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Inner window soundproofing

FACT: Windows are THE major conduit for the movement of outside noise into your home or office because the average window allows sound to travel through it easily.  When compared to an average exterior residential wall, a window allows 40 times more sound in than the wall does.

Noise Basics

To understand how and why ClimateSeal windows make your home or office quieter, we must review some of the basics of sound and sound transmission. 

Measuring Sound

Sound is made up of multiple frequencies.  Some frequencies in the high range like a whistle or a mosquito flying and some are very low like the thumping of a base drum or subwoofer portion of music.  The loudness of a sound (sound pressure) is measured in decibels (db).  The decibel scale is not linear but is logarithmic like the familiar Richter Scale for earthquakes.  On the decibel scale a sound that is measured at 60db is 10 times louder than a sound measured at 50db.

Decibel Readings for common sounds

Quiet room with air conditioner or heater on                     20db
Normal Conversation                                                             40db – 60db
Traffic on a busy street at 30 yards                                    80db – 90db
Jackhammer at 3 feet                                                            100db
Threshold of Pain                                                                   130 db

STC (Sound Transmission Class)

The STC number is a measure of how much sound is transmitted through an object like a wall or window.  It is a calculated number based on a weighted change in decibel level from one side of the object to the other side at 14 predetermined frequencies.  While different materials absorb different frequencies of sound a very different levels, the STC value gives you a single standardized number to compare the sound insulation of one product to another on an apples to apples basis.

Typical STC Values

             Single pane window                         25-27
             Double pane window                       26-30
             Residential Exterior Wall               43-45

STC numbers are based on the reduction of sound from the outside to the inside.  If the blend of 14 frequencies is 70db outside a window and is measured at 43db inside the window, the STC would be 27.  An STC of 27 represents the reduction of sound pressure that is 501 times quieter than the outside.  Seems terrific right?  However, a standard single pane window has an STC of 27 and we all agree that single pane windows muffle outside noise but would certainly say that they don’t make the room quiet.  Why?

Human Hearing

While 0db is the theoretical lower limit of human hearing, most people would say that a room with a sound level at 20 db was quiet.  But, it only takes a small increase of 1 or 2db for those same people to say the room was no longer quiet.  The reason why such a small change makes a large perceived difference is that, as it gets quieter, our hearing gets more sensitive.  That increased sensitivity, means that we often need to reduce noise levels not by just 501 times but by 10,000 times before people say that bothersome noise is not a problem anymore.  Hearing varies with individuals.  Sound that is bothersome to some might be at a frequency barely noticed by others.  Yes, hearing does deteriorate with age.

To make it even more complicated, we don’t hear all frequencies the same way.  Our ears are tuned to hear frequencies at the range of human voices (1000Hz to 5000Hz) at very low volume levels while we may not hear the high frequency of a mosquito flying past our ear at the same low volume level.  A study was conducted in 1930 by two scientists by the names of Fletcher and Munson that tested thousands of subjects to determine how loud a sound needed to be at various frequencies to have the subjects describe the sound as the same loudness.  This map of the sensitivity of the human ear became known as the “Fletcher-Munson” curves.  As an example, according to the study, sound at the very low frequency of 50Hz has to be played at a sound level of 85 decibels for the average person to perceive that sound to be the same volume a frequency of 1100Hz played at 20 decibels.  In other words, the 50Hz sound has to be played 3 Million times louder than the 1100Hz sound for people to say it is at the same volume.

How ClimateSeal reduces sound transmitted through a window.

When sound waves hit the exterior surface of the glass, some is reflected back outside, a very small amount is absorbed by the glass itself, and the rest exits the glass in multiple directions to be absorbed by the window frame and is attenuated by the distance to the listener.

ClimateSeal™ creates an insulating air gap and another hard surface which causes the sound waves to bounce around inside the cavity.  The larger the gap, the more attenuation is achieved.  The sound that does enter the acrylic panel is significantly absorbed due to the superior acoustical properties of acrylic vs. glass.

What can I expect?

Depending on the distance that the ClimateSeal window is mounted from the actual window, on average, customers can expect STC improvements on our standard 1/8” series from 27 on the plain window to between 34 and 37 (a reduction of  between 2500x and 5000x).  When our ¼” series is used, the STC improves to between 42 and 46 (a reduction of between 16,000x and 44,000x).  Keep in mind that STC improvements beyond 43 are usually not beneficial because the walls then become the more significant noise transmitter.

Is this going to solve your noise problem? 

Probably!  It has been proven to work for the last 30 years.  Click here to read the testimonials of people who have used ClimateSeal to make their home a quieter place.

If you have a noise problem that cannot be solved with STC reductions up to 46, the Acoustical Engineers at Acoustical Surfaces Inc. ( the manufacturer of ClimateSeal) specialize is high end recording studio and projection booth windows and can design a window to fit any demand.

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