JP2541062B2 - Sound reproduction device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sound reproducing device for adjusting the characteristics of an acoustic signal according to the characteristics of ambient noise. The present invention also relates to a sound reproducing device used for correcting frequency characteristics of an amplifier, a speaker, and a listening room.

[0002]

2. Description of the Related Art Generally, in a vehicle-mounted audio device used by being loaded in an automobile or the like, a noise level in a passenger compartment, which is a listening space, changes depending on a running condition of the automobile or the like. However, the level of the audio signal to be listened to was too high or too low as compared with the ambient noise, and it was difficult to listen to the comfortable audio signal. For this reason, an automatic volume control circuit that automatically controls the output volume of an audio signal according to the ambient noise level has come to be used in this type of audio device.

[0003] In addition, loudness correction technology for correcting the human auditory perception characteristics, in which the sensitivity is lowered particularly in a low frequency region and a high frequency region at a low sound volume, the frequency characteristic is corrected according to the listening environment, or according to the listener's preference. Equalizing technology for amplifying only a desired frequency band is well known.

[0004]

In the above-described automatic volume control circuit of the on-vehicle audio apparatus, the volume of the audio signal emitted from the speaker is increased by increasing the gain of the volume control circuit more than the amount of noise in hearing. Has the drawback of increasing the noise and giving the listener an unnatural feel. For example, the noise in the passenger compartment during traveling on a gravel road has a characteristic that the level becomes higher as the frequency becomes lower, and in the volume control circuit, the level of the audio signal emitted from the speaker is changed according to the total noise level. Although the volume is controlled so as to be simply increased over the entire frequency band, the sensitivity of the listener's human ear decreases as the frequency of the sound to be heard decreases. Therefore, if the volume is excessively increased, the level is too high, especially in the high frequency range, giving an unnatural feeling. Further, the frequency characteristic of the reproducing device system (amplifier, speaker, listening room) is not flat, and there is no means for actively correcting this.

Further, the loudness correction technique and the equalizing technique have a drawback that they cannot deal with ambient noise in real time. The present invention solves the above-mentioned problems of the prior art, considers the human hearing characteristics, corrects the nonlinearity of the frequency characteristics of the playback device system (amplifier, speaker, listening room), and reduces the ambient noise. It is an object of the present invention to provide a sound reproduction device capable of correcting the characteristics of a sound signal by following changes in the real time.

[0006]

According to the present invention, an external sound capturing means for capturing sound emitted from a sound generating means such as a speaker and ambient noise, and an acoustic signal from the external sound capturing means are provided. , The basic audible limit curve by analyzing the acoustic signal for each different frequency band
Noise or reproducing system (amplifier, a speaker, the listening room) and external sound audibility characteristic calculation means for outputting to extract components above this correction audible limit curve with obtaining a corrected audible limit curve masking effect is taken into account by the acoustic signal Source, an equalizer that amplifies the acoustic signal provided from the acoustic signal source for each different frequency band, and analyzes the acoustic signal provided from the acoustic signal source for each different frequency band, and a component that exceeds the basic audible limit curve is analyzed. Acoustic signal auditory sensation characteristic calculating means for extracting and outputting; and comparing means for comparing the output of the external sound auditory sensation characteristic calculating means with the output of the acoustic signal auditory sensation characteristic calculating means. According to the comparison result of the comparing means, It is characterized by controlling the equalizer.

[0007]

[Action] external sound According to the arrangement hearing sensitivity calculating ambient noise or reproduction system by means (amplifiers, speakers, listening room) masking effect is taken into account complement
An acoustic component (actually audible acoustic component) that exceeds the positive audibility limit curve is extracted. Further, the acoustic signal audibility characteristic calculating unit extracts a component (a component that can be heard by a human when there is no noise or distortion of the reproduction system) that exceeds a general human basic audible limit curve. The amount attenuated by noise is detected by comparing the calculation results of the two auditory characteristic calculation means. By controlling the characteristics of the equalizer in accordance with the comparison result, an acoustic signal that is compensated for the influence of external noise (including distortion in the frequency characteristics of the listening room, the speaker, and the amplifier) is emitted. And
The comparison process, since the equalizer characteristic control is performed for different frequency bands, never originally human hearing characteristic as in the conventional automatic volume control circuit will be amplified to the level of the frequency component inaudible due. Where the basic audible
The limit curve is the generally known human hearing characteristic.
Considered the audible limit curve (see, for example, FIG.
This means that the corrected audible limit curve is the basic
External noise on the audible limit curve (human audible limit curve)
Depends on the playback system (amplifier, speaker, listening room)
Audible limit curve with masking effect
(Corresponding to FIG. 2B)).

[0008]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing a sound reproducing device according to an embodiment of the present invention. In this figure, 1
Is an audio signal source that generates an audio signal, such as an audio tape player, a compact disc player, a radio receiver, and a transceiver. Reference numeral 2 denotes an equalizer, which amplifies an acoustic signal supplied from an acoustic signal source independently for each frequency band according to a control signal described later. 3 is a speaker 4
Is a power amplifier for driving, and 4 is a speaker.

Reference numeral 5 is a microphone for capturing the sound emitted by the speaker 4 and ambient noise. 6
Is a characteristic correction circuit for compensating the frequency characteristic of the microphone 5 with respect to the acoustic signal captured by the microphone 5.

Reference numeral 8 denotes an acoustic signal audibility characteristic calculation circuit, which extracts an acoustic signal component exceeding an audible limit curve in consideration of generally known human audibility characteristics. Specifically, the acoustic signal supplied from the acoustic signal source 1 is spectrally analyzed by FFT (Fast Fourier Analysis), the BPF similar to the equalizer 2 is arranged and spectrally analyzed, or each component detected by other means. Is compared to the value of the audible limit curve at the same frequency.

