JP2000134051A - Compressor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform compression that is suitable to listener's feeling by providing the preceding stage of a signal level detecting means with a filter whose frequency characteristic is similar to a human auditory sense. SOLUTION: An output signal from a sound source 1 such as a CD player is inputted to a filter 9 and is filtered by the filter 9, and then, a level calculating part 8 detects a level as the input signal. The frequency characteristic of the filter 9 is set to a prescribed characteristic and is made to be a characteristic that is similar to a human auditory sense characteristic which has a peak around 4000 Hz. The output signal from the sound source 1 is also inputted to a delay circuit 2, is subjected to delay processing for processing time of the filter 9 and the part 8 in the circuit 2 and is outputted to a gain adjusting part 3. And, an acoustic signal inputted to the part 3 is amplified with an amplification factor corresponding to the input signal level calculated by the part 8. The output signal from the part 3 is inputted to a volume adjusting part 4 and an output signal level is adjusted.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a compressor used in a sound reproducing apparatus for compressing a dynamic range of a sound reproducing signal.

[0002]

2. Description of the Related Art In a sound reproducing apparatus, if the dynamic range of a sound source such as a CD player is wide, that is, if the difference between a loud sound and a small sound is large, the distortion exceeds the allowable input of the power amplifier at a high signal level. When headphones are used, there is a problem that a large sound volume adversely affects the ears. Conversely, in a portion where the signal level from the sound source is low, a problem such as inaudibility of the sound occurs. As a method of solving such a problem, there is a method of using a compressor that compresses a dynamic range according to an input signal level.

FIG. 7 is a block diagram showing an example of a conventional compressor. The level of the input signal from the sound source 51 is detected by the level calculation unit 53, and the output signal of the sound source 51 is subjected to delay processing for the processing time of the level calculation unit 53 by the delay circuit 52, and then gain adjustment is performed. Input to the unit 54. Then, the acoustic signal input to the gain adjustment unit 54 is amplified at an amplification factor corresponding to the input signal level calculated by the level calculation unit 53 (the higher the input signal level, the lower the amplification factor). The power is amplified by the amplifier 55 and output from the speaker 56 as sound. In other words, according to the compressor,
Smaller sounds are louder and louder sounds are smaller and the dynamic range is compressed.

[0004]

However, the human audibility characteristic is not flat in the entire frequency range of the audio signal.
This is a characteristic having a peak around 4000 Hz (it sounds the loudest even with the same sound pressure). For this reason, if the compression is controlled by the signal level in the entire frequency range of the audio signal, there is a problem that the control does not match the human sense of hearing. For example, 2000 is almost inaudible to humans
When the signal level of 0 Hz is high, if the control according to the signal level of the entire frequency range of the audio signal is performed, as a result, the control is performed according to the signal almost inaudible to humans, and the control is not appropriate. Problems arise.

[0005] The present invention has been made in view of the above problems, and has as its object to provide a compressor that achieves characteristics suitable for human senses.

[0006]

Means for Solving the Problems and Effects There is provided a compressor (1) according to the present invention, comprising: a signal level detecting means for detecting a signal level of an input signal;
Compression means for compressing the input signal at a compression rate according to the signal level detected by the signal level detection means, in a stage prior to the signal level detection means, It is characterized in that it has a filter having a frequency characteristic similar to human hearing characteristics.

[0007] According to the compressor (1), the compression process is performed in consideration of not only the signal level of the input signal but also the characteristics of human sensation. Can be realized.

[0008] A compressor (2) according to the present invention.
Is characterized in that in the compressor (1), there is provided a characteristic switching unit for switching a frequency characteristic of the filter in accordance with a volume adjustment amount of a volume adjustment unit for adjusting a volume of an output sound. According to the compressor (2), in addition to the compression processing that also takes into account the characteristics of human sensation,
Further, processing based on the volume adjustment amount of the volume adjustment means is also performed, and compression processing is also performed in consideration of frequency characteristics with respect to the volume of human hearing, so that a compressor that performs compression more suited to the listener's feeling is realized. Can be.

[0009] The compressor (3) according to the present invention.
The compressor (1) is characterized in that the compressor (1) includes a compression change width switching means for switching a change range of a compression ratio in the compression means in accordance with a volume adjustment amount of a volume adjustment means for adjusting a volume of an output sound. I have. According to the compressor (3), the low-level signal is greatly increased in level. For example, when the compressor (3) is used in a sound reproducing apparatus, the reproduced sound of the low-level signal is missed. Can be prevented.

[0010] A compressor (4) according to the present invention.
The frequency characteristic similar to the inverse characteristic of the human audibility characteristic according to the signal level detected by the signal level detecting means in any one of the compressors (1) to (3). And a characteristic adding means for adding to the output signal of the means. According to the compressor (4), the output signal of the compression means is provided with an inverse characteristic of the frequency characteristic in human hearing, so that the effect of human hearing is totally eliminated, and the sense of the listener is further improved. A compressor that performs a suitable compression process can be realized.

