JPS62166698A - Automatic sound field correcting device - Google Patents

Abstract

PURPOSE:To correct a sound field in a comfortable condition by comparing Fourier transformation values at every frequency band of the sound signal from an acoustic source with the output of a microphone to operate a graphic equalizer and controlling the sound pressure level of a speaker to a prescribed characteristic. CONSTITUTION:The sound signal from the acoustic sources 11-14 is made acoustic by the speaker 25 through the common contact 20, of a change-over switch 15, a variable resistor 21, the graphic equalizer 22 and a amplifier circuit 24. The electric signal from the microphone 26 is amplified by an amplifier circuit 27 and digitally converted by an A/D converter 28 and the sound signal from the common contact 20 is digitally converted by an A/D converter 30 and respectively supplied to a high speed Fourier transformer 29. Then, an arithmetic is carried out for a prescribed time in a processing circuit 31, a control signal is supplied to the equalizer 22 through a line 23 and the signal at every band of the plural frequency is increased and decreased. Thus, the sound pressure level conducted from the speaker 25 can be set to a predetermined characteristic throughout all the frequency bands.

Description

DETAILED DESCRIPTION OF THE INVENTION TECHNICAL FIELD The present invention relates to an automatic sound field correction device used in a single room of an automobile, a listening room, and the like.

Background Art Even if the sound pressure level generated from a speaker in a single room or listening room of a car is flat over the entire frequency band, the acoustic frequency characteristics at the listening point vary due to the influence of standing waves and reflected waves. (produces peaks and dips.

A prior art technique for solving this problem and making the acoustic frequency characteristics flat at the listening point is shown in FIG. Audio signals from a radio receiver, a magnetic tape cassette playback device, etc., and noise from a noise generator 2 are supplied from a changeover switch 3 to a graphic equalizer 4, and are applied to each of a plurality of frequency bands. The audio signal is amplified or attenuated, is amplified by the amplifier circuit 5, and the speaker 6 is driven. A microphone 7 is placed at the listening point and converts the sound from the speaker 6 into an electrical signal. The output from the microphone 7 is amplified by 1M by an amplifier circuit 8, converted to a digital value by an analog/digital converter, and given to a processing circuit 10 realized by a microcomputer or the like. The processing circuit 10 operates the graphic equalizer 4.

Referring to FIG. 5, the operation of the previous ite technique shown in FIG. 4 will be explained. Moving from step n1 to step 112,
The changeover switch 3 applies a signal such as pink noise or white noise from the noise generator 2 to the graphic equalizer 4 through its contact B. The noise from the noise generator 2 has a flat level over the entire frequency band.

The microphone 7 receives the sound from the speaker G, and adjusts each frequency band of the graphic equalizer 4, that is, the pan r.
The difference from each standard level is corrected and calculated in step +14. In step 5, the processing circuit 10 operates the graphic equalizer 4 so that the noise transmitted through the contact B of the changeover switch 3 can be received by the speaker G at a flat sound pressure level over the entire frequency band. . When it is determined in step n6 that the sound from the speaker G has a flat sound pressure level over the entire frequency band, the process moves to step n7, and the switching mode of the changeover switch 3 is changed to transmit the sound from the sound qJ source through the contact A. The audio signal from 1 is applied to the graphic equalizer 4, and the operation ends at step n8.

Problems to be Solved by the Invention In such prior art, during the period when the noise signal from the noise generator 2 is applied to the graphic equalizer 4 by the changeover switch 3 and the noise sound is generated from the speaker 6, The listener must listen to the noise until the processing circuit 10 completes the correction of the graphic equalizer 4, which is very unpleasant.

An object of the present invention is to provide an automatic sound field correction device that allows sound field correction to be performed in a comfortable condition without hearing noise.

Means for Solving the Problems The present invention provides a speaker that is interposed between a sound source and a speaker that converts the sound signal from the sound V source into sound, receives a control signal, and generates a sound signal for each of a plurality of frequency bands. a graphic equalizer that enhances or attenuates the sound; a microphone that converts the audio from this speaker into an electrical signal; and a microphone that converts the audio signal from the acoustic source and the output of Means for controlling the sound pressure level of the speaker to have predetermined characteristics over all 1.1 wave number bands by performing Fourier transform and operating a graphic equalizer by comparing the Fourier transform values for each frequency band listed in 11q. An automatic ￥f field correction device is characterized in that it includes the following.

