Method for operating a loudspeaker

Abstract

The invention relates to a method for operating a loudspeaker, in particular a moving-coil loudspeaker, in which a reference signal is processed to generate a pilot tone and a useful signal is processed to generate sound by means of the loudspeaker. According to the invention, the reference signal is generated depending on a property of the useful signal. Advantageously, the reference signal is generated depending on an electrical property, preferably a voltage, a current, and / or a power, of the useful signal.

Description

[0001] The invention relates to a method for operating a loudspeaker, in particular a moving-coil loudspeaker, in which a reference signal is processed to generate a pilot tone and a useful signal is processed to generate sound by means of the loudspeaker.

[0002] It is known from practical experience to linearize the drive parameters of dynamic moving-coil loudspeakers by superimposing a reference signal in addition to the desired signal and measuring the current drawn by the loudspeaker's voice coil. The reference signal and the measured current are fed into a mathematical model of the loudspeaker and further processed for loudspeaker operation.

[0003] The invention is based on the objective of improving the reproduction of the useful signal by means of the loudspeaker.

[0004] According to the invention, this problem is solved by generating the reference signal depending on a property of the useful signal.

[0005] If the pilot tone is constructively superimposed on the sound generated by the desired signal, the resulting excursions of the loudspeaker diaphragms, set in motion by the two signals, also add up. This leads to a reduction in the diaphragm excursion available for outputting the desired signal and thus counteracts the goal of expanding the usable diaphragm excursion range through linearization. The inventors recognized that the desired signal itself could take over the function of the reference signal and thus be used as a reference signal.

[0006] By linking the reference signal to a characteristic of the audio signal, it becomes possible to adapt the reference signal to the audio signal. In particular, the reference signal, and thus the pilot tone, can be reduced if the audio signal itself can take over the function of the reference signal. If this occurs, the loudspeaker can be used to a greater extent, or even completely, for reproducing the audio signal. Specifically, the excursion of its diaphragm can be fully utilized for generating the sound to be reproduced by the audio signal and is no longer needed for reproducing the pilot tone. Furthermore, this avoids or even eliminates the possibility of intermodulation effects, which can distort the sound, caused by the pilot tone being superimposed on the audio signal.

[0007] In one embodiment of the invention, the reference signal is generated depending on an electrical property, preferably a voltage, a current, a power and / or a level, of the useful signal.

[0008] In one embodiment of the invention, the reference signal is generated in such a way that a signal quantity, preferably signal amplitude, of the reference signal depends on the useful signal quantity, preferably useful signal amplitude.

[0009] Advantageously, the reference signal is generated with a maximum pilot tone amplitude intended for the loudspeaker if the useful signal amplitude is smaller than a lower useful signal amplitude limit.

[0010] Preferably, the reference signal is generated with a minimum pilot tone amplitude when the useful signal amplitude is greater than an upper limit value. The minimum pilot tone amplitude can be 0.

[0011] In a particularly preferred embodiment of the invention, the reference signal is generated with a variable amplitude that depends on the size of the useful signal amplitude, preferably when the useful signal amplitude is greater than the lower useful signal amplitude limit and the useful signal amplitude is smaller than the upper useful signal amplitude limit.

[0012] Conveniently, the size of the amplitude of the reference signal with variable amplitude is a function of the useful signal amplitude.

[0013] In one embodiment of the invention, a function of the useful signal amplitude includes an evaluation of the emergency signal (e.g. by a low-pass filter), squaring of the useful signal, formation of the expected value of the, preferably squared and / or filtered, useful signal, a comparison of the expected value with threshold values ​​of a switch, a determination of factors from switches with values ​​between [0,1], a smoothing of these values ​​with a long time constant, and / or a multiplication of the smoothed values ​​with the pilot tone.

[0014] Advantageously, the reference signal is chosen such that the pilot tone lies within a frequency spectrum in which it is inaudible to the human ear. Preferably, a sinusoidal signal with a frequency significantly lower than the loudspeaker's resonant frequency is used.

[0015] As mentioned at the outset, the reference signal and the result of the measured current are expediently fed into a mathematical model of the loudspeaker and further processed for the operation of the loudspeaker. In one embodiment of the invention, values ​​deviating from the model's output are compensated for linearization.

[0016] In one embodiment of the invention, the drive parameters for the loudspeaker are linearized, preferably after generation of the reference signal. Advantageously, the method is used to generate operating parameters for the loudspeaker, in particular parameters for driving at least one diaphragm of the loudspeaker, preferably in conjunction with a linearization of the drive parameters.

