Abstract: A device for audio mixing includes a cascade input port and a first cascade input component that includes a first cascade input level detector component that detects an audio level of an upstream sum audio signal. The first cascade input port also includes an attenuator component that attenuates the first upstream mix audio signal by a gain corresponding to difference between the upstream sum audio signal value and a detected audio level of an input sum audio signal. The device also includes a summer component where the signals summed include at least the first upstream sum audio signal. The device also includes an input sum level detector component that detects the audio level of the input sum audio signal. The device also includes a mixer component that is configured to provide a mix output signal by summing, where the signals summed include at least the first attenuated upstream mix signal.

Abstract: A system and method for analyzing a signal to monitor the dynamics of its magnitude and frequency characteristics over time. An electronic circuit for identifying feedback in an audio signal, formed in accordance with embodiments of the invention may comprise a feedback control block operable to determine a candidate frequency having potential feedback such that the feedback control block is further operable to perform an iterative analysis of the magnitude of the audio signal at the candidate frequency to determine the growth characteristics of the signal. The electronic circuit may further include a test filter block operable to deploy a test filter at a candidate frequency and a permanent filter block operable to deploy a permanent filter at the candidate frequency if the feedback control block determines that the growth characteristics of the signal at the candidate frequency comprises feedback characteristics after the test filter has been deployed.

Abstract: A system and method for analyzing a signal to identify one or more candidate frequencies that may have a potential feedback problem. An electronic circuit for identifying feedback in an audio signal, formed in accordance with embodiments of the invention, may comprise a feedback control block operable to: 1) determine a magnitude of a first dominant spectral component in a wide-band span of frequencies of a signal, 2) determine a magnitude of a second dominant spectral component in a mid-band span of frequencies of the signal, and 3) determine a magnitude of a third dominant spectral component in a narrow-band span of frequencies of the signal. The feedback control block may then further analyze the magnitude and frequency of the first, second, and third dominant spectral components to determine the presence of feedback characteristics in the signal.

Abstract: A device for audio mixing includes a cascade input port and a first cascade input component that includes a first cascade input level detector component that detects an audio level of an upstream sum audio signal. The first cascade input port also includes an attenuator component that attenuates the first upstream mix audio signal by a gain corresponding to difference between the upstream sum audio signal value and a detected audio level of an input sum audio signal. The device also includes a summer component where the signals summed include at least the first upstream sum audio signal. The device also includes an input sum level detector component that detects the audio level of the input sum audio signal. The device also includes a mixer component that is configured to provide a mix output signal by summing, where the signals summed include at least the first attenuated upstream mix signal.

Abstract: An apparatus having a microphone and a mute circuit (not shown in detail here) operable to be actuated by a rotating door assembly. The apparatus provides a mute circuit suitable to mute the audio microphone when the rotating door assembly is in a closed position and unmute the audio microphone when the rotating door assembly is not in the closed position. Additionally, the mute circuit is impervious to generating audible disturbances in the microphone signal when the rotating assembly door is rotated between open and closed positions. This advantageously allows for the microphone to essentially transition to off when the rotating door assembly is closed and transition to on when the rotating door assembly is open and do so without additional audio disturbance.

Abstract: A method for realizing a digital filter in an electronic system. The method includes first determining the specific number of coefficients to be calculated for a design filter and calculating the value of some of the coefficients for the design filter, typically all but one. Next, a reference filter is selected having the same number of coefficients as the design filter and each coefficient of the reference filter is calculated. With the reference filter's coefficients, the method concludes by determining the value of the remaining coefficients of the design filter that were previously not calculated. The determination is based upon an arithmetic comparison to the coefficients of the reference filter. The system and method improve second-order filter response for certain filters implemented with a direct-form topology.

Abstract: A remote audio device network (RADN) provides a high-value solution for connecting remote audio input and output devices to audio processing equipment in a control/rack room. Costs are kept low through the use of Category 5 (CAT 5) unshielded twisted pair (UTP) cabling and standard technologies for digital audio, control data, and power transmission. Digital audio transmission breaks ground-loops and is highly resistant to EMI. Troubleshooting is simplified using built-in test methods for verifying the power, control, and audio signals. Efficiency of audio bandwidth is maintained for one and two channel input and output devices by using the AES3 (AES/EBU) encoding standard for digital audio which is designed for two-channel audio interconnect. Point-to-point wiring ensures that the DSP equipment is always aware of the location of a connected device such that control data signals allow the DSP equipment to configure and control the connected remote audio devices.

Abstract: An apparatus having a microphone and a mute circuit (not shown in detail here) operable to be actuated by a rotating door assembly. The apparatus provides a mute circuit suitable to mute the audio microphone when the rotating door assembly is in a closed position and unmute the audio microphone when the rotating door assembly is not in the closed position. Additionally, the mute circuit is impervious to generating audible disturbances in the microphone signal when the rotating assembly door is rotated between open and closed positions. This advantageously allows for the microphone to essentially transition to off when the rotating door assembly is closed and transition to on when the rotating door assembly is open and do so without additional audio disturbance.

