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US 4,054,751 AGranted
Masking noise generator
AssigneeCDF Industries, Inc.
InventorsGeorge Donald Calder, John Duda, John Fatovic
Life of this patent
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Abstract
There is disclosed a masking noise generator which includes a digital means such as a shift register for generating noise signals wherein the output of the shift register is fed via a filtering means to a transducer means such as a speaker for converting the noise signals to acoustic waves.
Claims3
Apparatus for generating audible masking noise comprising:
- a multi-stage shift register having an input and at least two outputs connected to two different stages, an exclusive-or means having two inputs respectively connected to the outputs of said two stages and an output connected to the input of said shift register;
- means for generating shift pulses for shifting said shift register;
- a low-pass filter for passing signals only in the audio range, said low-pass filter having an input connected to one of the outputs of said multi-stage shift register and an output;
- a signal clipping amplifier means having an input connected to the output of said low-pass filter and an output;
- a spectral shaping filter having an input connected to the output of said signal clipping amplifier means and an output;
- and a loud speaker connected to the output of said spectral shaping filter.
3 more elements
Dependencies are inferred from the claim text.