What is the defining characteristic of narrow band noise?

The defining characteristic of narrow band noise is that it is made up of a narrow range of frequencies. This means that within the spectrum of sound, narrow band noise is concentrated around specific frequency values, which distinguishes it from other noise types that might encompass a broader range of frequencies.

Narrow band noise is typically used in various applications, such as in hearing tests or acoustic measurements, because it allows for the assessment of how individuals perceive sound within these specific frequency ranges. This characteristic is significant for various tasks, including understanding the impacts of sound on health and the necessity for hearing protection in occupational settings, where certain frequencies may be more hazardous.

In contrast, low intensity does not define narrow band noise specifically, since both narrow band and wide band noises can have varying intensity levels. Additionally, the presence of wide band noise, which includes a broad range of frequencies, is fundamentally different from narrow band noise. Lastly, the reference to being less than 85 dB pertains to sound pressure levels but does not specifically relate to the type or characteristics of the noise itself. Therefore, the concentration of narrow band noise around a tight frequency range is the key aspect that defines it.