NCIDQ IDFX Practice Exam

Which rating is more closely related to the frequencies of speech?

1. Impact Insulation Class (IIC)

2. Sound Transmission Class (STC)

3. Noise Reduction Coefficient (NRC)

4. Speech Range Absorption (SRA)

The correct answer is: Speech Range Absorption (SRA)

The Speech Range Absorption (SRA) rating is specifically designed to measure how materials absorb sound frequencies that are primarily associated with human speech. This rating focuses on the critical band of frequencies where speech occurs, typically between 500 Hz to around 2000 Hz. By quantifying how effective a material is at absorbing these frequencies, SRA provides valuable insight into how well a space can minimize the transmission of speech, enhancing acoustic comfort and clarity within a room. In contrast, other ratings like the Impact Insulation Class (IIC) pertain primarily to the transmission of impact noise—such as footfalls—through building assemblies, rather than directly addressing speech frequencies. Sound Transmission Class (STC) measures how well a building partition attenuates airborne sound but encompasses a broader range of frequencies, not just those related to speech. The Noise Reduction Coefficient (NRC) indicates how well materials absorb sound across a range of frequencies but does not specifically relate to speech frequencies. Thus, among these options, SRA is the most closely related to the frequencies of speech, offering a focused perspective on the acoustic treatment necessary for effective speech intelligibility and comfort in an environment.