Universal Testing & Research Center (Division of Sustainable Stewardship Private Limited), an ISO 17025:2017 certified Laboratory approved by BIS, NABL and QAI.Sound Transmission Class (STC) testing is a standardized method used to measure the sound insulation or sound-blocking capabilities of building materials, partitions, and structures. The STC rating is an important metric that helps quantify how well a material or assembly reduces the transmission of airborne sound. The higher the STC rating, the better the sound insulation.

• Test Setup:
  STC testing is typically performed in a laboratory or specialized facility designed for acoustical testing. The test setup involves constructing a partition or assembly that includes the material being tested. This assembly is installed between two soundproof rooms.
• Sound Source:
  A calibrated sound source, often referred to as the "pink noise generator," is placed in one of the rooms. Pink noise is a type of random noise with equal energy per octave, simulating a broad range of frequencies.
• Microphones:
  Microphones are strategically placed in both the source room and the receiving room to measure the sound levels. These microphones record the sound pressure levels before and after passing through the test material.
• Frequency Analysis:
  The sound is transmitted through the test material at various frequencies. The sound pressure levels are measured across a range of frequencies to analyze how well the material attenuates sound at different pitch levels.
• Calculation of STC Rating:
  The STC rating is calculated based on the measured sound reduction at various frequencies. The STC rating is determined by comparing the sound transmission loss of the test material to standard reference curves.
• STC Curve:
  The STC rating is represented graphically on an STC curve, which shows the sound transmission loss across different frequencies. This curve provides a visual representation of the material's performance in blocking sound.
• Standardized Reference:
  STC testing is conducted following the procedures outlined in ASTM E90 (for laboratory measurements) or ASTM E413 (for field measurements). These standards provide detailed guidelines for test conditions, instrumentation, and calculations.
• Results and Certification:
  Once the testing is complete, the STC rating is assigned to the tested material. This rating is often used for product certification and labeling to provide consumers with information about the material's sound insulation properties.

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