Patent Translate Powered by EPO and Google Notice This translation is machine-generated. It cannot be guaranteed that it is intelligible, accurate, complete, reliable or fit for specific purposes. Critical decisions, such as commercially relevant or financial decisions, should not be based on machine-translation output. DESCRIPTION JP2010258880 An object of the present invention is to improve the sound quality at low cost by improving transient characteristics immediately before an on-vehicle speaker with a small amount of calculation, and as a result, improve the feeling of sound field. A digital waveform compensation circuit (12) delays an input signal by a delay time until a distortion component of a first wave at the time of impulse input obtained by an impulse response measurement result of a vehiclemounted speaker (15). 121, and a low pass filter (LPF 122) that generates a waveform having a width corresponding to the distortion waveform of the first wave of the delayer output based on the filter characteristics obtained by the impulse response measurement result, and the output of the low pass filter The phase inversion circuit 123 generates an opposite phase signal component that reduces the distortion component of the first wave, and the adder 125 adds the input signal and the output of the phase inversion circuit. [Selected figure] Figure 2 Digital waveform compensation circuit [0001] The present invention relates to a digital waveform compensation circuit suitable for use in an amplifier to which an on-vehicle speaker is connected. [0002] In-vehicle speakers used in the vehicle interior acoustic space have distortion response waveforms that are less responsive than an ideal sound waveform due to insufficient strength of vehicle structures such as iron plates and interior materials used as enclosures around the 08-05-2019 1 speakers It is known that many components (undershoot and overshoot) occur. This distortion component waveform is an unnecessary component not included in the original waveform, and is one of the causes that adversely affect the sound quality. [0003] For this reason, although improvement tendency is seen by securing the strength of the vehicle structure etc., complete measures are difficult, and cost for that purpose was required. In addition, in order to secure the strength, the weight increase is caused, the adverse effect on the fuel efficiency is considered, and sufficient measures can not be taken. Therefore, measures have conventionally been taken on the amplifier side to which the in-vehicle speaker is connected. For example, distortion component waveform reduction processing is performed by convolution operation of an impulse response using an adaptive filter (FIR: Finite Impulse Response) It had been. [0004] On the other hand, conventionally, with regard to the non-uniformity of the frequency characteristic at the viewing point due to the interference between the direct sound from the speaker and the reflected sound from the wall etc., the frequency of the reflected sound intervened between the delay means and the level adjustment means A sound field correction device has been proposed that compensates with a low pass filter (LPF) whose filter characteristics are determined based on the characteristics (see, for example, Patent Document 1). [0005] Japanese Patent Application Laid-Open No. 60-193776 [0006] However, according to the reduction processing of the distortion component waveform by the convolution operation using the above-mentioned adaptive filter, a huge amount of operation is required, resulting in an increase in cost. 08-05-2019 2 Further, the technology disclosed in Patent Document 1 relates to sound field correction for interference between direct sound and reflected sound, and is not sound field correction for direct sound on the front surface of a speaker. [0007] The present invention has been made to solve the above-mentioned problems, and the transient characteristics immediately before a vehicle-mounted speaker are improved with a small amount of calculation to improve the sound quality at a low cost, and as a result, the feeling of sound field is improved. It is an object of the present invention to provide a digital waveform compensation circuit that can [0008] In order to solve the above-mentioned problems, the digital waveform compensation circuit of the present invention has an input signal corresponding to the delay time until the distortion component of the first wave at the time of impulse input obtained by the impulse response measurement result of the on-vehicle speaker A low-pass filter for generating a waveform having a width corresponding to the distortion waveform of the first wave of the delayer output based on the delay characteristic delayed by just a second delay, the filter characteristic obtained by the impulse response measurement result, A phase inverting circuit that generates an antiphase signal component that reduces the distortion