Archive for March, 2012

Reducing noise transmission into the kitchen

Monday, March 26th, 2012

Reducing noise transmission into the Kitchen

Noise in the kitchen can also come from outside the home – traffic, noisy neighbors, air conditioner units, or from noisy rooms such as laundry rooms, which are adjacent to the kitchen.   In order to provide good barriers to noise in adjacent rooms or outside, you will need to know how well a material resists transferring sound, and which combinations of materials will provide the best reduction in noise transmission. 

A material’s resistance to transferring sound is rated by STC (Sound Transmission Class).  The higher the STC rating, the more noise is blocked from transmitting through the material.  The STC rating is usually an average over 125Hz – 4000 Hz, and can vary greatly over a range of frequencies.  Graphs showing the STC rating by frequency are sometimes available for a material, and will help you in choosing a material based on the sound you are trying to block.  Shown below are some STC examples:

STC 30 – normal speech audible

STC 40 – loud speech audible

STC 50 – shouting barely audible

STC 60 – loud speech should not be audible

The most important means of blocking sound transfer is to first seal all holes where sound might “leak” through (flanking noise).  Just like water will leak through the tiniest crack, sound will travel through the weakest points – holes, outlets, doors, windows, etc…  Use silicone caulk (wherever you won’t be painting) around outlets, windows, doors, and between the bottom of the drywall and the floor.  If the drywall has been removed from an exterior wall, caulk along the siding and 2×4 framing.   

The next weakest area, are usually the windows and doors.  A typical single pane window has a STC of 25 and a double pane window has a STC of 30.  If you are purchasing new windows, consider an acoustic window (STC 45 – 60), or a window with laminated glass (STC 35).  You can also retrofit an existing window with an additional laminated pane (STC 44-48 for dbl pane).  If you have a hollow core door, you can improve your STC rating from 15 to 30 by replacing it with a solid core door or an acoustic door.



If you are doing new construction or remodeling down to the studs, here are some things that you can do to reduce the sound transmission:

STC       Construction technique (5/8” drywall and bat insulation)

39         Regular studs with one sheet of drywall on each side

47         Staggered studs with one sheet of drywall on each side

 53         Staggered studs with drywall on one side and 2 sheets of drywall on other side

 56         Staggered studs with double layer of drywall on each side

 56         Regular studs with resilient channel and double layer of drywall on each side

 60         Double studs with drywall on one side and 2 sheets of drywall on the other side

 63         Double studs with double layer of drywall              

If you don’t have the room for any of the above options, you might consider using quietrock.


If your HVAC system is contributing noise to your kitchen from either the outside compressor or the furnace blower, you might consider some of the following measures:

1.     Move the compressor to another location outside of the house

2.     Install Acoustiblok all weather sound panels around compressor unit


3.     Have a compressor noise absorbing jacket  installed 


4.     install vibration isolation mounts for blower unit or on base of furnace


5.     install a vibration break in the duct adjacent to the fan

6.     Install duct liner or use flexible ducts

Personal Experience – Where I had blower noise coming out of the ductwork, I replaced the rigid metal duct from the trunk duct to the vent boot with a flexible insulated duct.  This worked well for me.  Check




Kitchen Noise – Acoustics

Monday, March 19th, 2012

Kitchen Noise – acoustics  

Have you ever noticed how loud even the slightest noises are in a large empty room with lots of hard surfaces?  That’s because all the noise is reflected in the room, resulting in high reverberation times, which makes the perceived noise level higher.  Reverberation in a room is directly related to room volume and inversely related to the total absorption in a room. 

Absorptive materials reduce sound reflection and the NRC (noise reduction coefficient) rating indicates how much of the sound is absorbed by the material.  An NRC rating of .75 indicates 75% of sound that contacts it is absorbed, and 25% of the sound that contacts it is reflected.   The NRC rating can vary greatly over a range of frequencies, and will be less absorptive for lower frequencies. 

Here are some sample nrc ratings:

Granite  –   .00  (no absorption)

Drywall  –   .05   (5% absorption)

Heavy drapes  –  .60  (60% absorption)

Wood furniture  –  .30  (30% absorption)

Fabric upholstered seating  –  .60  (60% absorption)

Heavy carpet on pad  –  .30 – .55 (30% – 55% absorption)

Acoustical ceiling tiles  –  .50 – .70 (50% – 70% absorption)

As you can see, soft porous materials absorb sound, so consider using things like soft overstuffed furniture, thick carpet and padding in the living area, area rugs, or thick curtains with a tight weave.  Also consider using acoustical art panels, which can have any image printed on them and hang like art.   If acoustic tiles are too commercial looking, and not in keeping with the kitchen décor, consider a stretch ceiling for a high end European look.


Kitchen ventilation hoods – noise

Monday, March 12th, 2012

Kitchen ventilation hoods – noise


Although there are other factors to choosing a vent hood, this article will focus on selecting a quiet vent hood. 

