Active room compensation in loudspeaker system
First Claim
1. A method for compensating for acoustic influence of a listening room on an acoustic output from an audio system including at least a left and a right loudspeaker, the method comprising:
- determining a left frequency response LPL between a signal applied to the left speaker and a resulting power average in a listening position,determining a right frequency response LPR between a signal applied to the right speaker and a resulting power average in the listening position,designing a left compensation filter FL,designing a right compensation filter FR,during playback, applying the left compensation filter to a left input signal, and applying the right compensation filter to a right input signal,providing a simulated target function HT representing a simulated target response in the listening position,designing the left compensation filter FL to have a left filter transfer function based on the simulated target function HT multiplied by an inverse of the left frequency response, anddesigning the right compensation filter FR to have a right filter transfer function based on the simulated target function HT multiplied by an inverse of the right frequency response,wherein the simulated target function is obtained by simulating the power emitted by a point source in a corner defined by three orthogonal walls into a one eighth sphere limited by the three walls, and defining the simulated target function as the transfer function between the point source and the emitted power,wherein the simulated emitted power is a power average based on simulations in a plurality of points distributed on the one eighth sphere.
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Accused Products
Abstract
A method for compensating for acoustic influence of a listening room on an acoustic output from an audio system including at least a left and a right loudspeaker, the method comprising determining a left frequency response and a right frequency response, designing a left compensation filter FL, and a right compensation filter FR, and during playback applying the left and right filters to left and right channel inputs. According to the invention, a target response in the listening position is simulated, and the left and right compensation filters are designed to filter transfer functions based on the simulated target function multiplied by an inverse of the left/right frequency responses. By relying on a simulated target instead of relying on an empirical approach, the general impact of a room can be more accurately captured by the target functions.
25 Citations
33 Claims
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1. A method for compensating for acoustic influence of a listening room on an acoustic output from an audio system including at least a left and a right loudspeaker, the method comprising:
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determining a left frequency response LPL between a signal applied to the left speaker and a resulting power average in a listening position, determining a right frequency response LPR between a signal applied to the right speaker and a resulting power average in the listening position, designing a left compensation filter FL, designing a right compensation filter FR, during playback, applying the left compensation filter to a left input signal, and applying the right compensation filter to a right input signal, providing a simulated target function HT representing a simulated target response in the listening position, designing the left compensation filter FL to have a left filter transfer function based on the simulated target function HT multiplied by an inverse of the left frequency response, and designing the right compensation filter FR to have a right filter transfer function based on the simulated target function HT multiplied by an inverse of the right frequency response, wherein the simulated target function is obtained by simulating the power emitted by a point source in a corner defined by three orthogonal walls into a one eighth sphere limited by the three walls, and defining the simulated target function as the transfer function between the point source and the emitted power, wherein the simulated emitted power is a power average based on simulations in a plurality of points distributed on the one eighth sphere. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14)
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15. A method for compensating for acoustic influence of a listening room on an acoustic output from an audio system including at least a left and a right loudspeaker, the method comprising:
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determining a left frequency response LPL between a signal applied to the left speaker and a resulting power average in a listening position, determining a right frequency response LPR between a signal applied to the right speaker and a resulting power average in the listening position, designing a left compensation filter FL, designing a right compensation filter FR, during playback, applying the left compensation filter to a left input signal, and applying the right compensation filter to a right input signal, providing a simulated target function HT representing a simulated target response in the listening position, designing the left compensation filter FL to have a left filter transfer function based on the simulated target function HT multiplied by an inverse of the left frequency response, and designing the right compensation filter FR to have a right filter transfer function based on the simulated target function HT multiplied by an inverse of the right frequency response, the method further comprising; determining a left roll-off frequency at which the left target function exceeds the left frequency response by a given threshold, determining a right roll-off frequency at which the left target function exceeds the right frequency response by a given threshold, calculating an average roll-off frequency based on the left and right roll-off frequencies, estimating a roll-off function as a high pass filter with a cut-off frequency based on the average roll-off frequency, and dividing the left and right frequency responses with the roll-off function before designing the left and right compensation filters. - View Dependent Claims (16, 17, 18, 19, 20, 21, 22, 23, 24)
