Octave Frequency Research Articles

Scalable Antenna Arrays Featuring Stable Radiation Pattern in Multioctave Bandwidth

This article proposes a novel concept of antenna arrays operating in the multiple-octave frequency range. The antenna arrays ensure steady half-power beamwidth (HPBW) in <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$2^{N}$ </tex-math></inline-formula> :1 bandwidth (BW) due to the proper placement of radiating elements and appropriate signal switching between them. The proposed arrays consist of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$N+1$ </tex-math></inline-formula> centered subarrays that are electrically similar at successive frequencies. The antenna arrays are fed by networks composed of power dividers and directional filters responsible for gradual RF power shift from the elements operating at the lowest frequency to the elements operating at the highest frequency. The directional filters utilize the same properly scaled switching function for every frequency octave in the operational frequency range. The presented concept has been verified by the design of antenna arrays operating over 1.2–4.8 (4:1 BW) and 1.2–9.6 GHz (8:1 BW) frequency ranges.

Engineered octave frequency comb in integrated chalcogenide dual-ring microresonators

Octave-spanning Kerr combs bridging the spectral windows of the near-infrared region (NIR) and the mid-infrared (MIR) region are expected in a number of applications, including high-capacity coherent optical communications, and gas molecular absorption footprints. Here, we propose novel concentric dual-ring microresonators (DRMs) for advanced dispersion engineering to tailor the comb spectral profile. The dispersion can be flexibly engineered not only by the cross-section of the DRMs, but also by the gap between concentric dual-ring microresonators, which provides a new path to geometrically control the spectral profile of the soliton Kerr combs. An octave-spanning Kerr soliton microcomb with multi-dispersive waves has been achieved numerically covering from the telecommunication band (1224 nm) to the mid-infrared band region (2913 nm) with a −40 dB bandwidth of 1265 nm. Our results are promising to fully understand the nonlinear dynamics in hybrid modes in DRMs, which helps control broadband comb formation.

Possibility to apply unified methodology in vibration analysis for long lasting and impulse sources, in terms of influence on people in buildings

The present work addresses the problem of unified methodology use for vibration analysis caused by various anthropogenic sources. The experimental part of the paper contains analysis and results comparison of the vibration, induced by freight train passages and hammer percussion. Ground vibrations are important for the civil engineering objects condition since the vibration induced by train is transmitted through the ground to the foundation and structure. Ground vibration can also be a source of disturbance for the residents. However, various factors cause vibration that varies in both intensity and frequency measures. The analysis of vibration timelines, running RMS and Fourier spectra are applied. The major part of the dissertation is the analysis of RMS accelerations and velocities in one-third octave frequency bands in 1 to 80 Hz spectrum, and comparison to the background vibration noise, recorded in the same localisation. The different values of time-window observation are applied to analyse the results. The results of long lasting cargo-induced vibrations are less dependent on time-window duration than the results of impulse-induced vibrations. The acceleration and velocity analysis results are compared to the literature data concerning the ground vibration caused by railway transport and mining activity. The paper indicates the possibility to apply unified methodology for vibration analysis caused by both long-lasting sources, as trains and short-lasting ones, as industrial blasts or mine tremors. The results indicate an optimal time window for vibration measurement that would enable to automate vibration monitoring.

Localization of Noise Sources in Jets Flowing from Lobed Nozzles

The noise of jets formed using conical and lobed nozzles has been measured. The possibility of jet noise reduction by using a lobed nozzle shape has been demonstrated. The localization of noise sources in jets formed using various nozzles has been carried out. A planar 9-beam 54-channel Bruel &amp; Kjaer micro-phone array and Delay-and-Sum Beamforming technique were used. As a result, the position of noise sources in a turbulent jet in one-third octave frequency bands was obtained. The deviation effect of the position of noise sources when using lobed nozzles relative to the standard jet formed by a conical nozzle is demonstrated.

Fabrication of green composites by waste coconut shells as partial replacement of coarse aggregates in concrete and determination of its acoustic behaviour

Nowadays, natural materials have been frequently used for sound absorption in constructions and buildings. This paper has characterised the acoustic behaviour of coconut shell reinforced concrete composite with partial substitution of coarse aggregates in terms of sound absorption at octave frequency signals (32 Hz-16 kHz). Composites have been prepared in different weight percentages (5%, 10%, 15%, and 20%) of partial substitution of coarse aggregates. The acoustic test has been conducted in a 3.5 mm thick glass box without and with samples by point method of sound power measurement. The results have demonstrated that the value of the sound pressure level has decreased at different points with the increased percentage of coconut shells in composite, hence increasing the sound absorption coefficient of the concrete. The results have also been compared with conventional concrete composite. Additionally, the results have indicated that these concrete blocks can significantly absorb sound in the mid-frequency range. Generally, a sound absorption coefficient greater than 0.2 for any material qualifies it as a sound-absorbing material, and a sound absorption coefficient greater than 0.6 for any material is known as the best sound absorber. Therefore, developing such green composites can be an eco-friendly approach to the acoustic community.

