Preliminary Book of Abstracts From INTER-NOISE 2021 Proceedings Pleanaries, Keynotes, Technical Sessions, Latin American Symposium, and Workshops Papers are listed by Day, Channel, and Time Notes: 1. Links are not active in this document. 2. Minor changes to the schedule may be made and thus continue to check the Cadmium site (congress online platform) for updates. 3. Final document (Proceedings with active links) will be available only to the registered delegated in the Cadmium. 4. DOI indexing will become active following the conference. Session Number 04.00 Signal Processing, Measurements, Sound Reproduction, Diagnostics for Noise and Vibration Engineering, General, Part 1 - Channel 1 6:40 AM 01-Aug-2021 IN21_1136.pdf DOI: https://doi.org/10.3397/IN-2021-1136 Distortion measurements of sound pressure level generated by a pistonphone Thiago Antônio Bacelar Milhomem, Zemar Martins Defilippo Soares, Gustavo Palmeira Ripper, Peter Hanes, Adrian Solano Mena, Federico Ariel Serrano, Giancarlos Miguel Guevara Chuquillanqui, Juan Pablo Ayala Breña A supplementary interlaboratory comparison on pistonphone calibration was performed between 2018 and 2020 under the auspices of the Inter-American Metrology System. Seven national metrology institutes took part in this comparison. One pistonphone was circulated among the participants for measurement of the generated sound pressure level, frequency, total distortion + noise and total harmonic distortion. This paper presents the results of distortion measurements and analyzes them. From the stability check, notable variances with respect to reported measurement uncertainty were observed. From reported results, a large difference between the estimated uncertainties by the participants was noted. Convergence between results was found when measurements were performed using one-inch microphone while some divergence between results was found when measurements were performed using half-inch microphone. In addition, these results (using one-inch and half-inch microphones), even when obtained by the same institute, sometimes were different. Reasons for these findings are discussed and suggestions for future comparisons are presented. 7:00 AM 01-Aug-2021 IN21_2557.pdf DOI: https://doi.org/10.3397/IN-2021-2557 MEMS digital microphone and Arduino compatible microcontroller: an embedded system for noise monitoring Felipe Ramos de Mello, William D’Andrea Fonseca, Paulo Henrique Mareze Noise assessment and monitoring are essential parts of an acoustician's work since it helps to understand the environment and propose better solutions for noise control and urban noise management. Traditionally, equipment to carry out this task is standardized, and, eventually, expensive for the early career professional. This work develops a high-quality (and cost-effective) prototype for an embedded noise monitoring device based upon a digital I2S MEMS microphone and an Arduino compatible microcontroller, named Teensy. Its small size and low power consumption are also advantages designed for the project. The system captures and processes sound in real-time, computes A and C frequency-weighted equivalent sound levels, along with time-weighted instant levels with a logging interval of 125 ms. Part of the software handles the audio environment, while the biquadratic IIR filters present in the Cortex Microcontroller library are responsible for the frequency- and time-weightings — using floating-point for enhanced precision. The prototype results were compared against a Class 2 Sound Level Meter, rendering very similar results for the tested situations, proving a powerful and reliable tool. Improvements and further testing are also being INTER-NOISE 2021 Proceedings Page 1 conducted to refine its functioning and characterization. Ultimately, the prototype achieved promising performance, confirming as a solution for noise monitoring. 7:20 AM 01-Aug-2021 IN21_1580.pdf DOI: https://doi.org/10.3397/IN-2021-1580 Visualization of magnetic field corresponding to acoustic signal and estimation of magnetic source based on symmetry of magnetic field distribution Takuto Kurosawa, Takuto Kurosawa, Eri Ishizuka, Yasuhiro Oikawa, Masatoshi Asakawa, Yuya Suzuki A magnetic field corresponding to an acoustic signal is generated from an antenna, and by using a coil, can be again converted to an acoustic signal. It is possible to estimate where the invisible antenna is with the distribution of the received signal. The estimation is applied to a maintenance of a gas pipe on the situation that the distance from the entrance to a maintenance area is known, but piping route isn't. It is possible to identify maintenance areas of a gas pipe by inserting the antenna to it. The estimation has been done by listening to the received signal manually. However, it is difficult for people to identify accurate point because the difference in the volume for each places is subtle. To solve this problem, we visualized the distribution of the received signal, and estimated the magnetic field with only the acoustic signal. Then, we proposed a method to calculate where the invisible antenna is automatically by using symmetry of the distribution of the received signal. 