Silent device for air conditioning equipment

A silencer for an air conditioner, the silencer comprising:

• a first duct in a cylindrical shape at a noise outlet, the first duct including a reference microphone that detects noise as a reference signal;
• a speaker baffle on a top of the first duct, the speaker baffle having a circular shape as whole in a plan view and including a speaker around a center thereof;
• a back enclosure for the speaker, the back enclosure being on a back surface of the speaker baffle;
• a second duct that is in a shape of a cylinder and connected to a top of the speaker baffle;
• an error microphone in the second duct and above a diaphragm of the speaker at a distance to detect a control target signal that is an incompletely eliminated error signal;
• a cylindrical body for intake connected to a top of the second duct;
• a duct cover for enclosing an upper opening of the cylindrical body;
• and
• a gap that is between an inner circumferential surface of the first duct and an outer circumferential surface of the back enclosure for the speaker an serves as an acoustic path of noise to provide a plane wave, the noise being in a form of a first plane wave, the error microphone being configured to detect an error signal in the second duct, the speaker being configured to output a second plane wave with a phase opposite to a phase of the first plane wave.