http://monoadc.blog64.fc2.com/blog-entry-119.html
https://www.youtube.com/watch?v=Dtb-eAP7IxQ
http://blog-imgs-52-origin.fc2.com/m/o/n/monoadc/Insertion_depth_ER-4S.png
http://blog-imgs-52-origin.fc2.com/m/o/n/monoadc/Insertion_depth_MA850GB.png
http://blog-imgs-52-origin.fc2.com/m/o/n/monoadc/Insertion_depth_AURVANA_In-Ear2.png
http://blog-imgs-50-origin.fc2.com/m/o/n/monoadc/Fitting_FR.png