[0011] Further, the compressor (5) according to the present invention.
The compressor (4) is characterized in that the compressor (4) is provided with a characteristic correcting means for correcting the frequency characteristic of the characteristic adding means in accordance with the volume adjustment amount of the volume adjusting means for adjusting the volume of the output sound. According to the compressor (5), the inverse characteristic of the frequency characteristic in human hearing is given, and the inverse characteristic is corrected according to the frequency characteristic of the volume in human hearing. A compression process taking into account the characteristics is performed, and a compressor that performs compression more suited to the listener's feeling can be realized.

[0012]

Embodiments of the present invention will be described below. FIG. 1 is a block diagram showing a configuration of an audio device including a compressor according to an embodiment of the present invention.

An output signal from a sound source 1 such as a CD player is input to a filter 9 and is filtered by the filter 9. Then, a level calculator 8 detects a level as an input signal. The frequency characteristic of the filter 9 is set to, for example, a characteristic as shown in FIG.
The characteristic is similar to the human auditory characteristic having a peak near 000 Hz. In other words, the frequency characteristics shown in FIG. 2 (A) show the human auditory characteristics at a certain signal level (set to an average level when listening to music etc.) Can be heard at the same volume). The filter 9 is constituted by a digital signal processing circuit using a digital signal processor or the like. The level calculation unit 8 is configured by a digital signal processing circuit that calculates the average value of the output signal of the filter 9 by digital arithmetic processing. The filter 9 can be realized by a resonance circuit including a capacitor, a coil, a resistor, and the like.
Further, the level calculating section 8 can be constituted by a detection circuit for performing envelope detection on the output signal from the filter 9, a rectifying and smoothing circuit for rectifying and smoothing the envelope detection signal, and the like.

The output signal from the sound source 1 is input to the delay circuit 2, where the delay signal is subjected to delay processing for the processing time of the filter 9 and the level calculation unit 8, and the gain adjustment unit 3
Output to The acoustic signal input to the gain adjustment unit 3 is amplified at an amplification factor according to the input signal level calculated by the level calculation unit 8 (the higher the input signal level, the lower the amplification factor). This gain adjustment unit 3
An output signal from the level calculation unit 8 is constituted by a variable amplification factor amplification circuit (or a variable attenuation factor attenuation circuit) applied to the amplification factor control terminal. This is realized by an electronic volume or the like composed of a ladder resistance or the like whose attenuation rate changes according to a terminal input signal.

The output signal from the gain adjuster 3 is input to a volume adjuster 4 composed of an electronic volume, and the output signal level is adjusted (the entire frequency band is uniformly attenuated). The amount of attenuation of the volume control unit 4 is controlled by a volume control signal from a microcomputer (microcomputer) 10. Note that the volume adjustment signal from the microcomputer 10 is output according to a signal from the operation unit 11 including a push button or the like, that is, a state of operation of the operation unit 11 by a user. After that, the output signal from the volume control unit 4 is power-amplified by the power amplifier 5 and output from the speaker 6 as sound.

Also, the microcomputer 10 outputs a characteristic switching signal (data for the digital signal processing circuit to realize the frequency characteristic) for instructing the filter 9 to switch the frequency characteristic in accordance with the volume adjusting signal to the volume adjusting unit 4. Do)
Is output to the filter 9. Then, the filter 9 receiving this characteristic switching signal responds to the characteristic switching signal as shown in FIG.
The characteristics are switched to the frequency characteristics shown in FIG. The frequency characteristic shown in FIG. 2B is similar to the frequency characteristic for the volume of human hearing, and indicates that the lower the volume, the more difficult it is to hear low and high tones (the sound in each band is the same sound). A psychological quantity indicating the actual volume feeling of each band at the pressure level is displayed for each overall volume level). Note that data for controlling these frequency characteristics is stored in the memory of the microcomputer 10.

Therefore, according to the compressor according to the first embodiment, as shown in FIG. 2 (B), the filter 9 has a frequency in human perception that low and high tones become harder to hear as the volume becomes lower. It is possible to obtain an output having a change characteristic in accordance with the characteristic change and reflecting a change in the sensitivity of human hearing due to the volume. As a result, the gain adjustment unit 3 performs volume control mainly on the signal level of the frequency band of the input signal which is often heard by humans. Therefore, according to the compressor according to the first embodiment,
The compression processing is performed in consideration of not only the signal level of the input signal but also the characteristics of human sensation, and it is possible to perform compression processing suited to the listener's sensation.

Next, a second embodiment of the present invention will be described. FIG. 3 is a block diagram showing an acoustic device including the compressor according to the second embodiment. Note that the same components as those of the audio device according to the first embodiment of the present invention shown in FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted.

