| 381 / | HD | ELECTRICAL AUDIO SIGNAL PROCESSING SYSTEMS AND DEVICES |
| FOR 127 | DF | HEARING AIDS, ELECTRICAL (381/68) {15} |
| FOR 140 | DD | .~ With acoustic wave modifying structure (381/153) {5} |
| FOR 145 | | .~.~ Absorbing or attenuating element (e.g., baffle, obstruction, damping) (381/158) |