JPH04109799A - Acoustic signal reproducing device - Google Patents

Abstract

PURPOSE:To reproduce the frequency characteristic to a state close to a flat characteristic in a listening sense even when a level of an acoustic signal is small by extracting part of a frequency band of the acoustic signal and increasing/decreasing the level of the part of the frequency band corresponding to the extracted level. CONSTITUTION:While an acoustic signal is inputted to a tone control circuit 15b, part of the signal is inputted to a low pass filter 11 and a low frequency component of the acoustic signal is extracted. The extracted low frequency component is converted into a DC voltage by a waveform shaping circuit 12 and inputted to an adder 14 together with an output voltage of a reference output generator 13. The adder 14 consists of a differential amplifier and an output corresponding to a difference between two input signals is obtained, The output of the adder 14 is inputted to a voltage control circuit 15a, in which a voltage required to correct the low frequency component is set. The voltage correcting the low frequency component is inputted to a tone control circuit 15b, from which an acoustic signal with the frequency characteristic whose low frequency component is emphasized is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an audio signal reproducing device, and particularly to an audio signal reproducing device suitable for a radio or television receiver.

(Prior Art) Conventional audio signal reproducing devices include, for example, tone control circuits that adjust the sound quality by increasing or decreasing the levels of low and high frequency components, and bass boost circuits that increase the level of low frequency components to emphasize bass. In addition, the loudness control circuit, which reduces the level of the midrange component and balances the level of the low and high frequency components, was also used.

These devices were equipped with a knob to adjust the level of the low or high frequency range, for example, and the listener turned this knob to adjust the sound quality to his or her preference. .

(Problem to be solved by the invention) However, when an acoustic signal is stopped again, the ratio of the level of the low range or the high range changes depending on the volume of the sound. The level of high frequencies was often insufficient, resulting in unnatural sound. Therefore, it was difficult for the listener to reproduce the desired sound quality without having to perform the troublesome operation of setting the volume of the sound using the volume knob and then adjusting the sound quality level using the sound quality adjustment knob.

The present invention was made in order to solve such problems, and its purpose is to provide an audio signal reproducing device that automatically increases or decreases the level of a part of the frequency band according to the loudness of the sound to optimize the sound quality. Our goal is to provide the following.

(Ding Dan to Solve the Problem) In order to solve the problem, the present invention provides the sound 'Jf (m
a filter that extracts a part of the frequency band of the acoustic signal; an adder that adds the output of this filter to a predetermined reference output; The invention is characterized in that it includes a variable frequency characteristic circuit that increases or decreases the level of the signal.

(Operation) A part of the frequency band is extracted by passing the acoustic signal through a filter. Next, this extracted output and a predetermined reference output are input to an adder. This adder outputs a signal with a level corresponding to the sum or difference of the human input signals. This output signal is input to a frequency characteristic variable circuit, and a part of the frequency band is increased or decreased in accordance with the level of this output signal, thereby changing the frequency characteristic of the acoustic signal.

(Example) Examples of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a block diagram of the tone control circuit of the audio signal reproducing apparatus according to the present invention, FIG. 2 is a block diagram of the bass boost circuit, and FIG. 3 is a block diagram of the loudness control circuit.

FIG. 1 shows a first embodiment of the present invention, in which an acoustic signal reproducing device 1 includes an LPF (low-pass filter) 11 that extracts low-frequency components of an acoustic signal, and an output waveform of this filter 11 that is shaped. A waveform shaping circuit 12, a reference output generator 13 that sets a reference voltage, and an adder 14 that adds the output of the waveform shaping circuit 12 and the output of the reference output generator 13.
and a frequency characteristic variable circuit 15 that increases or decreases the frequency characteristic of the mJ notation multiplied signal in accordance with the output level of the adder 14.
It is characterized by having the following.

The variable frequency characteristic circuit 15 includes a voltage control circuit 15a that controls the magnitude of the low frequency component according to the magnitude of the input from the adder 14, and a voltage control circuit 15a that controls the frequency characteristic of the low frequency range according to the output of the voltage control circuits 1 and 5a. Tone control circuit 1 that changes
5b.

Further, the output of this tone control circuit 1.5b is amplified by a conventional amplifier 16 and reproduced as sound by a speaker 17. Furthermore, this amplifier 16 and speaker 17
Although these are also used in the second and third embodiments to be described later, the same numbers are attached to FIGS. 2 and 3, and the explanation thereof will be omitted.

Next, the operation will be explained.

