CN115842982A - On-chip loudspeaker impedance curve compensation method - Google Patents

Abstract

The invention aims to provide a loudspeaker impedance curve compensation method, which realizes loudspeaker curve compensation by using an on-chip data converter and a DSP (digital signal processor), and realizes high-fidelity sound reduction miniaturization and low cost. The basic idea of the invention is as follows: the DSP compares the audio signal with the reference signal to generate an amplitude error signal and a phase error signal, the DSP adjusts an amplitude frequency curve and a phase frequency curve of the digital audio signal according to the error signal, the amplitude and the phase of the sound signal output by the loudspeaker are adjusted accordingly, and the amplitude error signal and the phase error signal in the DSP module gradually approach zero to compensate the impedance curve of the loudspeaker through a closed feedback loop formed by the acoustoelectric transducer, the data converter and the DSP.

Description

On-chip loudspeaker impedance curve compensation method

Technical Field

The present invention relates to the field of audio signal technology for driving loudspeakers.

Background

A loudspeaker is a transducer device that converts an electrical signal into an acoustic signal. Ideally, the electrical audio signal is converted to an acoustic signal by a loudspeaker without distortion. The actual loudspeaker has distortion and cannot reproduce the original sound realistically. The distortion is of two kinds: frequency distortion and nonlinear distortion. Frequency distortion is divided into frequency amplitude distortion and frequency phase distortion. The distortion of frequency amplitude is caused by strong sound reproduction to signals of certain frequencies and weak sound reproduction to signals of other frequencies, the distortion destroys the proportion of the original high and low sound loudness, and the original sound tone is changed; the frequency phase distortion is caused by different phase shifts when audio signals with different frequencies pass through a loudspeaker, different time sequences when sounds with different frequencies emitted by a sound box reach a listener, and the like, so that the phase (i.e. time) relation among frequency components of sound of a sound source is changed, the waveform of an output sound signal is not the same as that of an original sound, the phase distortion can generate certain influence on the tone color (the phase relation between fundamental waves and harmonic waves) and the sound image positioning (the front-back and left-right sequence of the sound is disordered) of reproduced sound, and the problems of low sound blur, high sound level deterioration and the like are caused. The nonlinear distortion is caused by the fact that the vibration of the loudspeaker vibration system and the fluctuation of the signal are not completely consistent, and a new frequency component is added in the output sound wave.

The frequency distortion arises from the fact that the impedance curve of the loudspeaker is frequency dependent, the inside of the loudspeaker being a coil, the impedance of the loudspeaker, due to the inductive reactance of the coil, presenting a different resistance value with frequency. A typical loudspeaker impedance curve is shown in figure 1. The solid line is the impedance. The magnitude of the impedance is described in ohms and the corresponding values are read on the left side of the graph. The dotted line is the phase. The phase difference is described in degrees and the corresponding value is read on the right side of the graph. The impedance peaks at low frequencies (resonance frequencies) and then increases with frequency, with the impedance also increasing. This will result in an imbalance in the loudspeaker load when electrical signals of different frequencies are reduced to acoustic signals. The phase curve is non-linear and the group delay of the acoustic signals is not uniform.

In order to solve the problem of sound restoration distortion caused by the impedance curve of the loudspeaker, the high-fidelity sound is corrected by using an electronic system, and the high-fidelity sound is large in size and high in cost.

Disclosure of Invention

Consumer electronics are developing in the direction of portability and high fidelity, and the high fidelity driving circuit of the loudspeaker is promoted to develop in the direction of microminiaturization, digitization and integration. The invention aims to provide an on-chip loudspeaker impedance testing and compensating method, which compensates frequency amplitude distortion and frequency phase distortion caused by loudspeaker impedance fluctuation through a negative feedback loop and is an innovative point of the invention. FIG. 2 is a schematic view of the present invention. The 100 negative feedback compensation loop is sounded by a loudspeaker 101, a microphone 102 collects sound signals, and the sound signals are quantized into digital audio signals by a data converter ADC 104 and then transmitted to a digital signal processor DSP 103; the DSP drives the DAC 105 and thus the speaker, forming a closed loop. The closed feedback loop circuit compares the audio signal with the reference signal by the DSP to generate an amplitude error signal and a phase error signal, the DSP adjusts an amplitude frequency curve and a phase frequency curve of the digital audio signal according to the error signal, the amplitude and the phase of the sound signal output by the loudspeaker are adjusted accordingly, the amplitude error signal and the phase error signal in the DSP module gradually approach zero through a negative feedback loop, the impedance curve of the loudspeaker is compensated, and the DSP compensation parameter is latched.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required to be used in the description of the embodiments are briefly introduced below, and it is obvious that the drawings in the description below are only some embodiments of the present invention, and it is obvious for those skilled in the art that other drawings can be obtained according to the drawings without creative efforts.

