The switching frequency has {TAIL ~ an audible frequency range} that results in unacceptable audible noise that is reduced by {HEAD ~ the present invention} 
The switching frequency has { TAIL ~ an audible frequency range } that results in unacceptable audible noise that is reduced by { HEAD ~ the present invention }
OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD