Reducing audible noise in stereo receiving

DETAILED DESCRIPTION We claim: 1.
A receiver for receiving a stereophonic signal with upper and lower sidebands carrying a modulating audio signal, said receiver comprising, independent sideband circuitry for providing upper and lower sideband signals, selector circuitry responsive to the level of audible noise in each said upper and lower sideband signal for selecting that one of said sideband signals having a lower level of audible noise relative to the other, an ISB highpass filter for filtering said that one of said sideband signals and producing a highpass filtered sideband signal, stereo detector circuity for providing left and right stereophonic audio signals, at least one audio lowpass filter for filtering each said left and right stereophonic audio signals and producing corresponding lowpass filtered left and right stereophonic audio signals, and at least one signal combiner for combining said highpass filtered sideband signal with each said lowpass filtered left and right stereophonic audio signals to produce corresponding composite left and right audio signals.
2.
The receiver as claimed in claim 1, wherein said selector circuitry comprises, prefilter circuits responsive to said upper and lower sideband signals for providing corresponding upper and lower sideband quality signals representing the level of audible noise present in said upper and lower sideband signals respectively, a signal comparator responsive to the level of said upper and lower sideband quality signals for providing a logic control signal having one of at least two states representative of that one of said sideband quality signals having a signal level greater than the other, and a switch for providing one of said upper and said lower sideband signals in response to the state of said logic control signal.
3.
The receiver as claimed in claim 2 wherein said prefilters comprise high-Q bandpass filters centered at a frequency corresponding to the separation between carrier frequencies of adjacent channels.
4.
The receiver as claimed in claim 2 wherein said switch comprises a crossfade circuit