FIG. 1 is a schematic diagram of the background art of the present invention.

FIG. 2 is a schematic view of the structure of the present invention.

Detailed Description

Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to the same or similar elements or elements having the same or similar function throughout. The embodiments described below with reference to the accompanying drawings are exemplary only for explaining the present invention and are not construed as limiting the present invention.

As used herein, the singular forms "a", "an", "the" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises" and/or "comprising," when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. It will be understood that when an element is referred to as being "connected" or "coupled" to another element, it can be directly connected or coupled to the other element or intervening elements may also be present. Further, "connected" or "coupled" as used herein may include wirelessly connected or coupled. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.

It will be understood by those skilled in the art that, unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the prior art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.

For the convenience of understanding the embodiments of the present invention, the following description will be further explained by taking several specific embodiments as examples in conjunction with the drawings, and the embodiments are not to be construed as limiting the embodiments of the present invention.

The embodiment of the invention provides an on-chip loudspeaker impedance curve compensation method, a structure schematic and signal processing flow are shown in figure 2, and the method comprises the following processing steps:

the loudspeaker impedance curve compensation loop 100 is divided into an off-chip part (101, 102) and an on-chip part (103, 104, 105), comprising: speaker 101, microphone 102, ADC 104, DSP 103, and DAC 105. The input of the loudspeaker 101 is connected with the output of the DAC, and sound is output through electro-acoustic conversion; the input end of the microphone 102 collects the sound output by the loudspeaker, and the sound-electricity conversion outputs audio telecommunication; the ADC 104 collects the audio electrical signal output by the microphone 102, and quantizes and outputs a digital audio signal; the DSP 103 receives the digital audio signal output from the ADC, compares the audio signal with a reference signal to generate an amplitude error signal and a phase error signal, and adjusts an amplitude frequency curve and a phase frequency curve of the digital audio signal according to the error signal.

The compensation process is divided into two stages. In the first stage, the DSP audio reference signals are a group of signals with constant amplitude and frequency distributed in 20-20 KHz, the group of audio reference signals with constant amplitude drive the loudspeaker to sound after DAC digital-to-analog conversion, and because the impedance of the loudspeaker changes along with the frequency, the amplitude of sound output by the loudspeaker changes along with the frequency, so that amplitude distortion is generated. The distorted sound is collected by a microphone, converted by the ADC and sent back to the DSP. And the DSP compares the audio reference signal with the audio signal fed back to generate an amplitude error signal. According to the amplitude error values of different frequencies, the DSP adjusts a gain frequency curve to compensate the amplitude distortion generated by the loudspeaker. After multiple feedback corrections of the loop, the amplitude error value approaches zero. In the second stage, the DSP audio reference signal is a synchronously transmitted 20-20 KHz signal, and because the impedance of the loudspeaker has sensitivity, the phase of the sound output by the loudspeaker can change along with the frequency, the group delay time is inconsistent, and phase distortion is generated. After the audio reference signal is fed back to the DSP through the microphone and the ADC, the DSP compares the audio reference signal with the group delay time of the feedback signal to generate a phase error signal. The delay time of different frequency signals passing through the loop is compensated, and the phase error value approaches zero after multiple feedback corrections of the loop.

After the compensation process is finished, the amplitude frequency compensation parameter and the phase frequency compensation parameter calculated by the DSP are latched. When the actual loudspeaker plays sound, the input audio signal is corrected by the DSP compensation parameter to offset the fluctuation of the loudspeaker impedance curve and restore high-fidelity sound.

Claims (5)

1. A method for compensating an impedance curve of an on-chip speaker, comprising:

the loudspeaker electroacoustic transducer, the microphone electroacoustic transducer, the data converter and the DSP form a closed negative feedback compensation loop.

2. The method of claim 1, wherein the speaker electroacoustic transducer comprises:

electric (i.e., moving coil), electrostatic (i.e., capacitive), electromagnetic (i.e., reed), piezoelectric (i.e., crystal), and the like.

3. The microphone acoustoelectric transducer of claim 2, comprising:

moving coil, condenser, electret, and silicon micro-microphones.

4. The apparatus of claim 2, wherein the data converter comprises:

analog-to-digital converter ADC, digital-to-analog converter DAC.

5. The method of claim 2, further comprising:

the DSP compares the audio signal with the reference signal to generate an amplitude error signal and a phase error signal, the DSP adjusts an amplitude frequency curve and a phase frequency curve of the digital audio signal according to the error signal, the amplitude and the phase of the sound signal output by the loudspeaker are adjusted accordingly, a closed feedback loop is formed by the sound-electricity/electricity-electricity transducer, the data converter and the DSP, the amplitude error signal and the phase error signal in the DSP module gradually approach zero, and the impedance curve of the loudspeaker is compensated.

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