Study of Noise Reduction and Sound Absorption Performance of Drainage Asphalt Pavement Based on Indoor Tire Accelerated Falling Method

In order to study the noise reduction and sound absorption performance of drainage asphalt pavement and porous asphalt concrete (PAC) and the difference of noise reduction and sound absorption effects of conventional AC pavement, single-layer and double-layer PAC pavements are compared and analyzed by improving the indoor noise test of tire accelerated falling method, and then the sound absorption coefficient of single-layer and double-layer PAC pavement is further tested using the standing wave tube method. Based on the standing wave interference principle of sound, the sound absorption characteristics of drainage asphalt pavement are described, the influence of void ratio on the sound absorption coefficient of PAC pavement is analyzed, and the data model between the void parameters and sound absorption coefficient is established. The results show that: (1) using the improved indoor tire accelerated falling method and using the sound level meter to measure the A-weighted sound pressure level and 1/3 octave frequency spectrum of noise under three distance conditions, the noise value of drainage asphalt pavement is 2 to 5 dB(A) lower than that of traditional AC pavement, and the noise reduction ability decreases with the increase of distance from the sound source and increases with the increase of void ratio. The sound absorption coefficient curve of drainage asphalt pavement is measured using the standing wave tube double transfer function method. The average sound absorption coefficient of PAC specimens decreases with the decrease of the void fraction. (2) The sound absorption coefficient curve of single-layer PAC pavement presents a “single peak type”. The sound absorption peak frequencies of a single layer 4 cm-thick PAC pavement and 10 cm-thick PAC pavement are around 1100 Hz and 800 Hz respectively. The corresponding frequencies of the sound absorption peaks of the two specimens are within the common frequency range of traffic noise, which is helpful to alleviate traffic noise. (3) Through CT scanning and three-dimensional reconstruction software, the void parameters of the PAC specimen are obtained, and the sound absorption coefficient prediction model is established. The sound absorption coefficient calculated by the model has a high correlation with the measured value of standing wave tube method, which verifies the accuracy of the sound absorption coefficient model in predicting the sound absorption characteristics of drainage asphalt pavement.

Rethinking the Audiogram for Hearing Aid Selection

Rethinking the Audiogram for Hearing Aid Selection

Urban workers' cardiovascular health due to exposure to traffic-originated PM2.5 and noise pollution in different microenvironments

The cardiovascular health of the people in urbanised cities is linked to traffic air, and noise pollution. This study investigated the cardiovascular health of people working in two microenvironments such as street (vendors) and workplace (office workers) whose blood pressure (BP) and heart rate (HR) might be affected due to regular exposure to PM2.5 and traffic noise. The PM2.5 and noise levels measurements, face-to-face questionnaire survey and health check-ups were carried out on working days from 10 A.M. to 8 P.M. in Jan-Dec 2019. The data was analysed by various statistical approaches in which the link between the traffic-borne PM2.5 and noise level at 1/3rd octave frequencies has been established with the participants' BP and HR considering the demographic, socio-contextual, habitual and annoyance perception factors. The median measure of PM2.5 and noise levels violated the WHO and NAAQS limits, i.e. 106.67 μg/m3 at street level and 33.33 μg/m3 at office indoor; and 71.35 dB (A) at the street and 65.78 dB (A) at office indoor. The results further showed that the workers working in traffic corridors had abnormally high BP and HR. The systolic BP, diastolic BP and HR values were higher than normal in male workers than female workers. The influence of low noise spectrum (50–630 Hz) was mostly observed. Therefore, the combined effect of PM2.5 > 50 μg/m3 and noise spectrum (63 and 100 Hz) > 30 dB (A) significantly affect office workers' health in traffic corridors. The hearing aids, breathing troubles in the traffic corridor and annoyance perception also influenced the BP and HR of the respondents. The results are indicative and might be helpful in urban environmental planning to improve the well-being of urban traffic corridor users.