[0017] The invention further relates to a computer program comprising instructions which, when the program is executed by a computer, cause it to perform the method described above.

[0018] The computer program is expediently stored on a digital signal processor, a data carrier, preferably RAM, ROM, CD or the like, or a device, in particular a personal computer, a device with an embedded processor, preferably a digital signal processor, a computer embedded in a device, a smartphone, a computer program or a sequence of signals suitable for transmission over a computer network, in particular the Internet, representing data.

[0019] The device in question may be an amplifier or a loudspeaker, or the device may include an amplifier or a loudspeaker.

[0020] The invention further relates to a data carrier signal which transmits the aforementioned computer program.

[0021] Furthermore, the invention relates to a digital signal processor on which the computer program is stored, an audio amplifier comprising a digital signal processor on which the computer program is stored, and / or a sound reinforcement unit comprising an audio amplifier comprising a digital signal processor on which the computer program is stored, and a loudspeaker connected to the audio amplifier.

[0022] In a further development of the invention, the invention relates to a motor vehicle, in particular an automobile, which is equipped with a sound system.

[0023] The invention is explained in more detail below with reference to an exemplary embodiment and the accompanying drawings relating to that embodiment. The drawings show: Fig. 1. Schematically, a method according to the state of the art, Fig. 2 schematically a method according to the invention, Fig. 3 a detail of the procedure according to Fig. 2, Fig. 4 Details of the procedure according to Fig. 3 and Fig. 5 examples concerning the implementation of the procedure.

[0024] Fig. Figure 1 shows schematically how a reference signal A0Sin(Φ(n)) is usually used to generate a pilot tone with a useful signal Audio_in x i (n) is added to allow for the adjustment of loudspeaker drive parameters for linearization, independent of the signal. Particularly when playing back a low-frequency signal with a large amplitude, this can lead to audible intermodulation effects and limit the range of excursion of a loudspeaker diaphragm that can be used for reproducing the signal.

[0025] Fig. Figure 2 shows an embodiment of the invention with amplitude-dependent pilot tone usage. The useful signal is audio_in x. i (n) A low-frequency sine wave A0Sin(Φ(n)) with variable amplitude is superimposed as a reference signal. The amplitude depends on the useful signal, in particular on its electrical properties such as voltage, current, or power, and / or their level. It is reduced if the useful signal is so strong that the reference signal is not required, or not fully required, for linearizing loudspeaker drive parameters. Now, the entire range of diaphragm excursion, extended by the linearization, is available for use by the useful signal. The reduction can be further explained below using the Fig. As explained in section 3, the level of the input signal depends on its amplitude and can be calculated as a function of that amplitude. Such a function can, for example, include: a function of the useful signal amplitude; an evaluation of the emergency signal (e.g., by a low-pass filter); squaring the useful signal; calculating the expected value of the, preferably squared and / or filtered, useful signal; comparing the expected value with the threshold values ​​of a switch; determining factors from switches with values ​​between [0,1]; smoothing these values ​​with a long time constant; and / or multiplying the smoothed values ​​by the pilot tone.

[0026] Furthermore, a lower limit for the useful signal amplitude can be provided. If the amplitude of the useful signal is below the limit, the pilot tone is output with a maximum amplitude specified for the pilot tone, which is necessary for adjusting loudspeaker drive parameters for linearization.

[0027] An upper limit for the useful signal amplitude can be provided to create a useful signal amplitude range in which the reference signal is not required and only the useful signal is used and linearized. After linearization, an output signal, Audio_out x, is sent to the loudspeaker. o (n) issued.

[0028] Fig. Figure 3 schematically shows how the signals under “calc gain” are calculated. Fig. 2 can be processed. The useful signal Audio_in x iSignal (n) is filtered using a low-pass filter. The average power or intensity of the filtered signal is determined over time using an RMS level detector, which uses the values ​​(AT) and (RT) as filter factors for the rising and falling edges of the squared signal, respectively. When an RMS threshold is exceeded, a weighting factor of 1 is reduced by a switch. Fig. Figure 4 shows, as examples, a hysteresis switch (a) with two threshold values ​​Th1, Th2. Alternatively, a Harter switch (b) with only one threshold value or a switch with a smoothed transition between TH1, Th2 can be used, shown here as switch (c).

[0029] A smoothing device ("smoother") smooths the signal output by the switch to avoid abrupt transitions. In this example, exponential smoothing is used, and when the signal falls below a threshold of Al(n), the phase of the sine wave generator is additionally set to zero to allow for a smoother fade-in of the sine wave signal with quiet audio signals.