Reference numeral 7 denotes an external sound audibility characteristic calculation circuit, which inputs an acoustic signal taken in from the outside in which the frequency characteristic of the microphone 5 is compensated by the characteristic correction circuit 6 to input an external noise or a reproduction system (to a human audible limit curve). Amplifier, speaker,
Create an audible limit curve that takes into account the masking effect of the listening room) and extract components that exceed it. The masking effect is a large level signal (noise)
The small level signal component close to the component is inaudible to the human ear. This circuit regards a component other than the spectrum of the acoustic signal that exceeds the audible limit curve as noise based on the spectrum of the acoustic signal that exceeds the human audible limit curve given from the acoustic signal audibility characteristic calculation circuit 8, and determines that noise. The audible limit curve is corrected based on the components to obtain the audible limit curve with the masking effect added. Then, a component exceeding the audible limit curve to which the masking effect is added is extracted. The specific circuit configuration is almost the same as that of the acoustic signal auditory perception characteristic calculation circuit 8.

Reference numeral 9 denotes a comparison circuit, which has a component exceeding the human audibility limit curve given by the acoustic signal audibility characteristic calculation circuit 8 and a component exceeding the audibility limit curve given the masking effect given by the external sound audibility characteristic calculation circuit. Is compared for each predetermined time and for each same band, and the absolute value of the difference is output.
Reference numeral 10 is an LPF (low-pass filter), which prevents the comparison result for each band from changing abruptly with time (the time constant is about 100).
ms). The signal subjected to the LPF processing for each band is equalizer 2
It becomes the control signal of each band.

Next, the operation of the sound reproducing apparatus shown in FIG. 1 will be described with reference to FIG. Here, in order to explain the operation in an easy-to-understand manner, it is assumed that the acoustic signal source 1 generates an acoustic signal having a single spectrum, and that ambient noise also has a single spectrum.

The solid line with an arrow in (a) shows a single-spectrum acoustic signal generated from the acoustic signal source 1. And
The curve (a) shows a generally known human audible limit curve. (C) is the output of the acoustic signal auditory characteristic calculation circuit 8, and the solid line with an arrow indicates the level of the acoustic signal exceeding the audible limit curve shown in (a), and an ideal listening space and an ideal noise-free space Sounds at this level if you use such a device.

The solid line with an arrow in (b) indicates that the sound emitted through the speaker 4 is captured by the microphone 5, and the dotted line with an arrow indicates that ambient noise is captured by the microphone 5. The curve shows an audible limit curve in which the masking effect by noise is added. In order to simplify the explanation, the operation explanatory diagram does not consider distortion of the frequency characteristics of the amplifier, the speaker, and the microphone.
(D) is the output of the external sound hearing characteristic calculation circuit 7, and the solid line with an arrow shows the level of the signal that exceeds the audible limit curve in which the masking effect by noise shown in (b) is taken into consideration, and is actually the human ear. It shows the level you hear.

(E) is the output of the comparison circuit 9, and (f)
Is to control the equalizer 2 according to the comparison result of the comparison circuit 9 to raise the acoustic signal component canceled by noise. As is clear from this figure, the audible gain does not change even if there is noise.

The present invention has been described above with reference to the embodiments. However, according to the present invention, not only the influence of external noise,
The distortion of the frequency characteristics of the amplifier and speaker can be corrected at the same time. When the source sound is stereo, frequency synthesis is performed using the synthesized sound of the L and R channels as the source sound, and the microphone may be arranged at a position where the L component and the R component can be evenly captured. In this case, instead of simply synthesizing the L and R channels into the source sound, they should be synthesized after being decomposed for each frequency domain.

[0018]

As described above in detail, in the present invention, the acoustic characteristics are controlled for each frequency band in consideration of the human hearing characteristics and the masking effect due to noise, so that unnecessary frequency bands are amplified. And don't give the listener an unnatural feeling. In addition, the actually emitted sound and surrounding noise or reproduction system (amplifier, speaker,
Real-time control is possible because the acoustic characteristics can be controlled according to the distortion of the listening room.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of an embodiment of the present invention.

FIG. 2 is a diagram for explaining the operation of the embodiment.

[Brief description of reference numerals]

DESCRIPTION OF SYMBOLS 1 ... Acoustic signal source, 2 ... Equalizer, 3 ... Amplifier, 4 ... Speaker, 5 ... Microphone, 6 ... Microphone characteristic correction circuit, 7 ... External sound perception characteristic calculation circuit, 8 ... Acoustic signal perception characteristic calculation circuit, 9 ... Comparison Circuit, 10 ... Low-pass filter.

Claims (1)

(57) [Claims] 1. An external sound capturing means for capturing sound emitted from a sound generating means such as a speaker and ambient noise, and an acoustic signal from the external sound capturing means are provided, and the acoustic signals are provided in different frequency bands. by analyzing each, based on
This together with the noise also is properly in the audible limit curve to obtain the corrected audible limit curves consideration the masking effect by the reproduction system
An external sound perception characteristic calculating means for extracting and outputting a component exceeding the corrected audible limit curve, an acoustic signal source, an equalizer for amplifying an acoustic signal given from the acoustic signal source for each different frequency band, and an acoustic signal source from the acoustic signal source. An acoustic signal auditory characteristic calculating means for analyzing a given acoustic signal for each different frequency band, extracting and outputting a component exceeding the basic audible limit curve, an output of the external acoustic auditory characteristic calculating means and the acoustic signal auditory characteristic calculation Comparing means for comparing the output of the means, and controlling the equalizer according to the comparison result of the comparing means.