Stereo sound reproducing apparatus with noise reduction

Stereo audio apparatus having input means having at least two input channels carrying audio frequency input signals with one of the input channels having signals with a noise level substantially less than that on other channels, and having at least two audio frequency signal output terminals to which are fed audio output signals derived from the input signals wherein there are provided controllable means including a frequency selective filter and signal level controller controlling the output from the frequency selective filter in accordance with an applied control signal for introducing cross-talk at the higher frequency end of the audio frequency band between output signals to the output terminals, control means including a high pass filter and rectifier arranged to receive the signal on that one of said input channels having the lower noise level to produce a control signal and means for applying said control signal to said signal level controller to be operative on said controllable means to increase the cross-talk as the signal level decreases.

Radio receiving apparatus for receiving frequency modulated signals carrying stereo programmes using difference signals on a pilot carrier wherein there are provided means for demodulating the received signals to provide audio frequency input signals and decoding means for providing separate audio frequency signal outputs wherein there are provided controllable means including a frequency selective filter and adjustable signal level controller operably responsive to an applied control signal for introducing cross talk at the higher frequency end of the audio frequency band between the audio frequency output signals and means including a high pass filter and rectifier arranged to receive at least one of the audio frequency signals to provide a control signal dependent on the amplitude of said at least one of the audio frequency signals, and means applying said control signal to said adjustable signal level controller to increase the cross talk at the higher frequency end of the audio frequency band as the signal level decreases.