component of the first wave from the output of a band pass filter, and an adder that adds the input signal and the output of the phase inverting circuit It is. [0009] According to the digital waveform compensation circuit of the present invention, it is possible to improve the sound quality at low cost by improving the transient characteristics immediately before the on-vehicle speaker with a small amount of calculation, and as a result, it is possible to improve the feeling of sound field. [0010] It is a figure which shows the structural example of the vehicle-mounted acoustic equipment in which the digital waveform compensation circuit which concerns on Embodiment 1 of this invention is used. 08-05-2019 3 It is the figure which showed the internal structure of the digital waveform compensation circuit which concerns on Embodiment 1 of this invention with an equivalent circuit. FIG. 5 is a diagram schematically showing the operation of the digital waveform compensation circuit according to the first embodiment of the present invention. It is the figure which showed the internal structure of the digital waveform compensation circuit which concerns on Embodiment 2 of this invention with an equivalent circuit. It is the figure which showed the internal structure of the digital waveform compensation circuit which concerns on Embodiment 3 of this invention with an equivalent circuit. It is the figure which showed the frequency characteristic by the digital waveform compensation circuit based on Embodiment 1 of this invention in comparison with a prior art example. [0011] Hereinafter, a digital waveform compensation circuit according to an embodiment of the present invention will be described in detail with reference to the drawings. Embodiment 1 FIG. 1 is a diagram showing a configuration example of an on-vehicle acoustic device in which a digital waveform compensation circuit according to a first embodiment of the present invention is used. [0012] As shown in FIG. 1, the in-vehicle audio device 1 includes an ADC (Analog Digital Converter) 11, a digital waveform compensation circuit 12 according to the first embodiment of the present invention, a DAC (Digital Analog Converter) 13, and a power amplifier. 14 and an on-vehicle speaker 15. [0013] The ADC 11 converts an analog input audio signal into a digital audio signal and outputs the digital audio signal to the digital waveform compensation circuit 12. 08-05-2019 4 As described later, the digital waveform compensation circuit 12 generates the first sound (overshoot / undershoot) at the time of impulse input obtained from the impulse response measurement result of the in-vehicle speaker 15 in advance of the digital audio signal output from the ADC 11 The delay output is delayed by a delay time until a distortion component occurs, and this delay output is also formed into a waveform having a width corresponding to the distortion waveform of the first wave of the delay output based on the filter characteristics obtained by the impulse response measurement result. Further, the signal component of the opposite phase for reducing the distortion component of the first wave is generated, added to the input digital audio signal, and output to the DAC 13. Details will be described later. [0014] The DAC 13 converts the digital audio signal output from the digital waveform compensation circuit 12 into an analog audio signal and outputs the analog audio signal to the power amplifier 14. The power amplifier 14 amplifies the analog audio signal output by the DAC 13 and outputs the amplified signal to the on-vehicle speaker 15 which is an electroacoustic transducer. [0015] Here, each of the ADC 11, the digital waveform compensation circuit 12, and the DAC 13 is implemented by being implemented in the digital signal processing device 10 (DSP) and subjected to signal processing in the DSP 10. Details will be described later. [0016] FIG. 2 is a diagram showing an internal configuration of the digital waveform compensation circuit 12 according to the first embodiment of the present invention as an equivalent circuit. The digital waveform compensation circuit 12 is composed of an IIR (Infinite Impulse Response) filter having an impulse response function that returns a nonzero value at infinite time, and a delay unit (Delay) 121 and a low pass filter 122 (hereinafter referred to as LPF 122). , A phase inverting circuit 123, a level adjusting circuit 124, and an adder 125. [0017] 08-05-2019 5 The delay unit 121, delay time until the distortion waveform component of the first wave related to the overshoot and undershoot at the time of impulse input obtained by the impulse signal measurement result of the in-vehicle speaker 15 and the input signal (INPUT) The signal is delayed by (td) and output to the LPF 122. [0018] The LPF 122 generates a waveform having a width corresponding to the distortion waveform of the first wave at the output of the delay device 121 based on the filter