JPS64848B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a loudness control device used in audio equipment such as stereos.

Conventional configuration and its problems The Fletschier-Munson curve represents the human loudness auditory characteristics. This indicates that when the loudness level is high, the difference in the sense of volume depending on frequency is relatively small and flat, but as the loudness level decreases, it becomes difficult to hear bass and treble sounds. There is a loudness control circuit to compensate for this.
FIG. 1 shows a circuit that has been commonly used in the past. Further, the loudness compensation characteristics of this circuit are shown in FIG.

According to this conventional circuit, the loudness compensation characteristic is fixed even though the reproduced sound constantly changes, and there is a problem in that it cannot cope with transient sound level fluctuations. In addition, the loudness compensation characteristic is close to the Fletschier-Munson loudness curve, and does not take into account the relationship between the sound pressure level during recording and the sound pressure level during playback, so the loudness compensation characteristic may be overemphasized and may not be good. There was a problem that loudness compensation was not possible.

OBJECTS OF THE INVENTION An object of the present invention is to provide a loudness control device that can automatically perform loudness control that matches human auditory characteristics.

Structure of the Invention For this reason, the present invention provides an equalizer characteristic between a preamplifier and a main amplifier, based on a sound pressure level with a loudness curve such as Fletcher-Munson, which is the difference between an equal loudness curve at a minimum control level and a reference equal loudness curve. In addition, we inserted an equalizer that took into account the characteristics of the speaker, and installed a filter on the output side of the main amplifier consisting of a parallel circuit consisting of a resistor element whose resistance value changes depending on the magnitude of the current value, and a capacitor. In this way, the reproduction output is equalized by the difference between the equal loudness curve of the reproduction level and the standard loudness curve, and when the input voltage is small, the characteristics of the equalizer can be obtained as is, and when the input voltage becomes large. To provide a loudness control device in which the low frequency range is eventually cut and the amount of boost in the low frequency range is gradually reduced, thereby automatically changing the loudness characteristic to a target characteristic depending on the input voltage.

DESCRIPTION OF EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. 3 to 7. In Fig. 3, 1 is a preamplifier;
2 is an equalizer whose equalizer characteristics are set to be the difference between the minimum control level equal loudness curve and this reference equal loudness curve, with the sound pressure level having a Fletschier-Munson loudness curve as a reference, and also takes speaker characteristics into consideration. ,
The equalizer characteristics here are based on a level of 100 dB, and are the characteristics of the difference between the equal loudness curve at a level 30 dB lower than the standard equal loudness curve. 3 is a main amplifier, 4a is a low frequency network circuit, and 4b is a high frequency network circuit. Reference numeral 5a denotes a variable loudness high-pass filter for low frequencies, and as shown in FIG. 4, it is constituted by a circuit in which a resistive element R whose resistance value changes depending on the current and a capacitor C are connected in parallel. Therefore, when the input voltage is small, the resistance element R
Since the resistance value of is small and the current flows in the direction of resistance element R, it hardly acts as a filter, and the characteristics of equalizer 2 are obtained as is, and as the input voltage increases, the current flowing through resistance element R increases. , since the resistance value increases, current flows through the capacitor C, which acts as a high-pass filter. Therefore, the characteristic is that the low range is cut off from around the cutoff frequency. Reference numeral 5b denotes a variable loudness resonant circuit for high frequencies, and as shown in FIG. 5, it is composed of a circuit in which a resistive element R whose resistance value changes depending on the current, a capacitor C, and a coil L are connected in parallel. The effect of resistance element R is similar. 6a and 6b are speakers for low tone and high temperature, respectively.

Note that examples of the resistance element R whose resistance value changes continuously depending on the current include a positive characteristic thermistor, a thermistor, a varistor, a pilot lamp, and the like.

FIG. 6 shows the characteristics of the high-pass filter 5a. Furthermore, FIG. 7 shows the characteristics of the loudness control device. Due to this characteristic, loudness correction can be automatically performed depending on the level of the signal, and sound with corrected low and high frequencies is reproduced.

Effects of the Invention According to the loudness control device of the present invention, as is clear from the above explanation, the signal is generated by the interaction between the equalizer inserted between the preamplifier and the main amplifier and the loudness variable filter circuit on the output side of the main amplifier. Loudness can be automatically corrected depending on the level, and rich sound with corrected low and high frequencies can be reproduced.

[Brief explanation of the drawing]

1 and 2 show a conventional example, FIG. 1 is a loudness control circuit diagram, FIG. 2 is a characteristic diagram of the same, FIGS. 3 to 7 show an embodiment of the present invention, and FIG. is a configuration diagram of the loudness control device, FIG. 4 is a circuit diagram of a high-pass filter, FIG. 5 is a high-frequency resonance circuit diagram, FIG. 6 is a characteristic diagram of the high-pass filter, and FIG. 7 is a characteristic diagram of the loudness control device. . 1 is a preamplifier, 2 is an equalizer, 3 is a main amplifier, 4a and 4b are network circuits, 5a is a variable loudness high-pass filter, and 5b is a variable loudness resonant circuit.

Claims (1)

[Claims] 1 An equalizer provided between a preamplifier and a main amplifier, and a filter provided on the output side of the main amplifier, and the equalizer has characteristics based on a sound pressure level with a loudness curve such as that of Fletchyer Munson. The filter is configured to be the difference between the minimum control level equal loudness curve and the reference equal loudness curve, and the filter is constructed of a parallel circuit consisting of a resistive element and a capacitor whose resistance value changes depending on the magnitude of the current value. 1. A loudness control device configured to perform loudness correction according to the magnitude of an input signal.