선내 소음은 선원의 거주성과 건강을 위한 중요한 요소 중의 하나로, 선내 소음을 줄이기 위한 노력이 활발하게 진행되고 있 다. 소음 저감 방법에는 수동소음제어(PNC) 방법과 능동소음제어(ANC) 방법이 있다. 자동차, 항공기와 달리 선박에서는 ANC를 이용한 소음 저감 대책이 미미한 실정이다. 본 연구는 능동소음제어(ANC)와 같이 방음판과 고주파진동원을 이용하여 기관실에 발생한 소음을 줄이고자 하였다. 이를 위해 아크릴 상자를 이용하여 실험 모형을 만들었고, 4가지 조건별로 소음 저감 효과를 측정하였다. 실험 결과는 다음과 같다. 첫째, 방음판은 55 dB ~ 85 dB까지 모든 범위에서 소음 저감 효과가 있었다. 고주파진동원은 낮은 소음에서 효과가 없었으나, 70.8 dB(A)과 85 dB(A)와 같은 높은 소음에서는 효과가 있었다. 둘째, 방음판과 고주파진동원을 동시에 사용하는 경우에는 최대 -2.2 dB(A) 만큼의 소음 저감 효과가 있었다. 본 실험의 결과는 아크릴판으로 제작한 실험모형에서 얻은 결과로 철판으로 된 실제 선박과 다를 수 있 다. 추후 연구에서 실제 선박에서 사용하는 철판(재질과 두께, 구조를 고려)을 이용하여 실험하고자 한다. 이 연구가 선박에 승선하는 선 원들의 거주성 향상과 건강 증진에 도움이 되기를 기대한다.

소음공해는 인간과 해양환경에 악영향을 끼치며, 선박과 해양구조물에서 발생하는 유동소음을 예측을 통해 소음에 대한 안전 성을 평가하고 해양환경을 보존할 수 있다. 기존 수중구조 유동소음 해석기법은 전산유체역학과 FW-H음향상사식을 이용한 하이브리드법 기반이다. FW-H는 무한공간에서의 음향전파를 가정하여 소음해석을 수행하기 때문에 음파의 반사와 산란, 회절의 영향이 나타나는 근접 장 해석이 제한적이다. 반면 격자볼츠만기법 기반의 직접법 유동소음해석을 수행하면 근접장 음향효과를 소음해석에 반영할 수 있다. 직 접법 해석은 유동과 소음이 연성된 해석이 수행되고 구조경계에서의 반사와 회절, 유동에 의한 매질 불균일성에 따른 산란효과가 반영된 다. 그간 격자볼츠만기법이 수중조건에서 수치적으로 불안정하여 수중환경에 적용이 불가능했다. 하지만 수중환경에서 사용할 수 있는 DM-TS 격자볼츠만기법 충돌연산자가 개발되어 수중으로 확장이 가능해졌다. 본 연구에서는 파이프내 원형구멍에 대하여 격자볼츠만기 법 해석을 수행해 수중 유동소음해석이 가능함을 보였다. 격자볼츠만기법 해석을 통해 도출한 유동과 소음을 각각 실험과 비교하여 해석 의 신뢰도를 확보하였다. 파이프내 유동소음에 의한 주요 압력 피크가 해석에 반영되었으며 이를 통해 격자볼츠만기법을 이용한 근접장 유동소음해석이 가능함을 확인했다.

Aircraft noise is something humans don't want. In this study, based on the Rotax 914 engine used in Korea, the propeller blade angle was changed by 1 degree and the engine RPM was changed to review the three-wing “G Company” propeller and the three-wing GSC wooden propeller. Select the best propeller pitch angle by measuring the change in propeller noise and thrust and the change in engine RPM due to the change in noise and thrust. We would like to present a propeller pitch angle suitable for the location of the airfield and the operation of the aircraft. Based on this, we would like to help resolve noise complaints around the airfiled.

