ADJ

great
increased, increasing
relative
The relative frequency of this illness in the area is of concern to all doctors
alarming
Bullets bounced off the rock with alarming frequency

VERB + FREQUENCY

decrease in, increase in
Crime increases in frequency in less settled neighbourhoods
decrease, increase, reduce
The drug can reduce the frequency and severity of attacks

PREP

with ~
Accidents of this sort are happening with increasing frequency

ADJ

high, low
ultrasonic
microwave, radio, television, vibration, wave
signal

FREQUENCY + NOUN

range
band