Characteristics of Evacuation Guidance Sounds for the Visually-Impaired during Fire Alarms

Recently, various intelligent evacuation guidance systems that can be applied in buildings were studied. Technology development for the evacuation of vulnerable people such as the visually-impaired is necessary. Voice guidance is a method used to lead the visually-impaired toward the evacuation route. However, it is necessary to review whether it is possible to hear and understand the voice guidance during the sounding of fire alarms. In this study, simulations were conducted to predict the sound power level of the voice guidance device that can secure an acceptable sound transmission index of the guide sound and the appropriate distance from the voice guidance device, when a fire alarm sound is generated in a hallway space. The study found that an acceptable sound transmission index was achieved when the sound power level was 100 dB and the appropriate type of sound device was found to be a necklace-type headset or a regular headphone.

Trailing Edge Thickness Effect on Tonal Noise Emission Characteristics from Wind Turbine Blades

Broadband noise generation from wind turbine blades is one of the fundamental aspects of flow-induced noise. Besides the turbulent boundary layer flow over the blades, factors such as the angle of attack, the turbulence intensity, the trailing edge thickness of the blade and their shapes strongly influence the overall sound power levels at high frequencies, i.e. f > 8 kHz. In large operating wind farms, a trade-off between noise generation and power production is considered by power utility firms to maximize the return on investment (ROI) and minimize the fatigue damage on wind turbine components. The present work deals with the analysis of the thickness effect on trailing edge bluntness noise level at hub height average wind speeds of 7 m/s, 10 m/s. A semi-empirical BPM model was used to predict the sound pressure levels from the 37 m blade length of a 2MW wind turbine. The receiver configuration was fixed at a distance of 120 m from the source height of 80 m. The results demonstrated that as the trailing edge height increased from 0.1 % to 0.5 % of the local chord, the sound power level increased by ~ 17 dB for frequencies > 200 Hz, but decreased by 16 dB when the thickness is 0.1 % local chord. The computed results of the sound power level using the BPM model have been validated using experimental data and showed a good agreement for the tonal frequencies, f ~ 10 kHz, where the trailing edge bluntness noise becomes dominant.

Reducing the noise level of power transformers

The results of studies of the noise of power transformers at the enterprises of the machine-building complex are presented in this paper. The causes of the noise of power transformers are identified, the analysis is made, and the main design indicators affected the increase in the sound power level of high-voltage converters are determined. Based on the analysis of design indicators, organizational and technical measures are proposed for improving reliability and accident-free operation of power transformers, as well as reduction of the noise level of power transformers.

Potential noise annoyance from ambient air quality measurement using high volume air sampler (HVAS)

One of the benchmarks in air pollution is the quality of ambient air consisting of gas and particulate matter. Measurement of particulates in ambient air can be done using a High-Volume Air Sampler (HVAS). However, in the measurement process it sometimes causes noise annoyance to the community where the measuring instrument is operated, considering that the operating time of the instrument is 24 consecutive hours. This research identifies the value of the sound power level emitted from the several types of HVAS to the surrounding environment. There are two types of HVAS measured in this study consisting of one unit of HVAS with analogue flow control made by Indonesian manufacturer and two units of HVAS with digital flow control made by Japan and United States of America manufacturers. Sound power level is determined using ISO 9614 method with a sound intensity analyzer as the main instrument. The sound power level data for each HVAS were than compared and frequency spectrum distributions are evaluated. Based on the research results, it was found that some sample units emitted sound power levels of more than 90 dBA with dominant noise being at high frequencies starting from 4000 Hz. The results of the research can be used as an early information in the development of the HVAS regarding noise mitigation, because there is different approach for controlling noise specifics in low, mid and high frequencies noise source.

Pendampingan Pembelajaran Keterampilan Secara Daring di Pondok Pesantren Tarbiyatul Iman Malang

Pengabdian pada masyarakat ini bermitra dengan Pondok Pesantren Tarbiyatul Iman (PPTI), Malang. Pondok mengalami kesulitan penyelenggaraan pembelajaran praktek memasak, pada kondisi pandemi. Pengajar tidak diperkenankan bertemu tatap muka langsung di kelas. Sedangkan pelajaran praktek membutuhkan pengamatan, pembimbingan secara langsung pada saat pelaksanaan. Tujuan pengabdian pada masyarakat ini adalah mendapatkan solusi pembelajaran keterampilan memasak yang terkendala akibat pandemi covid-19. Metodenya adalah pengajar (pengajar) mengajar secara daring, sedang santri berada di kelas praktek bersama. Video tutorial memasak, yang dibuat pengajar di share lebih dulu kepada santri 3 hari sebelum pelajaran. Pengajar mengajar secara online, di ruang guru, menggunakan laptop, dan peralatan bantu extended monitor, microphone smartphone, sound power. Di ruang kelas praktek disediakan laptop untuk komunikasi dengan pengajar, dan juga dilengkapi IP camera yang terhubung dengan laptop/ smartphone pengajar. IP camera dapat dikendalikan menghadapnya sehingga seakan akan pengajar ada di kelas. Masakan yang dicobakan salah satunya adalah makanan yang disukai pada umumnya remaja, dalam hal ini dipilih mie Jepang. Bumbu dan topping semaksimalnya disesuaikan dengan resep aslinya, yang didapatkan di pasar lokal. Masakan dipresentasikan/ disajikan dalam wadah ala restoran. Evaluasi hasil memasak melibatkan pengajar/ ustad lain. Santri dapat mengikuti kegiatan ini dengan baik, mengikuti dengan gembira, dipandu dengan baik, aktifitas santri terpantau dengan baik, dan hasil masak yang memuaskan. Pengajar dapat melaksanakan pembelajaran kelas secara daring-luring, lebih terampil menguasai berbagai peralatan, lebih mudah dalam memantau kelas, dan mudah dalam mengevaluasi. Kegiatan ini berhasil dilaksanakan dengan baik dan dapat dijadikan raw model pembelajaran praktek secara daring-luring. Aman mengikuti protokol pencegahan covid 19.

Temperature Effects in an Acousto-Optic Modulator of Terahertz Radiation Based on Liquefied SF6 Gas

The acousto-optic (AO) diffraction of terahertz (THz) radiation in liquefied sulfur hexafluoride (SF6) was investigated in various temperature regimes. It was found that with the increase in the temperature from +10 to +23∘C, the efficiency of the AO diffraction became one order higher at the same amplitude of the driving electrical signal. At the same time, the efficiency of the AO diffraction per 1 W of the sound power as well as the angular bandwidth of the efficient AO interaction were temperature independent within the measurement error. Increase of the resonant sound frequency with decreasing temperature and strong narrowing of the sound frequency bandwidth of the efficient AO interaction were detected.