Noise is a sound that people don't want. In this study, noise is measured for SR20, a general aviation trainer used in Korea. In addition, noise measurement points are selected at Muan Airport, where most of the domestic trainers fly under the supervision of the Ministry of Land, Infrastructure and Transport, and the measured data are analyzed based on this. We also want to analyze the noise characteristics of SR20 aircraft through frequency analysis of the noise characteristics of SR20 aircraft are unique. We want to use this to understand what type of noise the trainer affects in future studies. this study will improve the reliability of the noise prediction scenario by comparing and analyzing the actual measured and predicted values when using the noise prediction program.

The noise of large and high-power machines was evaluated and the establishment of mitigation measures was studied. The noise level of large machinery and high-power machinery installed at domestic plant sites was investigated and compared with the noise disclosure regulations to see if they met the standards of the Occupational Safety and Health Act. This investigated the soundproofing design of large and high-power machines and the soundproofing design of complex noise of large machines installed in the plant, and prepared the design standards of the plant design company. In the future, we will compile a database of data to secure standards for research and plant design related to noise reduction, and propose noise improvement and management measures for large and high-power machines.

Metal material production process machinery is becoming larger due to the development of industry. Since there are many overseas manufacturers of large machines used in industrial fields, there are limitations in investigating the manufacturer's noise prediction method and measurement method. A noise map was prepared to obtain information necessary for noise reduction and to effectively manage noise companies. It was modeled with the drawings provided to prepare the noise map and the results of the actual measurement of the site. In order to improve the noise environment of workers, there was a noise reduction effect when a soundproof wall was installed between the noise source and the worker's workplace.

There is a considerable amount of research on metal material product worker’s hearing loss caused by noise that comes from manufacturing process. A further investigation that characterizes the sound that comes from manufacturing process of metal material products. however. To do this, a noise management plan is needed. It should include a generated sound process from the main sources of disturbance at manufacturing process areas. And a soundproof measurement will identify the amount of noise reduction needed for a hearing-safe working environment. Finally, researchers in this study measured tests on the noise and the vibration process, and the noise caused by operations allowed for an investigation on the suitability of certain environmental conditions. Noise-related programs can be used to predict the noise distribution of the noise level characteristic. This can help identify and reduce the presence of sound interference through sound proofing measures.

Most domestic pilots are trained at local airfields using propeller aircraft. Training aircraft are mainly trained in the airspace around the aerodrome, and mainly take-off and landing exercises that require a lot of practice among flight control skills. Aircraft noise is a sound that humans do not want. In this study, based on the Rotax 914 engine used in Korea, the propeller blade angle was changed by 1 degree for the 3-leaf “K company” propeller and the 3-leaf GSC wooden propeller, and the engine RPM was changed to examine the noise and thrust changes. The purpose of this study is to check whether noise and thrust loss are the least at the engine's maximum RPM, and to propose an aircraft operation plan in the noisy aerodrome area based on the values.

Environmental noise occurring on ships has various negative impacts on sailors’ health conditions such as hearing loss, sleep disturbance, psychological stress, etc., so regulations on them are required, but the ship noise regulations are usually applied to only large merchant ships. Although regulations on fishing boats with strong fishing and work intensity are determined to be necessary, there has been little relevant research. This study, therefore, attempted to measure the environmental noise of coastal composite fishing vessels less than two tones and provide the results of basic research on the noise regulations for fishing vessels. It measured them by setting the measurement zones as after side, midship and fore side, and based on the criterion of IMO MSC 337(91). The findings showed that the noise of them often exceeded 75dB(A), the criterion of the open deck noise in the zones in which the load of main engines was increased. In particular, the noise of the stern was as high as 92.2dB(A) during the full ahead. Hence, hearing loss may be caused by such a noise, so a variety of regulations on it are determined to be necessary.

