levels

Acoustic properties of 3D printed bio-degradable micro-perforated panels made of Corkwood Fiber-Reinforced composites

Introduction: Micro perforated panel (MPP) absorbents promise the next generation of sound absorbers as they have significant advantages over other porous adsorbents. In this study, we will investigate the acoustic performance of MPP absorbents made of biodegradable polylactic acid composite reinforced with natural corkwood fibers (PLA/Corkwood) by 3D printing technology. Material and Methods: First, the effective dimensional characteristics of the parameters were determined, then, all of the samples were fabricated by the Zortrax M200 3D-Printer using the FDM method. The normal incidence sound absorption coefficient of the samples was measured using an acoustic impedance tube according to ISO 10534-2 in the frequency range of 64 to 1600 Hz. Then the effect of four geometric parameters, including hole diameter, panel thickness, perforation ratio, and air gap depth, on the absorption coefficient was studied. Results: The findings show that the SL-MPP 12 absorbent has the highest average sound absorption coefficient (SACA) with a value of 0.28, so that at a frequency of 804 Hz it has the highest sound absorption equal to 0.91. The parametric study found that as the hole diameter increased, the values of peak adsorption and average absorption coefficient were decreased. Increasing the MPP thickness causes the absorption peak to move towards the lower frequency range. Decreasing the perforation ratio increases the peak absorption values and the average sound absorption, and the frequency with the highest absorption also moves towards the higher frequency range. The resonant frequency also depends on the depth of the air gap behind the screen. Changes in air gap depth from 30 mm to 70 mm reduced the resonant frequency by more than 35%. Conclusion: Using 3D printing technology, sustainable MPP can be fabricated with more quality and in less time than traditional methods such as mixing and heat pressing

Protective Effects of α-Tocopherol on ABR Threshold Shift in Rabbits Exposed to Noise and Carbon Monoxide

Abstract Noise induced hearing loss (NIHL) is one of the most important occupational disease worldwide. NIHL has been found potentiate by simultaneous carbon monoxide (CO) exposure. Free radicals have been implicated in cochlear damage resulted from the exposure to noise and due to the CO hypoxia. This study examined whether α-tocopherol administration, as a free radical scavenger, causes the attenuation of auditory brainstem response (ABR) threshold shifts resulting from noise exposure and noise plus CO exposure. Forty-two rabbits were divided into seven groups including control, noise + saline, noise + CO + saline, noise + α-tocopherol, noise + CO + α-tocopherol , CO + α-tocopherol and α-tocopherol alone. ABR was assessed before exposure, 1 h and 14 days post exposure. The administration of 50 mg/Kg of α-tocopherol prior, following and post exposure to noise or noise plus CO recovered permanent ABR threshold shift at 1 and 2 KHz almost to the baseline and provided significant attenuation in permanent ABR threshold shift at 4 and 8 KHz in subjects which were exposed to noise but it did not block the potentiating of threshold elevation by CO exposure (extra threshold loss by combined exposure) at 4 and 8 KHz. α-Tocopherol provides protective effect against the hearing loss resulting from noise exposure and simultaneous exposure to noise plus CO