Certainly! When it comes to understanding the acoustical properties of building materials and systems, two of the most commonly referenced ratings are the Sound Transmission Class (STC) and the Impact Insulation Class (IIC). These ratings provide valuable insights into how well a building component or assembly can block or insulate against sound.
**1. Sound Transmission Class (STC):**
- **Definition**: STC measures the ability of a wall, ceiling, door, or window to reduce airborne noise, such as voices, TV, music, and other common interior noise sources.
- **Testing Method**: A standardized noise source is played on one side of the partition, and the noise level is measured on both sides. The difference in sound levels, adjusted for the frequencies of normal human speech, gives the STC rating.
- **STC Ratings**:
- **20-25**: Poor; most normal speech can be easily understood.
- **30-35**: Fair; loud speech is understood, normal speech is audible but not easily understood.
- **40-45**: Good; loud speech is audible but not easily understood.
- **50-60**: Very good; loud speech is barely audible.
- **60+**: Excellent; most sounds are inaudible.
- **Applications**: Commonly used to evaluate the effectiveness of interior walls, ceilings, floors, doors, and windows.
**2. Impact Insulation Class (IIC):**
- **Definition**: IIC measures a floor/ceiling assembly's ability to reduce impact noise, such as footsteps or dropped objects. It's particularly significant in multi-story buildings.
- **Testing Method**: A "tapping machine" with five hammers tapping in a consistent pattern is used to simulate footfalls. Noise levels are measured in the room below. The difference between the noise produced by the machine and the noise in the room below gives the IIC rating.
- **IIC Ratings**:
- **20-30**: Poor; even soft footsteps are quite audible.
- **30-40**: Fair; soft footsteps are heard, hard footsteps or dropped objects can be disturbing.
- **50+**: Good; impact noises are heard faintly, if at all.
- **Applications**: Used for floor/ceiling assemblies to assess the effectiveness of underlayments, carpets, and other floor finishes in reducing impact noise.
**Other Important Notes:**
- **Field vs. Lab Ratings**: It's important to note that both STC and IIC have lab (ASTC and AIIC) and field (FSTC and FIIC) measurements. Lab measurements tend to be higher as they're taken in controlled environments, while field measurements might be lower due to real-world variables.
- **Frequency Matters**: Both STC and IIC are weighted averages across a range of frequencies. Therefore, an assembly might perform differently at low versus high frequencies, even if it has the same average rating.
- **Limitations**: STC and IIC are valuable metrics, but they don't tell the full story of an assembly's acoustic performance. Consider other factors such as flanking paths (where sound bypasses the primary barrier), low-frequency performance, and the specific needs of the environment.
In summary, STC and IIC ratings provide guidelines to gauge the sound-reducing capabilities of building materials and assemblies. They're important for architects, builders, and homeowners who want to ensure a quieter, more peaceful environment.
**1. Sound Transmission Class (STC):**
- **Definition**: STC measures the ability of a wall, ceiling, door, or window to reduce airborne noise, such as voices, TV, music, and other common interior noise sources.
- **Testing Method**: A standardized noise source is played on one side of the partition, and the noise level is measured on both sides. The difference in sound levels, adjusted for the frequencies of normal human speech, gives the STC rating.
- **STC Ratings**:
- **20-25**: Poor; most normal speech can be easily understood.
- **30-35**: Fair; loud speech is understood, normal speech is audible but not easily understood.
- **40-45**: Good; loud speech is audible but not easily understood.
- **50-60**: Very good; loud speech is barely audible.
- **60+**: Excellent; most sounds are inaudible.
- **Applications**: Commonly used to evaluate the effectiveness of interior walls, ceilings, floors, doors, and windows.
**2. Impact Insulation Class (IIC):**
- **Definition**: IIC measures a floor/ceiling assembly's ability to reduce impact noise, such as footsteps or dropped objects. It's particularly significant in multi-story buildings.
- **Testing Method**: A "tapping machine" with five hammers tapping in a consistent pattern is used to simulate footfalls. Noise levels are measured in the room below. The difference between the noise produced by the machine and the noise in the room below gives the IIC rating.
- **IIC Ratings**:
- **20-30**: Poor; even soft footsteps are quite audible.
- **30-40**: Fair; soft footsteps are heard, hard footsteps or dropped objects can be disturbing.
- **50+**: Good; impact noises are heard faintly, if at all.
- **Applications**: Used for floor/ceiling assemblies to assess the effectiveness of underlayments, carpets, and other floor finishes in reducing impact noise.
**Other Important Notes:**
- **Field vs. Lab Ratings**: It's important to note that both STC and IIC have lab (ASTC and AIIC) and field (FSTC and FIIC) measurements. Lab measurements tend to be higher as they're taken in controlled environments, while field measurements might be lower due to real-world variables.
- **Frequency Matters**: Both STC and IIC are weighted averages across a range of frequencies. Therefore, an assembly might perform differently at low versus high frequencies, even if it has the same average rating.
- **Limitations**: STC and IIC are valuable metrics, but they don't tell the full story of an assembly's acoustic performance. Consider other factors such as flanking paths (where sound bypasses the primary barrier), low-frequency performance, and the specific needs of the environment.
In summary, STC and IIC ratings provide guidelines to gauge the sound-reducing capabilities of building materials and assemblies. They're important for architects, builders, and homeowners who want to ensure a quieter, more peaceful environment.
Leave a comment
This site is protected by hCaptcha and the hCaptcha Privacy Policy and Terms of Service apply.