[0030] Fig. 5 shows for switch c) to Fig. 4. For example, under a) an amplitude profile of the useful signal Audio_in x i (n) and, under b), an average power or intensity of the filtered signal. In Fig. 5 c) is represented as a solid line as the output signal size SG before smoothing in the “smoother” and as a dashed line as the smoothed output function A1(n).

[0031] As can be seen in the graphs, after a period of time shortly after 6 seconds (sec), a lower limit Th1 of the power / intensity is reached, and the output maximum signal size SG is reduced to 0 until shortly after 7 seconds (sec) after reaching the upper limit Th2. After the power / intensity has fallen below the upper limit Th2 again, the output signal size SG is gradually increased until it is output at its maximum again when the lower limit Th1 is reached. The graph shows how the smoothed output function A1(n) lags behind the output signal size SG.

Claims

[1] Method for operating a loudspeaker, in particular a moving-coil loudspeaker, in which a reference signal is processed to generate a pilot tone and a useful signal is processed to generate sound by means of the loudspeaker, characterized by , that the reference signal is generated depending on a property of the useful signal. [2] Method for operating a loudspeaker, in particular a moving-coil loudspeaker, in which a reference signal is processed to generate a pilot tone and a useful signal is processed to generate sound by means of the loudspeaker, in which drive parameters, in particular a drive signal, are generated to actuate the loudspeaker, characterized by , that the pilot tone is used for linearization. [3] Method according to claim 1 or 2, characterized by, that the reference signal is generated depending on an electrical property, preferably a voltage, a current, a power and / or a level, of the useful signal. [4] Method according to any one of claims 1 to 3, characterized by that a signal quantity, preferably signal amplitude, of the reference signal depends on the useful signal quantity, preferably useful signal amplitude. [5] Method according to claim 4, characterized by , that the reference signal is generated with a maximum pilot tone amplitude intended for the loudspeaker when the useful signal amplitude is smaller than a lower useful signal amplitude limit. [6] Method according to claim 3 or 4, characterized by , that the reference signal is generated with a minimum pilot tone amplitude if the useful signal amplitude is greater than an upper useful signal amplitude limit. [7] Method according to claim 6, characterized by , that the minimum pilot tone amplitude is = 0. [8] Method according to any one of claims 3 to 7, characterized by , that the reference signal is generated with a variable amplitude that depends on the size of the useful signal amplitude, preferably when the useful signal amplitude is greater than the lower useful signal amplitude limit and the useful signal amplitude is smaller than the upper useful signal amplitude limit. [9] Method according to any one of claims 3 to 8, characterized by , that the size of the amplitude of the reference signal with the variable amplitude is a function of the useful signal amplitude. [10] Method according to any one of claims 1 to 9, characterized by, that a function of the useful signal amplitude includes an evaluation of the useful signal (e.g. by low-pass filter), squaring of the useful signal, formation of the expectation value of the, preferably squared and / or filtered, useful signal, a comparison of the expectation value with threshold values ​​of a switch, a determination of factors from switches with values ​​between [0,1], a smoothing of these values ​​with a long time constant, and / or a multiplication of the smoothed values ​​with the pilot tone and / or comprises. [11] Method according to any one of claims 1 to 10, characterized by , that a method for generating loudspeaker drive parameters, in particular a drive signal with which the loudspeaker is actuated, is used. [12] Method according to claim 11, characterized by that the loudspeaker drive parameters are linearized, preferably after generation of the reference signal. [13] Computer program comprising instructions which, when the program is executed by a computer, cause it to execute the method according to any one of claims 1 to 12. [14] Computer program according to claim 13, characterized by that the computer program is stored on a digital signal processor, a data carrier, preferably RAM, ROM, CD or the like, or a device, in particular a personal computer, a device with an embedded processor, preferably a digital signal processor, a computer embedded in a device, a smartphone, or is a sequence of signals suitable for transmission over a computer network, in particular the Internet, representing data. [15] Computer program according to claim 13 or 14, characterized by that the device is an amplifier or a loudspeaker, or that the device includes an amplifier or a loudspeaker. [16] Data carrier signal which transmits the computer program according to claim 13. [17] Digital signal processor on which the computer program according to claim 13 is stored. [18] Audio amplifier comprising a digital signal processor on which the computer program according to claim 13 is stored. [19] Sound reinforcement unit comprising an audio amplifier, which includes a digital signal processor on which the computer program according to claim 13 is stored, and at least one loudspeaker connected to the audio amplifier. [20] Motor vehicle, in particular automobile, which is equipped with a sound system according to claim 19.

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