characteristic obtained by the impulse response measurement result in advance, and outputs the waveform to the phase inversion circuit 123. The phase inversion circuit 123 generates, from the output of the LPF 122, a signal component of the opposite phase for reducing the distortion component of the first wave, and outputs the signal component to the adder 125. [0019] The adder 125 adds the signal obtained by adjusting the level of the input signal (INPUT) by the level adjustment circuit 124 and the output of the phase inversion circuit 123 described above, and outputs the result as an OUTPUT signal to the power amplifier 14. [0020] FIG. 3 is a diagram schematically showing the operation of the digital waveform compensation circuit 12 according to the first embodiment of the present invention. The operation of the digital waveform compensation circuit 12 according to the first embodiment of the present invention shown in FIG. 1 and FIG. 2 will be described below with reference to FIG. [0021] 08-05-2019 6 As described above, in the on-vehicle speaker 15, distortion waveforms of overshoot and undershoot with poor transient response occur with respect to the input sound signal. Here, waveform compensation in the digital domain is performed in order to cancel out this distortion waveform component. Therefore, the in-vehicle speaker 15 is installed in the vehicle compartment in advance, the impulse response waveform on the front surface of the in-vehicle speaker 15 is measured (a), and attention is paid to distortion waveform components generated after fundamental wave driving. It is necessary to set in advance in DSP 10 (digital waveform compensation circuit 12) parameters including delay time and filter characteristics for simulating the distortion component of the first wave for the shoot. [0022] After the above-described preparation processing, the digital waveform compensation circuit 12 delays the signal branched from the input signal (INPUT) by the time td according to the parameter set by the delay unit 121 and passes it through the LPF 122 and the LPF 122 A waveform corresponding to the width of the distortion waveform component is generated and output to the phase inversion circuit 123. [0023] The phase inversion circuit 123 generates a signal (distortion compensated waveform) having an opposite phase to the distortion waveform of the first wave by the output of the LPF 122 (b), and the adder 125 adjusts the input signal (INPUT) by the level adjustment circuit 124. Is added to the level-converted signal to cancel the distorted waveform (c), and the distortion component is reduced by outputting to the power amplifier 14. [0024] Here, td is the delay time until the distortion component of the first wave is generated at the time of impulse input which is obtained by the impulse response measurement result of the in-vehicle speaker 15 performed in advance, and the filter characteristic is also the same in advance. This refers to a parameter for generating a waveform having a width corresponding to the distortion waveform of the first wave obtained by the impulse response measurement result of the onvehicle speaker 15 performed. [0025] According to the digital waveform compensation circuit according to the first embodiment of the present invention described above, only the delay time up to the occurrence of the distortion 08-05-2019 7 component of the first wave at the time of impulse input obtained by the impulse response measurement result of the on-vehicle speaker 15 The delayed output is used to generate a distortion waveform component having a width corresponding to the distortion waveform based on the filter characteristic similarly obtained by the impulse response measurement result, and generates an antiphase signal component that reduces the distortion component of the first wave. Digital waveform compensation is realized by adding and outputting the input digital audio signal, and the sound quality can be improved. Further, by configuring the above-described digital waveform compensation circuit 12 with an IIR filter and processing the signal by the DSP 10, the amount of calculation is small, and the sound quality is improved inexpensively, and as a result, the sound field feeling of the on-vehicle speaker 15 is obtained. It can be improved. [0026] Second Embodiment FIG. 4 is a diagram showing an internal configuration of a digital waveform compensation circuit according to a second embodiment of the present invention as an equivalent circuit. [0027] As shown in FIG. 4, in the digital waveform compensation circuit according to the second embodiment of the present invention, the digital waveform compensation circuit 12 according to the first embodiment of the present invention shown in FIG. On the other hand, more effective waveform compensation can be performed by performing a plurality of digital waveform compensations including the second wave. Here, a second-order IIR filter is shown. Therefore, the sound quality is improved, and as a result, the sound field feeling of the in-vehicle speaker 15 can be improved. Further, by processing the respective digital waveform compensation circuits 12 connected in parallel by the DSP 10, the amount of calculation is small, and the sound quality can be improved inexpensively. 