Reducing hearing by 10 dB will reduce a person's perception of speech sounds by:

The perception of speech sounds is closely tied to the decibel scale, which is logarithmic rather than linear. This means that a change in decibels does not translate to a straightforward percentage decrease in the perception of sound. A reduction of hearing by 10 dB generally correlates with a significant change in the listener's ability to detect and comprehend speech, often approximated to about a 50% reduction in overall sound perception, particularly with speech intelligibility.

The reason for this substantial impact is that most speech sounds are typically around 60-70 dB. So, if the hearing level drops by 10 dB, speech perception, which depends on the amplitude of sounds, may indeed feel like it has been halved. This is why choosing the response indicating a reduction by one half appropriately reflects how a 10 dB decrease affects the ability to perceive speech sounds.