| 摘要 |
Provided is an acoustic conversion device for active noise control that enables unintended shifting of the phase of sound emitted from a speaker unit to be effectively prevented by preventing fluctuations in the lowest resonance frequency of the speaker unit by preventing intrusion of water and foreign matter into a speaker unit diaphragm, etc., thereby effectively suppressing or eliminating noise. A protective member (4) completely conceals an opening (O), so all water and foreign matter passing through the opening (O) will reach the upper surface of the protective member (4). Furthermore, the protective member (4) completely conceals the speaker unit (2), so the diaphragm (21) of the speaker unit (2) can be protected against water and foreign matter falling from the protective member (4). Consequently, adhesion of water and foreign matter to the diaphragm (21) is prevented, fluctuations in the lowest resonance frequency can be prevented, and emitted sound is thus made unlikely to shift out of phase from the opposite phase of noise, thereby enabling noise to be effectively suppressed or eliminated. |
