| 381 / | HD | ELECTRICAL AUDIO SIGNAL PROCESSING SYSTEMS AND DEVICES |
| FOR 127 | DF | HEARING AIDS, ELECTRICAL (381/68) {15} |
| FOR 152 | DD | .~ Electromagnetic (e.g., dynamic) (381/192) {5} |
| FOR 162 | DD | .~.~ Specified diaphragm shape or structure (381/202) {2} |
| FOR 164 | | .~.~.~ Conical (381/204) |