"Specific frequencies" refers to particular sound waves or signals that have a distinct pitch or tone, different from other frequencies. Full definition
It is based on experimental physics showing resonance of the molecule at specific frequencies. (judithcurry.com)
These gases absorb specific frequencies of infrared radiation — heat — that would otherwise escape into space. (newscientist.com)
The system analyses the noise level inside the vehicle by means of a microphone and makes selective adjustments to its output signals in specific frequency ranges. (thetorquereport.com)