Noise is a sound that humans do not want. In this study, noise is measured for C172, the most frequently used general aviation trainer in Korea and abroad. In addition, in this study, noise measurement points are selected for Muan Airport, where most of the domestic training aircraft fly under the supervision of the Ministry of Land, Infrastructure and Transport. Based on this, the measured data is scaled and analyzed. In addition, we intend to analyze what characteristics C172 aircraft have unique through frequency analysis of noise of C172. Through this, it is intended to understand what type of noise training aircraft affect in future studies.

Currently, many complaints have been filed by local residents on helicopter noise while the law on noise prevention and damage compensation at military airfields and military ranges has been in effect since November 27, 2020. The airfields operated by state agencies are inevitably used to defend the country, defend the country, and protect the lives of the people, but various efforts are needed to minimize noise complaints. In general, helicopters operating in a specific area exhibit different noise frequencies depending on the number or size of wings for each type, takeoff speed, and takeoff altitude. Therefore, by measuring and analyzing noise in the take-off stage of a number of helicopters operating in a specific area, this study aims to present more effective noise prevention measures by analyzing the compliance of each type of helicopter with variables such as take-off speed, take-off altitude, and rise rate. Therefore, the results of this study will be significant in terms of resolving complaints and reducing compensation expenditures of local residents around the airport.

Anomaly detection for each industrial machine is recognized as one of the essential techniques for machine condition monitoring and preventive maintenance. Anomaly detection of industrial machinery relies on various diagonal data from equipped sensors, such as temperature, pressure, electric current, vibration, and sound, to name a few. Among these data, sound data are easy to collect in the factory due to the relatively low installation cost of microphones to existing facilities. We develop a real time anomalous sound detection (ASD) system with the use of Autoencoder (AE) models in the industrial environments. The proposed processing pipeline makes use of the audio features extracted from the streaming audio signal captured by a single-channel microphone. The pipeline trains AE model by the collected normal sound. In real factory applications, the reconstruction error generated by the trained AE model with new input sound streaming is calculated to measure the degree of abnormality of the sound event. The sound is identified as anomalous if the reconstruction error exceeds the preset threshold. In our experiment on the CNC milling machining, the proposed system shows 0.9877 area under curve (AUC) score.

The main noise of a large machine can be divided into the noise generated during the work process and the noise of the equipment used in the work. The main noise in the noisy area is the air propagation sound caused by the operation of the rotating body. This is not fixed, but changes depending on the situation at the time of measurement. Workplaces exposed to noise can harm workers' health and cause related industrial disasters, resulting in many complaints and social problems, and eventually lead to a lot of damage in terms of productivity. Large machines that need noise reduction the most are motors, pumps, fans, blowers, and compressors. To reduce noise, mechanical structure or material changes are most effective. In this study, the noise reduction method and noise management method of large machines were investigated. To measure noise, the same method as ISO 3744 in Europe and JISA 8305 in Japan was used as KS A ISO 3744, KS A ISO 3746, which is a method of measuring the acoustic power level of machinery.

In this study, the noise reduction effect of the steam vent silencer was investigated by performing a transient flow analysis applying the Loss Model, a porous flow analysis model, and calculating the noise intensity from the pressure fluctuation according to the time change. As a result of flow analysis, it was confirmed that the noise intensity decreased as the number of diffusers and the number of splitters made of foamed aluminum increased. In the case of three-stage diffusers, the noise intensity decreased by up to 33.4 dB when six foamed aluminum with a thickness of 150mm were installed.

Due to the development of the industry, the machinery of plant facilities becomes large and operates at high speed and high power. Workers at plant facility sites are exposed to high noise and impact noise, and the number of people with noise-induced hearing loss is increasing every year. Therefore, in order to minimize such damage, many efforts have been made to reduce the noise of large machines in production facilities. Measures, education, and recommendation of wearing hearing protectors are needed to protect the hearing of workers in high noise industries. In addition, it is urgent to reduce noise sources by blocking noise propagation paths, such as installing noise boxes and silencers, and installing facilities and equipment that generate less noise. It is necessary to repair the noise reduction device of the large machine of the plant or to study the noise reduction device when designing the plant.