| Patent Number |
Title Of Patent |
Date Issued |
| 6937912 |
Anti-aliased clipping by band-limited modulation with step functions |
August 30, 2005 |
| A method for computing the "clippings" of an audio signal in the digital domain to prevent aliasing is disclosed. An offset signal is found by subtracting a threshold from samples of the audio signal. These are multiplied by a pulse after the pulse is lined up in time with the crossi |
| 6618486 |
Controller for FM 412 multiplex power regulation |
September 9, 2003 |
| A feedback controller, embedded in an FM audio processor, that controls the "integrated multiplex power" to the requirements of ITU-R 412 (2.51) is disclosed. This regulation specifies the maximum power, which is the same as the power produced by a sinewave modulating the carrier .+-.19 |
| 6434241 |
Controlling the peak levels of the FM composite signal by half-cosine interpolation |
August 13, 2002 |
| A method for controlling the peak levels of an FM composite signal is described. First, the FM signal is clipped to obtain an error signal. This signal comprises the "clippings" resulting from the clipping operation. Next, the peaks of the error signal are determined. Then, a half-cosine |
| 6337999 |
Oversampled differential clipper |
January 8, 2002 |
| A digital clipper is highly oversampled to decrease aliasing and increase accuracy. The difference between the clipper's input and output is then downsampled and added to the delayed, unclipped signal at 1.times. sample rate to achieve clipping. Filters operating at 1.times. can be place |
| 5574791 |
Combined de-esser and high-frequency enhancer using single pair of level detectors |
November 12, 1996 |
| Two level detectors with logarithmic outputs receive an input audio signal. The first level detector receives the signal through a high-pass filter while the second level detector receives the signal through a band-pass filter contoured to simulate the equal-loudness curves of the human |
| 5444788 |
Audio compressor combining feedback and feedfoward sidechain processing |
August 22, 1995 |
| An audio compressor having both a feedback compressor and a feedforward compressor. The feedback compressor operates so as to provide envelope detection. A sidechain processor which receives an input from the feedback path includes a non-linear low-pass filter and a non-linear amplifier. |
| 5282252 |
Audio equalizer providing reciprocal equalization plus infinite-depth notch |
January 25, 1994 |
| Audio equalizer circuit for adjusting the amount of boost and cut. The circuit uses a combination negative feedback, positive feedback, negative feed-forward and positive feed-forward resulting in boost and cut characteristics which are entirely reciprocal and which, nonetheless prov |
| 5168526 |
Distortion-cancellation circuit for audio peak limiting |
December 1, 1992 |
| Apparatus for reducing distortion in a peak limited audio siganl. The amount of low-frequency spectral energy in the input audio signal is determined for a peak limited signal and used to control low-frequencies in the output audio signal. Identical low-pass filters with cut-off freq |
| 5050217 |
Dynamic noise reduction and spectral restoration system |
September 17, 1991 |
| An audio processor consisting of a "single-ended" dynamic noise reduction system cascaded and cross-coupled with a program-adaptive dynamic equalizer. The audio at the output has a consistent subjective spectral texture even if the spectral texture of the input audio varies widely. F |
| 4888789 |
Adjustable equalizer for compensating for high frequency rolloff and typical AM receivers |
December 19, 1989 |
| An audio equalization circuit for use in an AM transmission system is described which is particularly useful for compensating for the high frequency rolloff found in currently manufactured AM receivers. A single potentiometer adjustment in the feedback path of the equalization circuit |
| 4837824 |
Stereophonic image widening circuit |
June 6, 1989 |
| A circuit for providing enhanced stereophonic sound by processing the L-R signal. A compressor which receives the L+R signal provides a gain control signal. This signal controls the level of the L-R signal and the gain in a tracking VCA. The tracking VCA receives the enhanced L-R signal |
| 4674122 |
Encoding for the FMX companding system |
June 16, 1987 |
| Improved FMX Companding apparatus for FM transmitter. A pilot subsystem which is substantially identical to the FMX audio path is used to develop a control signal which provides amplitude control through a VCA in the main FMX audio path. |
| 4525857 |
Crossover network |
June 25, 1985 |
| A peak limiter is described which employs the Hilbert transform. Effectively distinct processing occurs for low frequency and high frequency signals and harmonic distortion results only when the limiter is excited by high frequencies. |
| 4495643 |
Audio peak limiter using Hilbert transforms |
January 22, 1985 |
| A peak limiter is described which employs the Hilbert transform. Effectively distinct processing occurs for low frequency and high frequency signals and harmonic distortion results only when the limiter is excited by high frequencies. |
| 4460871 |
Multiband cross-coupled compressor with overshoot protection circuit |
July 17, 1984 |
| A multiband compressor suitable for compressing the dynamic range of an audio signal in a broadcasting system is disclosed. The frequency band with the highest predictable energy is selected as a master band with the energy level in this band used to control the gain in the other (slave) |
| 4412100 |
Multiband signal processor |
October 25, 1983 |
| A multiband analog audio processor is described which provides low peak-to-r.m.s. ratios. A distributed crossover configuration is described which, in the presently preferred embodiment, employs bandpass filters with embedded clippers for high frequency processing. Circuits for impro |
| 4249042 |
Multiband cross-coupled compressor with overshoot protection circuit |
February 3, 1981 |
| A multiband compressor suitable for compressing the dynamic range of an audio signal in a broadcasting system is disclosed. The frequency band with the highest predictable energy is selected as a master band with the energy level in this band used to control the gain in the other (slave) |
| 4241266 |
Peak-limiting apparatus for audio signal |
December 23, 1980 |
| A circuit which provides a control signal to dynamically adjust the level of clipping for an audio signal is described. The criterion for allowable clipping employed by the circuit is whether the clipper induced distortion is noticeable; the clipper induced distortion may be audible, how |
| 4228368 |
Polarity correcting circuit |
October 14, 1980 |
| A circuit for controlling the polarity of an asymmetrical waveform, such as a typical audio waveform, is described. The circuit provides smooth polarity switching with substantially no audible switching sound. The smooth switching results from switching each frequency of the audio signal |
| 4208548 |
Apparatus and method for peak-limiting audio frequency signals |
June 17, 1980 |
| A peak-limiting apparatus and method particularly useful in systems employing high frequency pre-emphasis to compensate for steep high frequency rolloff in a receiver, or the like. The apparatus and method is useful in standard AM broadcasting to maximize loudness without noticeable |