7:40 AM 01-Aug-2021 IN21_3112.pdf DOI: https://doi.org/10.3397/IN-2021-3112 Measurement of loudspeaker mechanical impedance by changing the sound load at the throat of loudspeaker Shichun Huang, Liang Yu, Weikang Jiang A loudspeaker is a device that converts electrical energy into acoustic energy by coupling between electrical impedance, mechanical impedance, and radiation impedance. The loudspeaker electro-mechanical-acoustic coupling model provides the experimental feasibility to measure the characteristic parameters. In this paper, an economical and practical measurement method of loudspeaker mechanical impedance is proposed. First, the mathematical relationship between loudspeaker electrical impedance and mechanical impedance is obtained based on the loudspeaker electro-mechanical-acoustic coupling model. Second, two electrical impedances with different known radiation impedance are measured by using a developed measurement system. Finally, the real and imaginary parts of the mechanical impedance are obtained according to the mathematical relationship. This method neither assumes that the loudspeaker mechanical impedance is constant in a frequency band nor does it build FEM models based on structural parameters. A loudspeaker is measured by using a developed measurement system. The result shows that the mechanical impedance and the force factor are functions of frequency. Moreover, a radiation impedance measurement is performed to verify the feasibility and accuracy of the proposed method. 8:00 AM 01-Aug-2021 IN21_2757.pdf DOI: https://doi.org/10.3397/IN-2021-2757 Comparison of Estimation Methods of Room Impulse Responses in Local Region Using Small Number of Microphones Haruka Matsuhashi, Izumi Tsunokuni, Yusuke Ikeda Measurements of Room Impulse Responses (RIRs) at multiple points have been used in various acoustic techniques using the room acoustic characteristics. To obtain multi-point RIRs more efficiently, spatial interpolation of RIRs using plane wave decomposition method (PWDM) and equivalent source method (ESM) has been proposed. Recently, the estimation of RIRs from a small number of microphones using spatial and temporal sparsity has been studied. In this study, by using the measured RIRs, we compare the estimation accuracies of RIRs interpolation methods with a small number of fixed microphones. In particular, we consider the early and late reflections separately. The direct sound and early reflection components are represented using sparse ESM, and the late reflection component is represented using ESM or PWDM. And then, we solve the two types of optimization problems: individual optimization problems for early and late reflections decomposed by the arrival time and a single optimization problem for direct sound and all reflections. In the evaluation experiment, we measured the multiple RIRs by moving the linear microphone array and compare the measured and estimated RIRs. Session: Plenary Lecture Channel 1 9:45 AM 01-Aug-2021 IN21_1302.pdf DOI: https://doi.org/10.3397/IN-2021-1302 Soundscape: Progress in the past 50 years and challenges in the next 50 years Jian Kang Soundscape is defined by the ISO as the ‘acoustic environment as perceived or experienced and/or understood by a person or people, in context’. Different from conventional noise control engineering, soundscape promotes a holistic approach, regarding sounds as ‘resources’ rather than just ‘wastes’. This paper first briefly reviews the soundscape progress in the past 50 years, showing that there has been a recognised focus shift from noise control to soundscape creation, and also a step change from soundscape concept to practice. Then the current developments and needs in soundscape are dis-cussed in terms of soundscape understating and exchanging, collecting and documenting, harmonis-ing and standardising, creating and designing, and outreaching, showing that while considerable works have been carried out, much work is still needed, in terms of basic research, and more im-portantly, research towards practice. Finally, some major challenges in the next 50 years are ex-plored, considering the new industrial revolution, climate change and changing living styles. INTER-NOISE 2021 Proceedings Page 2 Session: Latin American Symposium: Environmental Noise Management Channel 1 11:30 AM 01-Aug-2021 Oral Only Environmental