Thanks to Akutsu-san and his company,

Concerning the oplev issue reported in klog#9681, klog#9855 and so on;

• It was found that the noise level at about 1 to 7Hz was improved by modifying the air-shield structure (Figure 1).
  • It seems so far there was some small hoels on the structure, and they were covered in this time.
  • A quick test was done this time.
• Building a better air-shielding system again is necessary, as the first step. Doing that could improve the noise level more. to be investigated (figure2, after the work, with smaller band width).