Evaluation of middle ear and hearing status of ankylosing spondylitis patients with wideband tympanometry and pure tone audiometry tests.

The aim of this study was to evaluate the middle and inner ear function and hearing status of Ankylosing spondylitis (AS) patients. One hundred twenty-four ears of 62 patients with AS and 90 ears (control group) of 45 healthy subjects were included in the study. The hearing levels of the participants were assessed with pure tone and high-frequency audiometry at the octave frequency between 250 and 16,000Hz. The absorbance rates and resonance frequencies of middle ear were measured with the wideband tympanometry (WBT) test. AS group was divided into subgroups based on the disease activity, duration of follow-up, medications used for AS, and the subgroups were compared according to hearing status and absorbance and resonance frequencies of middle ears. A statistically significant difference was found between the AS and control groups in terms of air and bone conduction thresholds at frequencies of 250, 500, 1000, 2000, and 4000Hz and the mean PTA1, PTA2, and PTA3 values (p < 0.05). In contrast, no statistically significant difference was observed between two groups in terms of high-frequency thresholds (8000-16,000Hz). Although the middle ear resonance frequency obtained from the WBT test was higher in the AS group compared to the control group, no significant difference was observed (p > 0.05). The severity of disease adversely affected the hearing threshold at 250, and 500Hz for air conduction, at 500Hz for bone conduction threshold, and at PTA1 (p < 0.05). The duration and severity of disease did not affect absorbance values of WBT (p > 0.05). To our knowledge, this is the first study to demonstrate the effects of AS patients on the middle ear function with WBT and to report middle ear absorbance values and resonance frequency changes in AS patients. The higher resonance frequency values found by WBT in AS patients may be due to the stiffness that develops as a result of middle ear involvement. According to pure tone and high-frequency audiometry findings, it has been seen that AS leads to SNHL especially at low frequencies.

A Compact Wideband Multi-Beam Antenna for VHF/UHF Directional Networking Applications

We propose a wideband multibeam circular array antenna for directional networking applications at VHF/UHF frequencies. We introduce a directional antenna element by combining the radiation patterns of a monopole and a loop element. Combining the figure-eight-shaped and omnidirectional radiation patterns of the loop and the monopole antenna results in a directional antenna element. We demonstrate that a significantly larger bandwidth can be achieved by moderately relaxing the size constraints placed on the antenna element. A circular array consisting of eight of these radiating elements was developed. This array has a low profile, fitting in a 4 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times $ </tex-math></inline-formula> 4 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times $ </tex-math></inline-formula> 1 ft3 volume. The antenna shows a well-matched frequency response with S11 below −10 dB over an octave frequency bandwidth of 225–450 MHz. The good impedance matching of the array is maintained if the array elements are individually excited (e.g., to provide eight beams) or if multiple adjacent elements are excited together to provide fewer, more directional beams. We validated our simulation results by fabricating and experimentally characterizing a 3:1 scaled model of the proposed antenna. The proposed array can achieve gain values of 6–8 dBi within its operational bandwidth if each radiating element is excited individually. This gain increases to 10–12 dBi by exciting three adjacent elements.

Evolution of the dawn chorus throughout the breeding season at an inland migratory bird refuge

The dawn chorus is a defining acoustic event for many environments with vocal bird populations. To study short and long-term changes in spectral characteristics of the dawn chorus at an inland migratory bird refuge, Larson Davis 831C sound level meters (SLM) were deployed at Utah’s Bear River Migratory Bird Refuge from March to August in 2021 and 2022, overlapping with the breeding seasons of many resident and migratory species of birds. The SLMs collected one-second temporal resolution data in one third octave (OTO) frequency resolution both years, as well as audio recordings during 2022. The relative contributions of the bird-relevant OTO bands (∼500 Hz–12.5 kHz) to the total energy are analyzed for each chorus. One result shows that the chorus’s spectral composition varies markedly for different locations within the refuge throughout the breeding season. The results show the value of the relatively low-resolution data in studying overall chorus characteristics. Additionally, the audio recordings have been analyzed using BirdNET species identification software to correlate changes in chorus characteristics with changes in species and behavior over the breeding season.

