Apparatus and method to reduce noise emanating from a ventilation fan

Abstract

An apparatus and method for suppressing ventilation fan noise by covering fan blades and optionally duct with sound absorbing liner made out of soft flexible durable material such as felt. Another apparatus and method is encasing the fan unit in a sleeve made out of sound blocking, antivibration materials, such as mass loaded vinyl, rubber for housing portion, and sound absorbing materials, such as acoustic blankets for sleeve extension or combination of both. A preferred method includes covering the fan blades permanently or removably with felt liner in a way that the whole blade is covered and extra fringe material is trailing off the edge of the blades. The sound dampening casing includes duct case made out of mass loaded vinyl and rubber and the extension sleeve made out of sound absorbing material such as acoustic blanket. The sound dampening sleeve is flexible and can be folded or rolled away to save space for storage or transportation

What is claimed is: 
     
         1 . An apparatus for suppressing fan noise, the apparatus comprising:
 a fan blade sound-absorbing liner comprising soft, flexible durable material, attachable to blades of a fan; and   a housing sound-absorbing liner comprising flexible durable material and arrangeable to line an inside surface of a fan housing and optionally an air duct.   
     
     
         2 . An apparatus for suppressing ventilation fan noise transmitting with air blowing from a fan, the fan comprising at least one fan blade, the apparatus comprising:
 a sound-blocking and vibration-cancelling fan housing comprising non-resonant, elastic, flexible material, and   a sound-absorbing sleeve comprising flexible durable material and configured for attachment to the fan housing.   
     
     
         3 . A method for treating a fan to reduce emanating noise, the method comprising:
 attaching a non-resonant sound absorbing liner to blades of the fan, and   attaching the liner to an inside housing of the fan.   
     
     
         4 . A fan having fan blades operable to produce an air flow, wherein the fan blades are designed to have a soft sound-absorbing non-resonant surface and/or liner. 
     
     
         5 . The apparatus according to  claim 1 , wherein the sound absorbing liner has an adhesive surface. 
     
     
         6 . The apparatus according to  claim 1 , wherein the sound absorbing liner has a surface with a releasable attachment. 
     
     
         7 . The apparatus according to  claim 1 , wherein the sound absorbing liner attached to the fan blade has a trailing edge that can be straight, serrated or shaped otherwise. 
     
     
         8 . The apparatus according to  claim 2 , wherein the sound absorbing sleeve is flexible and/or foldable and/or rollable. 
     
     
         9 . The apparatus according to  claim 2 , wherein the sound absorbing sleeve comprises a flexible attachment configured to direct the air flow. 
     
     
         10 . The apparatus of  claim 2 , wherein the sleeve comprises a layered wall having a sound absorbing liner as an inner layer and an dense air tight shell as an outer layer. 
     
     
         11 . The method according to  claim 3 , wherein the attaching is by permanent adhesion to the blades and/or the housing. 
     
     
         12 . The method according to  claim 3 , wherein the attaching is releasable such as utilizing a hook and loop fastener. 
     
     
         13 . The fan according to  claim 4 , wherein the fan blade further comprises a plurality of filaments designed, structured and arranged to break air flow and/or reduce turbulence of the air flow. 
     
     
         14 . The fan blade according to  claim 4 , where it further comprises at least one soft edge, that can be in a serrated comb-like shape. 
     
     
         15 . The apparatus according to  claim 1 , wherein soft, flexible durable material comprises felt. 
     
     
         16 . The fan blade according to  claim 1 , where it further comprises at least one soft serrated comb-like edge. 
     
     
         17 . The fan according to  claim 1 , wherein the serrated comb-like edges are arranged with a trailing edge of the fan blade. 
     
     
         18 . The apparatus according to  claim 2 , wherein the soft, flexible durable material comprises rubber or mass-loaded vinyl. 
     
     
         19 . The apparatus according to  claim 2 , wherein the sleeve comprises an acoustic blanket 
     
     
         20 . The method according to  claim 3 , wherein the fan is a duct fan.