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