A special device can transmit sound out of phase from a noisy jackhammer to its op- erator using earphones. over the noise of the jackhammer, the operator can easily hear your voice while you are unable to hear his. why?1. these devices reduce jackhammer noise by using destructive interference to cancel the noisy sound, so he can hear your voice clearly.2. the operator's earphones are connected to your microphone, so he can hear your voice clearly.3. the operator's earphonex amplifies your voice, so he can hear your voice clearly.4. the operator's earphones change the fre- quencies of your voice, so he can hear your voice clearly.