08-05-2019 8 [0028] Also in the second embodiment described above, the impulse response waveform on the front surface of the in-vehicle speaker 15 installed in the vehicle compartment is measured in advance as in the first embodiment, and the distortion component is detected in the DSP 10 (digital waveform compensation circuit 12). It is essential to set parameters related to delay time and filter characteristics to simulate. [0029] Third Embodiment FIG. 5 is a diagram showing an internal configuration of a digital waveform compensation circuit according to Embodiment 3 of the present invention as an equivalent circuit. [0030] As shown in FIG. 5, in the digital waveform compensation circuit according to the third embodiment of the present invention, the digital waveform compensation circuit 12 according to the first embodiment of the present invention shown in FIG. In the second embodiment described above, the impulse response is also added / subtracted by connecting the digital waveform compensation circuits 12 in parallel, but as shown in the third embodiment, when the digital waveform compensation circuits 12 are slave-connected, The convolution of each of the cascaded digital waveform compensation circuits 12 makes it possible to perform waveform compensation with higher effect. [0031] Therefore, according to the digital waveform compensation circuit according to the third embodiment, the sound quality can be improved, and as a result, the sound field feeling of the onvehicle speaker 15 can be improved. Further, by performing signal processing of the dependently connected digital waveform compensation circuit 12 with the DSP 10, more effective waveform compensation is performed, the amount of calculation is small, and the sound quality can be improved inexpensively. 08-05-2019 9 [0032] Also in the third embodiment described above, as in the first and second embodiments, the impulse response waveform on the front surface of the in-vehicle speaker 15 installed in the vehicle compartment is measured in advance, and the DSP 10 (digital waveform compensation circuit 12) It is essential to set parameters related to delay time and filter characteristics to simulate distortion components. [0033] FIG. 6 is a diagram showing the frequency characteristics of the digital waveform compensation circuit 12 according to the first embodiment of the present invention described above in comparison with a conventional example. 6 (a) shows a conventional example, and FIG. 6 (b) shows a response waveform of the digital waveform compensation circuit 12 according to the first embodiment of the present invention immediately before the on-vehicle speaker 15 and is shown in FIG. Thus, it can be seen that the overshoot and undershoot first wave distortion components are reduced. Here, a value set as a parameter in the DSP 10 (digital waveform compensation circuit 12) exemplifies a case where the delay time (td) of the delay unit 121 is 0.15 ms and the cutoff frequency (fc) of the LPF 122 is 800 Hz. There is. [0034] As described above, according to the digital waveform compensation circuit according to the first to third embodiments of the present invention, the transient characteristic immediately before the on-vehicle speaker is improved with a small amount of calculation to improve the sound quality inexpensively. As a result, the feeling of the sound field can be improved. [0035] The functions of the digital waveform compensation circuit 12 shown in FIG. 2, FIG. 4 and FIG. 5 may all be realized by software by the DSP 10, or at least a part of them may be realized by hardware. 08-05-2019 10 For example, the digital waveform compensation circuit 12 delays the input signal by a delay time until the distortion component of the first wave at the time of impulse input obtained by the impulse response measurement result of the on-vehicle speaker 15 is generated, thereby measuring impulse response. Based on the filter characteristics obtained as a result, the distortion waveform of the first wave is generated, the signal component of the reverse phase is generated to reduce the distortion component of the first wave, and the data processing of adding to the input signal is one or more. The program may be realized on a computer, and at least a part of the program may be realized in hardware. [0036] Reference Signs List 1 in-vehicle audio device, 10 DSP, 11 ADC, 12 digital waveform compensation circuit, 13 DAC, 14 power amplifier, 15 in-vehicle speaker, 121 delay unit, 122 low pass filter (LPF), 123 phase inverting circuit, 124 level adjustment Circuit, 125 adders. 08-05-2019 11
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