In the second embodiment, the microcomputer 10 controls the level calculator 8 to switch the range of change in the compression ratio in response to the volume control signal to the volume controller 4. A predetermined calculation data signal (output to the level calculation unit 8) is output so that the gain adjustment unit 3 performs an operation of switching the change range of the compression ratio. The gain adjuster 3 responds to this compression change width switching signal by
The characteristics are switched to the input / output characteristics as shown in FIG. The input / output characteristic shown in FIG. 4B shows a characteristic in which the change range of the compression ratio is widened (the dynamic range is largely shifted to a high level side) as the volume control becomes lower.

Therefore, according to the compressor according to the second embodiment, in addition to the effect of the compressor according to the first embodiment, the level increase of the low-volume sound is output larger, and the low-volume sound is output. Can be prevented from being missed.

Next, a third embodiment of the present invention will be described. FIG. 5 is a block diagram showing a configuration of an audio device including a compressor according to the third embodiment.
Note that the same components as those of the compressor according to the first and second embodiments of the present invention shown in FIGS. 1 and 3 are denoted by the same reference numerals, and description thereof will be omitted.

In the third embodiment, an equalizer (EQ) 12 for adjusting the frequency characteristic of the output signal from the gain adjustment unit 3 is provided at the subsequent stage of the gain adjustment unit 3. The EQ 12 is constituted by a digital signal processing circuit using a digital signal processor or the like, and has an inverse characteristic of a frequency characteristic with respect to each volume in human hearing (similar to a so-called loudness circuit used in a sound reproducing device) as shown in FIG. Characteristic). The EQ 12 can also be realized by a resonance circuit including a capacitor, a coil, a resistor, and the like.

The microcomputer 10 outputs a compression change width switching signal for instructing the level calculator 8 to switch the compression ratio change range in accordance with the volume control signal to the EQ 12. The gain adjusting section 3 switches the characteristics to the input / output characteristics as shown in FIG. 4B in accordance with the compression change width switching signal. Further, the microcomputer 10 switches the characteristics of the EQ 12 to the characteristics as shown in FIG. 6, that is, the characteristics of increasing the bass and treble levels as the volume is adjusted to be lower, according to the volume adjustment signal to the EQ 12.

Therefore, according to the compressor according to the third embodiment, in addition to the operation of the compressor according to the second embodiment, the frequency characteristic of the output reproduced sound is adjusted according to the volume adjustment amount. Sound reproduction more suited to the listener's feeling can be performed.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of an audio device including a compressor according to a first embodiment of the present invention.

FIGS. 2A and 2B are frequency characteristic diagrams showing frequency characteristics of a filter.

FIG. 3 is a block diagram showing a configuration of an audio device including a compressor according to a second embodiment of the present invention.

FIGS. 4A and 4B are characteristic diagrams illustrating frequency characteristics of a filter and input / output characteristics of a gain adjustment unit.

FIG. 5 is a block diagram showing a configuration of an audio device including a compressor according to a third embodiment of the present invention.

FIG. 6 is a frequency characteristic diagram showing a frequency characteristic of the equalizer.

FIG. 7 is a block diagram showing an example of a conventional compressor.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Sound source 2 ... Delay circuit 3 ... Gain adjustment part 8 ... Level calculation part 9 ... Filter 10 ... Microcomputer

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Hideki Matsui 1-2-28 Goshodori, Hyogo-ku, Kobe-shi, Hyogo F-term in Fujitsu Ten Limited (Reference) 5D020 CE03 5D045 AB30 5J030 BA03 BB00 BC00 BC02 BC07 BC08 BC11

Claims (5)

[Claims] 1. A signal level detecting means for detecting a signal level of an input signal, and a compressing means for compressing the input signal at a compression rate corresponding to the signal level detected by the signal level detecting means. A compressor comprising: a filter having a frequency characteristic similar to a human audibility characteristic in a stage preceding the signal level detecting means. 2. The compressor according to claim 1, further comprising a characteristic switching unit that switches a frequency characteristic of the filter in accordance with a volume adjustment amount of the volume adjustment unit that adjusts a volume of the output sound. 3. The apparatus according to claim 1, further comprising: a compression change width switching unit that switches a range of a change in a compression ratio of the compression unit according to a volume adjustment amount of the volume adjustment unit that adjusts a volume of the output sound. The described compressor. 4. A characteristic adding means for adding, to the output signal of the compression means, a frequency characteristic similar to an inverse characteristic of a human auditory characteristic according to the signal level detected by the signal level detection means. 4. The method according to claim 1, further comprising:
The compressor according to any one of the above items. 5. The compressor according to claim 4, further comprising a characteristic correction unit for correcting a frequency characteristic of said characteristic adding unit in accordance with a volume adjustment amount of a volume adjustment unit for adjusting a volume of an output sound. .