Why do 500 and 1000 Hz have lower allowable ambient noise levels in screening?

Why do 500 and 1000 Hz have lower allowable ambient noise levels in screening?

• A. Because high-frequency noise is more distracting
• B. Because of upward spread of masking/excitation
• C. Because 500/1000 Hz are not important
• D. Because equipment is less sensitive at those frequencies

Answer: (B)