Electronic siren audio notch filter for transmitters
First Claim
1. An audio comb notch filter system adaptable to receiving a composite signal comprising at least a first signal and a second signal and notching out the fundamental frequency and one or more harmonics thereof of said first or second signal comprising:
- a. first means for generating a ramp signal;
b. Second means responsive to said ramp signal for controlling a comb notch filter for notching out the fundamental and one or more harmonics of one of said signals.
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Accused Products
Abstract
A notch filter as disclosed which is adaptable to notching out a background siren from voice communications from an emergency vehicle. Two embodiments are disclosed. In the first embodiment, a frequency lock loop tracks the fundamental frequency of an electronic siren. The siren fundamental frequency is then notched out from voice transmissions using a notch filter. In the preferred transmissions using a notch filter. In the preferred embodiment, a digital ramp is generated by a first digital signal processor. This signal is input to an amplifier and a speaker thus producing an electronic siren. The digital ramp is also input to a second digital signal processor which notches out the fundamental frequency and odd harmonics thereof from the digital ramp thus acting as a comb notch filter. Analog voice is digitized by way of an analog to digital converter and input to the second digital signal processor. The second digital signal processor combs out the fundamental frequency and odd harmonics of the background siren signal from the digitized voice signal. The digitized voice signal is then converted back to an analog signal by way of a digital to analog converter.
45 Citations
16 Claims
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1. An audio comb notch filter system adaptable to receiving a composite signal comprising at least a first signal and a second signal and notching out the fundamental frequency and one or more harmonics thereof of said first or second signal comprising:
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a. first means for generating a ramp signal; b. Second means responsive to said ramp signal for controlling a comb notch filter for notching out the fundamental and one or more harmonics of one of said signals. - View Dependent Claims (2, 3, 4)
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5. An electronic siren and audio comb filter for use in emergency vehicles for notching out background siren sounds from voice transmissions comprising;
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first means for generating a digital signal; amplifier means electrically coupled to said first means for amplifying said digital signal; speaker means coupled to said amplifier means for converting said digital signal to an audible sound; second means having an input means and output means and adapted to receive a composite signal at said input means comprised of said digital signal and a second signal, said second means being operatively coupled to said first means and responsive thereto for notching out the fundamental frequency and one or more harmonics of said digital signal from said composite signal. - View Dependent Claims (6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16)
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Specification