Sound Insulation Testing

Need a sound test? Soundproof San Diego offers two forms of sound insulation testing, each one for a different type of sound transmission. Sound transmission can happen either in the air (airborne) or through the framework of the building (structural). In both cases, certified calibrated devices must be used for the measurements. Using phone apps (with built-in microphone) to measure sound levels can be a entertaining but are not calibrated accurately enough to provide usable results.

Airborne Insulation Testing (ASTM E90) is used to approximate the Sound Transmission Class (STC) of a partition (wall, ceiling, or floor) between two spaces. Outdoor/Indoor Transmission Class (OITC) is used exclusively when metering sound transmission through an exterior partition to the interior of the building. The most common setup to measure STC (or OITC) is to place a calibrated microphone in the receiving space and a specialized speaker in the source side. White noise is played through the speaker and the calibrated microphone will pick up the sound pressure levels that are transmitted through the partition. This data is used to calculate the measured STC (or OITC) rating of the target partition. This number will help to determine what modifications to the partition will be required in order to achieve desired sound insulation. Examples of airborne noises include speech, audio speakers (can be structural as well), etc. If you would like more information about STC & OITC ratings please click here.

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Impact Insulation Testing (ASTM E492) is used to measure transmission information when objects hit the structural components of a building. In order to test, a tapping machine (pictured above) is placed on the floor to simulate controlled foot steps. A metal hammer inside the unit sends taps through the structure (floor) and sound levels are measured in the area of concern (usually downstairs). The collected data is used to calculate the measured Impact Insulation Class (IIC). This number will help to determine what modifications to the partition will be required in order to achieve desired sound insulation. Examples of structural noises include footfall, dropping of object on the ground, closing or slamming of doors, etc. If you would like more information on IIC ratings please click here.


Acoustics Testing - Reverberation

Sound testing has proven to be very useful in the field of Acoustics. When sound is emitted in an enclosed space echoes tend to build up. This is known as reverberation. When the sound source is muted, the reverberation will continue to be heard as it is absorbed by the surroundings over time and the sound level decays. Reverberation testing setup requires both the source speaker and metering microphone to have open air space between them, usually by positioning both components in the same room.

The reverberation time (or RT60) describes the time it takes for the sound to decay by 60 dB after the sound source is muted. RT30 is the same as RT60 but instead meters the time it take for the sound to decay by 30 dB instead. The reverberation time of a space is affected by it’s dimensions, the building materials and installation methods used, and all objects (including people) within the room. Long reverberation times can make speech unintelligible, short reverberation times can make music sound dry or dead. The ideal reverb time depends on the size and intended use of the space as well as personal preference based on individual perception. This test is commonly used to determine how much acoustic treatment is needed to achieve the correct reverberation time. Materials can be tested to obtain a Noise Reduction Coefficient (NRC) when tested in a proper sound testing facility using this method.

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