Active noise reduction device for electronic apparatus

An active noise reduction device for reducing noise in an electronic apparatus having a casing, the casing having an interior, and at least one element producing noise in the interior of the casing, said device comprising:

• a duct adapted to be mounted on the casing of the electronic apparatus and having at least one air passage therein, said at least one air passage having a first opening in communication with the interior of the casing and a second opening;
• first detecting means arranged in the duct near the first opening for detecting sound;
• a controllable source of sound arranged in the duct near the second opening for producing sound to be superimposed on the noise introduced in the duct via said first opening;
• second detecting means arranged in the duct near the second opening for detecting sound;
• and
• means for controlling the controllable source of sound in response to outputs of said first and second detecting means thereby to reduce the noise produced in the casing of the electronic apparatus,
• wherein said first and second detecting means comprise microphones, and said controllable source of sound comprises a speaker, and
• wherein said duct comprises a plurality of passages arranged in parallel with each other, each of said passages including respective said first and second detecting means and respective said controllable source of sound.

An electronic apparatus comprising:

• a casing having an interior;
• at least one electronic component arranged in the casing;
• at least one cooling fan arranged in the casing for cooling the at least one electronic component and producing noise in the casing interior;
• an active noise reduction device for reducing the noise produced in the casing by the at least one cooling fan, said active noise reduction device comprising:
• a duct mounted on the casing of the electronic apparatus, the duct having at least one air passage formed therein, said at least one air passage having a first opening in communication with the interior of the casing and a second opening;
• first detecting means arranged in the duct near the first opening for detecting sound in the casing interior;
• a controllable source of sound arranged in the duct near the second opening for producing sound to be superimposed on the noise introduced into the duct via said first opening;
• second detecting means arranged in the duct near the second opening for detecting sound;
• and
• means for controlling the controllable source of sound in response to outputs of said first and second detecting means for reducing the noise produced in the casing,
• wherein said duct is adjustable thereby to vary the length of the at least one passage, and
• wherein said duct comprises a first duct unit adapted to be mounted on the casing of the electronic apparatus and having the first opening in communication with the interior of the casing and a second duct unit slidably coupled to the first duct unit and defining therewith the at least one passage.

An electronic apparatus comprising:

• a casing having an interior;
• at least one electronic component arranged in the casing;
• at least one cooling fan arranged in the casing for cooling the at least one electronic component and producing noise in the casing interior;
• an active noise reduction device for reducing the noise produced in the casing by the at least one cooling fan, said active noise reduction device comprising:
• a duct mounted on the casing of the electronic apparatus, the duct having at least one air passage formed therein, said at least one air passage having a first opening in communication with the interior of the casing and a second opening;
• first detecting means arranged in the duct near the first opening for detecting sound in the casing interior;
• a controllable source of sound arranged in the duct near the second opening for producing sound to be superimposed on the noise introduced into the duct via said first opening;
• second detecting means arranged in the duct near the second opening for detecting sound;
• and
• means for controlling the controllable source of sound in response to outputs of said first and second detecting means for reducing the noise produced in the casing,
• wherein said first and second detecting means comprise respective microphones, and said controllable source of sound comprises a speaker, and
• wherein said duct comprises a plurality of passages arranged in parallel to each other, and said electronic apparatus further comprises plural ones of said first and second detecting means and said plural controllable sources of sound respectively associated with and disposed in said plurality of passages.