The acoustic signal is input manually to the tone control circuit 15b, while a part of this signal is input to the low-pass filter 11 to extract the low frequency component of this acoustic signal. This extracted low frequency component is converted into a DC voltage by the waveform shaping circuit 12, and together with the output voltage of the reference output generator 13, the adder 1
4 is input. The adder 14 is composed of a differential amplifier,
An output corresponding to the difference between these two input signals can be obtained. That is, the larger the difference, the larger the output. The output of this adder 14 is input to a voltage control circuit 15a, and a voltage required for correcting the low frequency component is set.

This voltage for correcting the low frequency component is input to the tone control circuit 15b and becomes an acoustic signal with frequency characteristics in which the low frequency component is emphasized.

This signal is amplified by the amplifier 14 and reproduced by the speaker 17 as a sound with emphasized bass.

Incidentally, the setting level of the reference output generator 13 may be set once to a desired level. That is, if it is desired to further emphasize the low frequency level, the set level may be increased. Level settings can be determined while actually listening to the playback sound.

Further, although the differential amplifier used in the adder 14 is constructed of a linear amplifier, it may be constructed of a non-linear amplifier such as a logarithmic amplifier.

In this embodiment, only the low frequency range is emphasized and the high frequency range is manually adjusted using the treble knob, but it is also possible to emphasize the high frequency range or the middle range.

FIG. 2 shows a second embodiment of the present invention, in which the acoustic signal reproducing device 2 includes an LPF (low-pass filter) 21, a waveform shaping circuit 22, a reference output generator 23, an adder 24, and a voltage control The present invention is characterized in that it includes a frequency characteristic variable circuit 25 composed of a circuit 25al and a bass boost circuit 25b.

The sound quality adjustment circuit that adjusts the sound quality of the low range and high range separately, or the sound quality adjustment circuit that adjusts the sound quality of the low range and high range, further emphasizes the level of the low range in accordance with the level of the low range. On the other hand, this audio signal reproducing device 2 has a sound quality adjustment circuit that emphasizes only the low frequency range, and further emphasizes the level of the low frequency range in accordance with the level of the low frequency range. It is. Therefore, although the acoustic signal reproducing device 2 has a difference in frequency characteristics from the bass boost circuit 25b or the 1-tone control circuit 15b, the voltage control circuit 25a sets the amount of correction for the low frequency range. are similar.

FIG. 3 shows a third embodiment of the present invention, in which the acoustic signal reproducing device 3 includes a BPF (band pass filter) 31, a waveform shaping circuit 32, a reference output generator 33, an adder 34, and a voltage control circuit. 35a and a loudness control circuit 35b.

While the audio signal reproducing device 1 is designed to further emphasize the sound quality of the low frequency region in the sound quality adjustment circuit that separately adjusts the sound quality of the low frequency region and the high frequency region, this audio signal reproducing device 3 is a loudness control circuit that attenuates the mid-range and strengthens the low-range and high-range. Therefore, the difference from the acoustic signal reproducing apparatus 1 is mainly a band-pass filter 31 that extracts mid-range components as a filter, and a variable frequency circuit 35 that includes a voltage control circuit 35a and a loudness control circuit 35b. Also, since the amount of attenuation is further emphasized in accordance with the level of the mid-range component,
The voltage control circuit 35a differs from the audio signal reproducing apparatus [1] and 2 in that the voltage control circuit 35a operates so that the greater the output of the adder, the greater the amount of attenuation in the middle range.

Note that low frequency or high frequency components may be detected.

(Effects of the Invention) As explained above, according to the present invention, a part of the frequency band of an acoustic signal is extracted, and the level of the part of the frequency band is increased or decreased in accordance with the extraction level. Therefore, even when the level of the acoustic signal is low, it is possible to reproduce the frequency characteristics in a state where the frequency characteristics are audibly close to flat. Further, even if the reproduction level of the audio signal is changed midway, the level of a part of the frequency band is always increased or decreased in accordance with the magnitude of the reproduction level, so there is no need to operate the sound quality adjustment knob each time.

35a... Voltage control circuit, 15b Heat control circuit, 25b... Bass boost circuit, 35b Loudness control circuit.

Claims (1)

[Claims] a filter that extracts a part of the frequency band of the acoustic signal, an adder that adds the output of this filter and a predetermined reference output, and a part of the frequency band of the acoustic signal that corresponds to the output level of the adder. An acoustic signal reproducing device comprising: a variable frequency characteristic circuit that increases/decreases the level of the sound signal.