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25. A method for compensating for acoustic influence of a listening room on an acoustic output from an audio system including at least a left and a right loudspeaker, the method comprising:
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determining a left frequency response LPL between a signal applied to the left speaker and a resulting power average in a listening position, determining a right frequency response LPR between a signal applied to the right speaker and a resulting power average in the listening position, designing a left compensation filter FL, designing a right compensation filter FR, during playback, applying the left compensation filter to a left input signal, and applying the right compensation filter to a right input signal, providing a simulated target function HT representing a simulated target response in the listening position, designing the left compensation filter FL to have a left filter transfer function based on the simulated target function HT multiplied by an inverse of the left frequency response, and designing the right compensation filter FR to have a right filter transfer function based on the simulated target function HT multiplied by an inverse of the right frequency response, the method further comprising; determining a filtered mono frequency response LPM according to LPL FL+LPR FR, determining a filtered side frequency response LPs according to LPL FL−
LPR FR,wherein LPL is the left frequency response, LPL is the right frequency response, FL is the left filter and FR is the right filter, determining a mono target function based on the simulated target function HT, determining a side target function based on the simulated target function HT, designing a mono compensation filter FM having a mono filter transfer function based on the mono target function multiplied by an inverse of the mono response, designing a side compensation filter Fs having a side filter transfer function based on the side target function multiplied by an inverse of the side response, and during playback, applying the mono compensation filter to a mono signal based on the left and right signal inputs, and applying the side compensation filter to a side signal based on the left and right input signals. - View Dependent Claims (26, 27, 28, 29)
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30. A method for compensating for acoustic influence of a listening room on an acoustic output from an audio system including at least a left and a right loudspeaker, the method comprising:
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determining a left frequency response LPL between a signal applied to the left speaker and a resulting power average in a listening position, determining a right frequency response LPR between a signal applied to the right speaker and a resulting power average in the listening position, designing a left compensation filter FL, designing a right compensation filter FR, during playback, applying the left compensation filter to a left input signal, and applying the right compensation filter to a right input signal, providing a simulated target function HT representing a simulated target response in the listening position, designing the left compensation filter FL to have a left filter transfer function based on the simulated target function HT multiplied by an inverse of the left frequency response, designing the right compensation filter FR to have a right filter transfer function based on the simulated target function HT multiplied by an inverse of the right frequency response, and smoothing at least one response using a method comprising; determining a number of peaks per octave in the response, for a portion of the response where the number of peaks per octave is below a first threshold, smoothing the response with a first smoothing width, for a portion of the response where the number of peaks per octave is above a second threshold, smoothing the response with a second smoothing width, wherein said second threshold is greater than said first threshold and said second smoothing width is wider than said first smoothing width, and for a portion of the response where the number of peaks per octave is between the first and second thresholds, smoothing with an intermediate smoothing width.
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31. An audio system including:
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at least a left and a right loudspeaker arranged in a listening room; at least one microphone arranged in a listening position; a signal processing system for compensating for acoustic influence of the listening room on an acoustic output from the loudspeakers, said signal processing system being configured to; apply a test signal to the left speaker, determine a power average based on a signal measured in the microphone, and determine a left frequency response LPL between the test signal and the power average, apply a test signal to the right speaker, determine a power average based on a signal measured in the microphone, and determine a right frequency response LPL between the test signal and the power average, design a left compensation filter FL, and design a right compensation filter FR; and a filtering system configured to; during playback, apply the left compensation filter to a left channel input, and applying the right compensation filter to a right channel input, wherein the signal processing system is provided with a simulated target function HT representing a simulated target response in the listening position, and in that the signal processing system is configured to design the left compensation filter FL to have a left filter transfer function based on the simulated target function HT multiplied by an inverse of the left frequency response, and design the right compensation filter FR to have a right filter transfer function based on the simulated target function HT multiplied by an inverse of the right frequency response, wherein the simulated target function is obtained by simulating the power emitted by a point source in a corner defined by three orthogonal walls into a one eighth sphere limited by the three walls, and defining the simulated target function as the transfer function between the point source and the emitted power, wherein the simulated emitted power is a power average based on simulations in a plurality of points distributed on the one eighth sphere. - View Dependent Claims (32, 33)
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Specification