International Monitoring System infrasound data products for atmospheric studies and civilian applications

Abstract. The International Monitoring System (IMS) was established in the late 1990s for verification of the Comprehensive Nuclear-Test-Ban Treaty (CTBT). Upon completion, 60 infrasound stations distributed over the globe will monitor the Earth's atmosphere for low-frequency pressure waves. In this study, we present advanced infrasound data products of the 53 currently certified IMS infrasound stations for atmospheric studies and civilian applications. For this purpose, 18 years of raw IMS infrasound waveform data (2003–2020) were reprocessed using the Progressive Multi-Channel Correlation (PMCC) method. A one-third octave frequency band configuration between 0.01 and 4 Hz was chosen to run this array-processing algorithm which detects coherent infrasound waves within the background noise. From the comprehensive detection lists, four products were derived for each of the certified 53 IMS infrasound stations. The four products cover different frequency ranges and are provided at the following different temporal resolutions: a very low-frequency set (0.02–0.07 Hz, 30 min; https://doi.org/10.25928/bgrseis_bblf-ifsd, Hupe et al., 2021a), two so-called microbarom frequency sets – covering both the lower (0.15–0.35 Hz, 15 min; https://doi.org/10.25928/bgrseis_mblf-ifsd, Hupe et al., 2021b) and a higher (0.45–0.65 Hz, 15 min; https://doi.org/10.25928/bgrseis_mbhf-ifsd, Hupe et al., 2021c) part – named after the dominant ambient noise of interacting ocean waves that are quasi-continuously detected at IMS stations, and observations with center frequencies of 1 to 3 Hz (5 min), called the high-frequency product (https://doi.org/10.25928/bgrseis_bbhf-ifsd, Hupe et al., 2021d). Within these frequency ranges and time windows, the dominant repetitive signal directions are summarized. Along with several detection parameters, calculated quantities for assessing the relative quality of the products are provided. The validity of the data products is demonstrated through example case studies of recent events that produced infrasound detected at IMS infrasound stations and through a global assessment and summary of the products. The four infrasound data products cover globally repeating infrasound sources such as ocean ambient noise or persistently active volcanoes, which have previously been suggested as sources for probing the winds in the middle atmosphere. Therefore, our infrasound data products open up the IMS observations also to user groups who do not have unconstrained access to IMS data or who are unfamiliar with infrasound data processing using the PMCC method. These types of data products could potentially serve as a basis for volcanic eruption early warning systems in the future.

EXPERIMENTAL EVALUATION OF THE ANTIVIBRATOR TECHNICAL CONDITION

One of the key problems that have developed today in the fleet during the operation of ships is the termination of supplying products from leading foreign manufacturers of dampers and antivibrators of torsional vibrations, which ensure the safe operation of critical elements of the engine complex. Also, the next confirmation of relevance is the fact that there are no maintenance service centers on the territory of the Russian Federation, nor specialists who carry out the defection and repair of such devices. The results of experimental studies to assess changes in the technical condition of the antivibrator, which is the driven part of the clutch disc of a well-known foreign manufacturer for a KAMAZ truck, at the laboratory stand of the Marine Technology Service testing center of the Astrakhan State Technical University, are presented in the paper. The purpose of the tests is to evaluate the changes in vibration and torsional vibrations occurring in the elements of the laboratory stand at different states of the damping springs of the antivibrator. It should be noted that this device is used on YAMZ-236 engines, which is convertible on the ship. The change in the technical condition of the antivibrator is ensured by a complete limitation of the stroke (jamming) of the damping springs. Mechanical jamming is performed sequentially for each spring package and by measuring tangential stresses in the shaft of the laboratory stand and vibration acceleration on the bearing assembly rack. To conduct the experiments, the measuring base of the test center, including a torsional vibration monitoring system, a 1st class vibrometer, an Ecophysics-110 spectrum analyzer, etc., is used. It has been experimentally established that when the free travel of the damping springs of the anti-vibrator is completely limited, tangential stresses in the shaft and vibrations on the bearing assembly of the laboratory stand increase. It is also determined that the average tangential stresses in the shaft are more effective in terms of the criterion for diagnosing the antivibrator technical condition than the maximum stresses. The most informative for antivibration diagnostics are the octave frequencies of 4, 63 and 125 Hz, at which there is a significant change in vibration acceleration along all three axes X, Y, Z, depending on the number of jammed springs. The accumulation of theoretical and practical research in this area, in the future, may lead to the development of a methodology for the non-selective assessment of the technical condition of ship mechanical dampers and antivibrators of torsional vibrations.

Two-colour high-purity Einstein-Podolsky-Rosen photonic state

We report a high-purity Einstein-Podolsky-Rosen (EPR) state between light modes with the wavelengths separated by more than 200 nm. We demonstrate highly efficient EPR-steering between the modes with the product of conditional variances {{{{{{{{mathcal{E}}}}}}}}}^{2}=0.11pm 0.01ll 1. The modes display − 7.7 ± 0.5 dB of two-mode squeezing and an overall state purity of 0.63 ± 0.16. EPR-steering is observed over five octaves of sideband frequencies from RF down to audio-band. The demonstrated combination of high state purity, strong quantum correlations, and extended frequency range enables new matter-light quantum protocols.

