The Impact of a Poorly Isolated Floor


Do you need an IIC test?

Do your tenants complain of hearing their neighbors above?  Does your old building meet modern building codes for sound isolation?  Do you want to make sure that you have the sound isolation that you paid for?  Maybe you need an IIC test.

What is an IIC rating?

The IIC (Impact Insulation Class) is a rating of the impact sound on a floor that is audible in the room below.  A higher number means better impact sound insulation.

What is an IIC test?

An IIC test is done by an acoustic engineer using ASTM Standard E1007 - Standard Test Method for Field Measurement of Tapping Machine Impact Sound Transmission Through Floor-Ceiling Assemblies and Associated Support Structures.   The test can determine the IIC of the floor-ceiling that separates condominiums, apartments, or offices.

How is an IIC test done?

The test requires access to the both rooms – the one above the floor and the one below.  A standard tapping machine bangs on the floor to generate impact sound (see ours in action).  First, while the tapping machine is banging away, the sound level is measured in the room below.  This is repeated with the machine in four different positions on the floor.

Then the reverberation time, or T60, is measured in the room below.   The T60 is used in IIC calculation to “normalize” the measurements to a standard condition.  This allows us to compare an IIC measured in a “dead” room to one measured in a “live” room.

Next, the airborne sound isolation of the floor-ceiling is measured.  Usually a loudspeaker and amplifier generate pink noise in the room below and the sound levels are measured above and below.  This done to make sure that the impact sound measured below is not “contaminated” by airborne sound transmission.

Finally, the “background” noise level noise is measured.  Background noise is sound that is present in the room below from traffic outside, the air-conditioning, or other activity in the area.  If there is too much background noise, sometimes we have to test at night or at another time when the background noise is quieter.

After the noise testing is done, the AIIC (formerly known as the FIIC) is calculated using ASTM Standard E989 Classification for Determination of Impact Insulation.  I will explain more about IIC, AIIC, and FIIC terms in a future post.

How long does the sound test take?An IIC test usually takes one to two hours, so if you are planning to have us do the test, please allow two hours.