Although the noise level ratings for dishwashers are in decibels (db), vent hood noise level ratings are in sones.  A table showing an approximate equivalent rating is as follows:

Sones       Decibels     Equivalent sound

.5sones       30db         whisper

1 sone         40db         quiet conversation

2 sones       50db          moderate rainfall

4sones        60db           normal conversation

8sones        70db           street noise

9sones+                          Home Ventilating Institute recommends not buying


Factors that determine how loud a vent hood will be:


  1. Blower used – most half decent range hoods today use pretty good blowers, but an inline blower in the attic with a duct silencer will definitely be quieter than an internal blower. 
  2. Probably the next most important factor contributing to range hood noise is duct issues – too small, too many bends, or just badly installed.   No matter what brand of range hood you choose, use as large a duct as possible (10” if possible).  A larger duct will allow you to run the blower at a slower speed to move the same amount of air.  If the blower is an inline blower on the roof or in the attic, make sure the duct is at least 6 feet long to minimize blower noise.  However, if the blower is internal, use as short a length of ductwork as possible, with as few bends as possible.  As the size of the duct decreases, and the length and number of bends increases, the noise level will increase because of the increase in static pressure (pressure against which the fan moves air). 
  3. Another critical element in a well designed range hood structure is where the air is getting pulled through the filters.  Air passing through a baffle filter will generally be quieter than a mesh filter.  The greater the area covered in he bottom of the hood, the quieter it should be.   If the inside of the hood behind the filters has a lot of projections, this can also cause some air turbulence noise.  
  4. More CFM = more noise.  Don’t just get the biggest, baddest blower you can.  A 1200 CFM internal blower vent on high can easily be in the 6-8 sones range (See chart above), so it’s critical to match the blower to the ducting, to the btu output of the range and to the range hood size.   For every 10,000 BTU of burner capacity, you will need 100CFM.  Therefore a 80,000 BTU range will need 800 CFM.  If you really have your heart set on that commercial high BTU range, then you will obviously have a noisier vent. 
  5. Consider the size and placement of the hood.  According to research by the University of Minnesota, many range hoods are too small, too high, or not oriented properly to do the job.  This means that the vent is then run at a higher CFM than necessary and is therefore louder.  Hoods should be at least as wide as the range, and no more than 24 inches above the cooking surface (islands typically 27 inches), and project out 20 inches.
  6. Also consider the placement of the exterior hood.  Is the vent directed towards a noisy area such as an air conditioner or a noisy street, which will transmit those noises back into your kitchen?  If so, consider running the vent through a different location (roof vs. wall), or using a back draft damper to help reduce the noise.

Most vent manufacturer websites will show the sones by CFM speed for each of their models.  Maybe in a future article, I’ll  compile a list of brands/models by sones. 

Kitchen Noise – misc appliances

Monday, March 5th, 2012



Kitchen Noise – misc appliances

Garbage Disposal

Things to look for in getting a quieter disposal:

1.     Insulation around the shroud, obviously the more the better

2.      Rubber mounting to isolate the vibration from the sink and drain pipe

3.      Drain cover(batch) or rubber baffle(continuous feed)  The rubber baffle not only helps keep it quiet when you grind up food, but also helps keep it quiet when your dishwasher drains.

4.     Type of sink – cast iron is quieter than a cheap stainless sink.

Some sound comparisons:

Personal Experience – I have an Insinkerator Evolution Excel.  It’s the quietest disposal I’ve owned.  When just running water with it on it is very quiet (like the commercial).  When grinding food, this is about as quiet as you can expect for this noisy appliance. 


Appliances – Hot Water Dispensers

Hot Water Dispensers can be surprisingly noisy (rumbling noise) as they heat up the water.

 Personal Experience – I had an Insinkerator SST-FLTR, which was quite noisy when it was heating water.  I replaced it with a Waste King hot water dispenser and water chiller.  The hot water dispenser was much quieter, but the chiller was noisy. 


Appliances – Stoves/Ovens/Cooktops

Surprise….ovens can be noisy!  That little cooling fan for the electronic controls on some ovens can end up being louder than your fridge.  Drop in ranges and stoves with the controls in the back, and some higher end wall ovens seem to have fewer (if any) complaints about noise.  Induction cooktops can have a light popping, humming, or clicking noise with a burner on high, which most people don’t seem to mind.  Selection of good induction cookware will reduce or eliminate the noise coming from an Induction cook top.  Just because the cookware is Induction compatible, doesn’t mean it’s the most efficient.   I’ve found that enamel steel, carbon steel, or cast iron cookware work the best for an Induction cooktop .  Think about it.  Since magnetism is what heats the cookware, the more iron/steel content, the faster it heats, and actually the less noise it makes. 

Personal experience – I have an Electrolux induction cooktop (Kenmore Elite), and tested steel enamel cookware (Chantal) and carbon steel cookware against Induction compatible cookware, and was surprised by the difference is how quiet the cook top was, and how much faster things heated up.