Hambro® D500’s STC 57 is 70% more effective as an STC of 50 in reducing apparent loudness of transmitted airborne noise such as speech, radio, TV, music, etc. STC 50 is the minimum required by IBC. Higher STC ratings mean better sound control.
Independent tests in a completed apartment in accordance with ASTM-E336, as well as laboratory testing under ASTM-E90-70, resulted in Hambro receiving an STC 57 on bare concrete and a ½ inch gypsum ceiling assembly. Construction details for party walls, partitions, floor penetrations, doors, and windows are important when designing to achieve high STC ratings.
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IMPORTANT NOTE: Bare concrete or direct applied hard floor finishes generally do not provide adequate protection against the transfer of impact noise. It is recommended that a pliable, resilient, isolation underlayment be included wherever hard floor finishes such as ceramic tile or hardwood are used. The design professional should determine the overall requirements for the project and how the rating will be achieved. The Hambro assembly has an Impact Insulation Class (IIC) rating of 30 on bare concrete, similar to a solid 6 inch slab. Impact sound originates when one body strikes another, such as in the case of footsteps, hammering and objects falling. The IIC of any assembly is strongly dependent on the floor finishes and underlayments.
Under the International Building Code (IBC), the minimum standard for IIC is 50. Transmission of impact sound can be controlled by isolation and absorption. Typical materials used for absorption are: pad and carpet, cork, rubberized mats, etc. It is important to note that unless the opposite surfaces of the assembly (floor and ceiling) are isolated, sound travels through the connecting structure. This is because impact sound travels through the structure with little loss of energy if the structure is continuous and rigid. Hambro’s IIC with soft vinyl is 55, and with pad and carpeting it increases to 69. The most important consideration for a better IIC rating is the type of floor covering used.
All bare structural floor systems do not meet IBC’s minimum IIC rating of 50. To achieve an IIC rating of 50 or more, an underlayment/substrate material is suggested to isolate the structural floor from hard surface flooring.