Dynamic and sound radiation characteristics of a non-uniformly heated isotropic plate

The influence of non-uniform heating on the anisotropic plate’s dynamic and acoustic response characteristics is investigated numerically. The effect of non-uniform heating on the plate is accounted in the form of pre-stress developed on the plate due to non-uniform heating of the plate. The influence of structural boundary conditions, nature of temperature variation, and level of temperature on vibration and acoustic response characteristics are investigated in detail. Thermal buckling strength and fundamental buckling mode are highly sensitive to the nature of temperature variation across the plate. Free vibration mode shapes of the plates with high aspect ratio and free edges are changing their pattern with an increase in temperature. The resonant amplitude of sound power radiated associated with a particular mode is dominated by vibration nodes and anti-nodes shifting relative to the excitation location. Further, an increase in sound power level with an increase in temperature is observed clearly in the lower octave frequency bands.

Relative Importance for Lincoln’s Sparrow (Melospiza lincolnii) Occupancy of Vegetation Type versus Noise Caused by Industrial Development

Anthropogenic noise can create an acoustic environment detrimental for animals that communicate using acoustic signals. Currently, most studies of noise and wildlife come from traffic noise in cities. Less is known about the effects of noise created by industry in natural areas. Songbirds far from cities, but influenced by industry, could be affected by noise, but also are likely to be impacted by changes in vegetation conditions related to industrial development. We described the importance of industrial noise (from facilities and transportation) on occupancy of Lincoln’s Sparrow (Melospiza lincolnii) relative to habitat change caused by vegetation alteration and edge effects. Lincoln’s Sparrows naturally breed in varying seral stages and types of boreal forest. To test the influence of industrial noise, we selected three areas in Northern Alberta, Canada with high, medium, and low levels of industrial development and varying road density. At each area, we deployed a systematic arrangement of autonomous recording units (280 units in total, separated by 600 m) for 3 consecutive days. To measure noise, we developed a method that used the relative noise values extracted from the recordings of 8 frequency-octave bands. We obtained three noise measurements: noise with high energy in the low part of the spectrum (mean 0.5–1 kHz), masking level noise (mean 2–8 kHz), and noise in all frequency octave bands (mean 0.5–16 kHz). Proportion of chronic noise sources explained the highest variation of noise in the environment, and less by traffic noise. We found Lincoln’s Sparrow had a higher occupancy in areas with higher proportion of industrial disturbances, shrubs and grass, and decreased in noisy areas. Masking level noise had a negative effect on Lincoln’s Sparrow occupancy in areas with industrial disturbances, relative to areas with similar changes in vegetation structure, but no noise. Masking noise could indicate limitation in communication as noise increases. Our study amplifies the findings of others that future research should consider not only anthropogenic changes to vegetation in human-altered landscapes, but also human-caused changes to acoustic environments.

Idiopathic Sudden Sensorineural Hearing Loss in Different Ages: Prognosis of Patients With Initial Total Hearing Loss.

ObjectiveThis study aimed to analyze the hearing improvement and prognosis factors of idiopathic sudden sensorineural hearing loss (ISSNHL) in different ages with initial total hearing loss.MethodsWe reviewed the medical records of 5,711 hospitalized patients with ISSNHL from 2016 to 2021 in our center. All of the patients had been treated with uniform combination drug therapy. After excluding the patients with initial partial hearing loss and those diagnosed with clear etiology, 188 patients were enrolled in this study and divided into six age groups (18–30, 31–40, 41–50, 51–60, 61–70, ≥ 71 years). In all groups, decreases in pure-tone average (PTA) 1 month posttreatment, effective rate, and clinical characteristics (vertigo, tinnitus, hospital stay, comorbidity, and inner ear magnetic resonance imaging) were analyzed.ResultsAmong the 188 enrolled patients, 86% had vertigo. Complete recovery was seen in 0.5% of patients, and marked recovery was seen in 43% of patients. The mean 1 month posttreatment PTAs were as follows: 18–30 years: 80 ± 7.5 dB; 31–40 years: 100 ± 9.0 dB; 41–50 years: 99 ± 8.3 dB; 51–60 years: 101 ± 8.6 dB; 61–70 years: 96 ± 9.6 dB; and ≥ 71 years: 88 ± 13.0 dB. Compared with the other groups, the 18–30- years group showed better recovery of hearing threshold in five frequencies (0.25, 0.5, 1, 2, and 4 kHz, respectively, at octave or semioctave frequencies under air conduction), and the recovery of hearing threshold at 0.25 and 0.5 Hz was better than the recovery at 1, 2, and 4 kHz. According to the results of the chi-square test statistical analysis, vertigo and comorbidities were associated with a poor prognosis of ISSNHL.ConclusionIn summary, the treatment outcomes of patients with ISSNHL with initial total hearing loss were poor. There was a significant age-related difference with respect to marked recovery 1 month posttreatment, and the 18–30- years group showed better recovery than the other age groups.

