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Watching movies like "Fellinis Roma", "Alien" or "Apocalypse Now" on a 17" TV or computer screen is like listening to
Beethovens 7th Symphony on your radio clock. To get the real cinematographic feeling, a projector is essential.
Unfortunately those are very expensive, used ones are cheaper but very noisy. My Infocus LP420 sounds like a hair dryer.
Turning up the sound level may cover the noise, at least during action scenes, but may upset your neighbours very quick...
So I decided to construct a box, shielding the noise of the projector. I already saw something like this for dot-matrix
printers, and it worked so well that i was pretty impressed. The idea is to force the airflow, necessary to cool the
projector, through channels covered with damping material (acoustic foam). Those absorb the noise of the fans.
The whole inside of the box is covered with acoustic foam too. The light beam passes through a sheet of plexi-glas
(perspex), shielding the noise inside the box. The box is fairly big, for that reason its standing on the floor,
serving the secondary aim of a couch-table.
View from the top, without the top cover. Notice the air intake channel on the left. Red arrows indicate
the air flow.
The projector and the hush-box fan need to be mechanical isolated against the box. (structure-borne sound)
I use rubber structure-borne sound dampers, primarily intended to be used for RC cars/airplanes with combustive
engines. (Conrad Elektronik) Fan speed is adjusted by a constant voltage regulator (LM314), to achieve a compromise
between air flow and noise.