Abstract: A method for use with equipment having filters, the method characterized by multiplying a matrix having a specified cut-boost setting of a filter of a graphic equalizer by a correction matrix to create a matrix having a corrected cut-boost setting of the filter of the graphic equalizer; adjusting an actual cut-boost setting of the filter of the graphic equalizer to be substantially equal to the corrected cut-boost setting of the filter of the graphic equalizer; and configuring the filter to have a Q value substantially equal to a linearizing Q value. In addition to the foregoing, other method embodiments are described in the claims, drawings, and text forming a part of the present application.

Abstract: An audio tone-control circuit includes 4th-order low-pass, 4th-order band-pass, and 4th-order high-pass filter circuits. The 4th-order low-pass filter circuit has a first phase response and receives and filters an audio signal and generates a first output signal therefrom. The 4th-order band-pass filter circuit has a second phase response that is substantially equal to the first phase response and receives and filters the audio signal to generate a second output signal. The 4th-order high-pass filter circuit has a third phase response substantially equal to the first and second phase responses and receives and filters the audio signal to generate a third output signal. The audio-signal circuit also includes a combining circuit that combines the first, second and third output signals into a combined signal. Furthermore, the filter circuits may be 2nd-order filter circuits instead of 4th-order filter circuits.

Abstract: An echo cancellation invention which does away with the need for an accurate double-talk detector, while maintaining a higher adaptation gain for quicker convergence and also providing increased stability. It does this by operating two filter models of the acoustic path in parallel. One model is adapted continuously to find the most accurate model of the echo path, while the other is not. The echo canceller output is taken from the filter that is not adapted. A comparison of the residual error (echo) is done between the model being adapted and the model being listened to at regular intervals. When the model being adapted has less error (echo) than the model being listened to its filter coefficients are copied to the other model. If the model being adapted has greater error (echo) than the other model (caused by noise diverging the adaptation process) then the adapted model has its coefficients overwritten by the filter that is listened to.

Abstract: A method for use with equipment having filters, the method characterized by multiplying a matrix having a specified cut-boost setting of a filter of a graphic equalizer by a correction matrix to create a matrix having a corrected cut-boost setting of the filter of the graphic equalizer; adjusting an actual cut-boost setting of the filter of the graphic equalizer to be substantially equal to the corrected cut-boost setting of the filter of the graphic equalizer; and configuring the filter to have a Q value substantially equal to a linearizing Q value. In addition to the foregoing, other method embodiments are described in the claims, drawings, and text forming a part of the present application.

Abstract: A multiport bridge controlled by the intelligence of a programmed microcontroller selectively channels audio from a plurality of input ports to a plurality of output ports including a room program output. Coupled to one of the bridge input ports is at least one gated microphone mixer, including multiple microphone channels and an acoustical echo canceller. Expandability is provided by a second, third or up to n microphone mixers each having a separate echo canceller for the associated group of microphone inputs.

Abstract: An ambiance channel produces an ambiance audio signal as a reference threshold such as from a noise microphone located away from the program microphones. Variable gain amplifiers in a plurality of program channels selectively gate open those program channels that have audio present exceeding the ambiance threshold. When the program channels are below the noise threshold and hence inactive, they are gated off and the background noise in the ambiance channel is shunted around the program channel to the output. A control function circuit adjusts the gain of each of the program channels that have been opened as an inverse function of the number of open mics (called NOM). In another disclosed embodiment, a programmed microcomputer receives as inputs the status signals that represent the gated open or gated off conditions of the program channels.

Abstract: A tone control shelving equalizer providing low shelf (bass) boost and cut, and high shelf (treble) boost and cut is disclosed wherein the active filter stages provide sharpened (accelerated) amplitude versus frequency response characteristics at the band transitions to leave the center frequencies uncorrupted by out-of-band effects of the tone controls while maintaining circuit stability and avoiding dropouts due to excessive filter phase shifts. Each high and low end band filter network has multiple poles and offset zeros located at a frequency offset so as to restrict the maximum phase shift of the filter to within a safe level not greater than about 90.degree..

Abstract: An equalizer circuit is disclosed having adjustable bandpass filters connected with operational amplifiers in feedforward and feedback paths so as to form frequency selective boost and cut signal components, which are then combined to form the equalized output signal by a subtractive operation with a direct unfiltered signal path arranged in parallel with the filtered feedforward and feedback paths. The circuit exhibits a constant-Q operation in that it can be adjusted for selected frequency boost and cut without distortion of the component bandwidths of the individual filters.

Abstract: In pulse width modulation (PWM) power regulation and amplification circuits, separate DC rectification and filtering circuitry is eliminated by providing synchronous output switching directly from an available AC source. Output switch steering logic connected to an AC power source, such as a square wave AC signal available at the secondary of an isolation transformer, receives the PWM control signal that is developed by a conventional pulse width modulator in response to an input signal and causes an output switch stage to selectively and synchronously connect the alternating current power across the load with the proper timing and polarity. Preferably the output switching stage includes a low pass filter for filtering out the higher frequency switching transients.