Mid-infrared silicon-on-insulator waveguides with single-mode propagation over an octave of frequency.

Increasing the working optical bandwidth of a photonic circuit is important for many applications, in particular chemical sensing at mid-infrared wavelengths. This useful bandwidth is not only limited by the transparency range of waveguide materials, but also the range over which a waveguide is single or multimoded for predictable circuit behaviour. In this work, we show the first experimental demonstration of "endlessly single-mode" waveguiding in silicon photonics. Silicon-on-insulator waveguides were designed, fabricated and characterised at 1.95 µm and 3.80 µm. The waveguides were shown to support low-loss propagation (1.46 ± 0.13 dB/cm loss at 1.95 µm and 1.55 ± 0.35 dB/cm at 3.80 µm) and single-mode propagation was confirmed at 1.95 µm, meaning that only the fundamental mode was present over the wavelength range 1.95 - 3.80 µm. We also present the prospects for the use of these waveguides in sensing applications.

The efficiency of hearing protective devices against occupational low frequency noise in comparison to the new subjective suggested method

Noise is one of the most important occupational and environmental health hazards. Exposure to loud noise can cause irrevocable hearing damage and loss of hearing. The aim of this study was to determine the efficiency of two samples of earmuff and earplug in low frequency noise reduction in comparison to subjective method. All the procedures of the work were done using the simulated human ear canal and the required microphone in the eardrum. At the octave frequencies, that is 31.5 and 63.5, 125, 250, 500, 1000, 2000, 4000, and 8000 Hz, and intensities of 85-90 dB, one stage was done by using the individual's subjective response relative to the received sound before and after using the ear protector. The sound levels before and after the protection were significantly different in both the model and humans (P < 0.05). However, at 315 Hz frequency, the rate of attenuation is increased by 4 dB after placing the earplug and 14 dB after placing the earmuff, showing a reduction of 18 dB. This study verifies the increasing protection by simultaneous application of earplugs and earmuffs. Because of the laboratory evaluation of ear protectors, it is possible not to justify the proficiency of ear protectors in a subjective method.

Frequency of hearing loss among medical students using electroacoustic device.

Objective:To determine frequency of hearing loss among medical students using electroacoustic devices like hands free, headphone etc. through Pure Tone Audiometry.Methods:This cross-sectional study was conducted among students at JSMU from December 2019 till February 2020. Ethical approval was obtained against Ref: JSMU/IRB/2019/-215. Calculated sample size was 194. Non-probability convenience sampling technique was employed. Students were invited to ENT OPD JPMC, Karachi. After informed consent, sociodemographic and electroacoustic device usage history was recorded. PTA was performed at octave frequencies for air (0.25-8kHz) and bone conduction (0.5kHz-4kHz). WHO grading of hearing impairment was used. Statistical analyses carried through IBM SPSS. Chi square test, Fischer exact test and independent t test were applied at 95% CI and p value <0.05 as statistical significance.Results:Out of 246 students, 221 fulfilled inclusion criteria. Male to female ratio was 1:3. Mean age was 21 years (S.D: ±0.927). 96.4% were regularly using electroacoustic devices. 47.9% reported their use over five years. Insert type earbuds (73.8%) were the most preferred. Smartphone being the most common source (90%). Upon PTA, one third of medical students demonstrated sensorineural hearing loss at 0.25kHz and 0.5kHz. 9.5% reported associated tinnitus. Daily listening duration exceeded one hour among 78.8% while 26.4% practiced high volume setting. Males’ average listening duration exceeded that of females (p=0.013). However, their mean audiometric thresholds did not vary significantly.Conclusions:Mild sensorineural hearing loss was detected among one third of participants using personal listening devices. Precautions should be practiced while using these devices.