Diagnostic audiometers generally provide one-third-octave masking noise bands for use in masking pure tones. This bandwidth is used because bands of that width

• A. Are centered in the frequency range of normal speech
• B. Produce more masking than pink noise does
• C. Encompass the width of a critical band
• D. Are less than the width of a critical band

Answer: (C)

Masking effectiveness hinges on the masker covering roughly the same frequency region that the auditory system uses to analyze a sound, known as the critical bandwidth. Using one-third-octave masking noise bands gives a practical approximation of that width across frequencies, so a pure-tone signal is masked efficiently without unnecessary energy spilling into adjacent frequencies. If the noise band were narrower than the critical band, parts of the tone could slip through the masker; if it were much wider, you would over-mask neighboring frequencies. Therefore, this bandwidth is chosen because it encompasses the width of a critical band.