In MalaysiaSouvenir shot taken while Hosoi was stationed overseas on sales activities.Malaysia (photographed here) and Thailand became the main stage in the first step to expand sales of RACS overseas.moment. at proved short-lived. It really wasn’t an easy task, because to calibrate microphones and sound level meters, acoustic couplers emit sound over a wide range of frequencies. If per-formance needed to be managed for just one speci c frequency—say, 250 Hz or 1 kHz—then we already had estab-lished methods for enhancing the repe-tition reproducibility of measurements. But in the case of RACS, the acoustic coupler is used to manage the perfor-mance of sound level meters and micro-phones over the incredibly broad fre-quency range of 1 Hz to 20 kHz. at increases the di culty several-fold. I don’t even recall how many times I applied the clay [laughs].”As one point, Morikawa would think he had succeeded, only to nd that it didn’t work properly for a di erent fre-quency. Morikawa fought on with his clay in hand, trying to advance steadily in the cat-and-mouse game. It took him two years to arrive at the ideal coupler shape.“My clay turned out to be a power-ful weapon. Clay isn’t normally used in device prototype stages. But I’m con -dent in the veri cation using clay. We ultimately ensured symmetry and robustness inside the coupler using the materials that would be used in the n-ished product. Without clay, we might not have succeeded.”Up to that point, Rion had never deve loped a coupler with a wide fre-quency range of 1 Hz to 20 kHz and cal-culated uncertainty. e path Morikawa took was one no one had tried before. Looking back, he describes his achieve-ment as follows:“I still feel very honored to be involved in RACS, which is a big proj-ect. I’m proud that my coupler is being used not just in Japan, but in foreign countries, and that sound level meters and microphones calibrated with RACS are undoubtedly being used in various elds and research institutes. But the development of this coupler was a long, arduous struggle. I do want to take some time o to relax [laughs]. Although that doesn’t seem likely.” e RACS Project and Its Global In uence e Rion Service Center handles repairs and calibration of sound level meters and vibration meters on a daily basis. Toru Nishina, who works at the center, gave his evaluation of RACS.“RACS can perform calibrations di erences in the direction in which the devices faced when inserted. is issue remained unresolved in the initial stag-es of RACS development.“My predecessor reported poor rep-etition reproducibility when the devices were inserted facing in di erent direc-tions. But why this happened remained a mystery. So I inserted the devices end-lessly in lots of di erent ways, each time changing the structure of the acoustic coupler, to nd out how reproducible these measurements could be. At rst, I had no idea how to make any improve-ments. But with steady e ort, I gradual-ly identi ed where the problem lay. It took nearly two years to reach that point. Until then, my days were an end-less repetition of inserting a device into the coupler, checking measurements, considering and creating a new struc-ture, then going back to inserting the device. I never imagined the task would be so di cult.”What Morikawa nally identi ed was the need to ensure the symmetry and robustness of the internal structure of the acoustic coupler. An acoustic coupler has a passageway for air that lets the calibration sound from the sound source reach the microphone and keeps air pressure inside and out-side the coupler balanced. e lack of symmetry of this internal structure and the microphone structure was the cause of dispersions in the measurements observed when target devices were inserted facing in di erent directions. Results of measurements di ered sig-ni cantly when a device was measured inserted in one direction, then turned in another direction. ese dispersions would make it impossible to manage the performance of sound level meters and other instruments. From that point forward, Morikawa’s goal became ensuring the symmetry and robustness of the internal structure of the coupler with respect to the sound source, there-by ensuring reproducible measure-ments no matter how the target device was inserted.Clay, the Secret Weapon Behind the Innovative Results“Once, a while back, I used clay to verify sound leakage for the sound insulation performance improvement. Recalling this, I put clay on the RACS coupler, then performed a test, then put clay on another part for another test, and so forth. While repeating the tests in this way, there was a “Yes! I did it!” from 1 Hz to 20 kHz on a single system. It’s signi cantly reduced the number of processes we have to perform. Honestly, when I rst heard about the develop-ment e orts, I had my doubts a system like RACS could actually be developed. A system that handles the entire opera-tion in a single step? And even performs calibrations automatically? It was so innovative it didn’t seem possible. e major feature of RACS is that it comes equipped with all the functions neces-sary to obtain ISO/IEC 17025 accredita-tion. A system that is easy to use and yet still satis es those standards is invaluable.”RACS calibrates sound level meters, microphones and other instruments. It’s a system most people wouldn’t be familiar with. But it’s precisely these calibration systems that assure the per-formance of measuring instruments and guarantee the reliability of their measurements. e development of RACS, a system that supports society from behind the scenes, is de nitely one of Rion’s most impressive feats.5Toru NishinaEnvironmental Instrument Section, Custo-mer Support Group, Engineering Unit, Rion Service Center Co., Ltd. He was in charge of repairs and calibration of sound level me-ters, vibration meters, and other instru-ments and later involved in JCSS calibration in the Quality Assurance Department. He was instrumental in the acquisition of ISO/IEC 17025 accreditation for the RACS develop ment.
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