According to the present invention, the sound? Ir1. While a loud voice is being converted into sound by a speaker, a graphic equalizer is operated, and the sound pressure level from the speaker is controlled to have predetermined characteristics over the entire frequency band. . Therefore, as mentioned in connection with the prior art, the person receiving the noise does not hear the noise.
Sound field correction is performed comfortably.

Embodiment FIG. 1 is a block diagram of an embodiment of the present invention. Audio signals from the amplitude modulation broadcast receiving circuit 11, the frequency modulation broadcast receiving circuit 12, the magnetic tape cassette playback device 13, and the compact disk playback device 14, which are sound sources, are respectively given to one of the individual contacts 16 of the changeover switch 15. . The audio signal from the common terminal α20 of the changeover switch 15 is applied to a graphic equalizer 22 via a variable resistor 21. The graphic equalizer 22 is
A control signal is received on the line 23, and the audio signal for each of a plurality of frequency bands is enhanced or mounted.

The audio signal from the graphic equalizer 22 is amplified by the amplifier circuit 24 and turned into sound by the speaker 25.

The sound from the speaker 25 is converted into an electrical signal by the microphone 2G provided at the listening point. The electrical signal from the microphone 26 is amplified by an amplifier circuit 27, converted into a digital value representing a frequency by an analog/default converter 28, and then given to two fast Fourier transformers to be Fourier transformed.

The audio signal from the common contact 20 of the changeover switch 15 is
In addition to being applied to the variable resistor 21 as described above, it is also applied to the analog/deftal converter 30 and converted into a digital value, and this digital value is also applied to the fast Fourier transformer 2.
given to 9. The output from the fast Fourier transformer 29 is sent to a processing circuit 31. Processing circuit 31 provides control signals to graphic equalizer 22 via line 23.

The transfer function of the transfer characteristic including the speaker 25 is 14(f)
When the signal input to the speaker 25 is x (r) and the signal picked up by the microphone 2G is Y ("), Y (f) = X (f) - H (f)
・It can be expressed as (1). In this manner, using fast Fourier transform, the transfer function H(f) can be determined from the audio signal from the microphone 20 and the audio signal from the microphone 2G after the changeover switch 15 is common. According to two fast Fourier transformers, α of music etc.
Even if the signal waveform is random like a true signal, a fast Fourier transform is performed in real time to obtain the transfer function H(f) between the common contact point 20 and the microphone 26.
can be found.

This transfer function 1((r)) is calculated and obtained in the processing circuit 31.

Generally, a music signal does not necessarily include components of all frequency bands in a short period of time, so the processing circuit 31 performs calculations over a predetermined period of time, for example, about 20 to 60 seconds, thereby transmitting all frequency bands. Interval IH (f)
can be found.

Based on the transfer function H(f) determined in the processing circuit 31, the processing circuit 31 provides a control signal to the graphic equalizer 22 via the line 23, thereby enhancing the signal of each of the plurality of frequency bands of the graphic equalizer 22. and decrease.

As a result, the sound pressure level derived from the speaker 25 can have a predetermined characteristic, for example, a flat characteristic over the entire frequency band.

The operating circuit 32 provides a switching source signal via a line 33;
This switching signal causes selective switching between the common contact 20 and the individual contacts 16 to 19 of the switch 15. The processing circuit 31 performs arithmetic processing operations on the Fourier transform results in one frequency band shown in Table 1 of the audio signals derived from the receiving circuits 11.12 and the reproducing devices 13.14. As a result, it is possible to quickly complete the pruritus treatment without performing arithmetic processing operations over a wide band unnecessarily.

The operation will be explained with reference to FIG. Moving from step theory 1 to step 1112, the analog/digital converters 28 and 30 perform an analog/digital conversion operation, and in step m3, the fast Fourier transformer 29 performs a fast 7-tier conversion operation. step +64
Then, as mentioned above, it is determined whether a period of, for example, 20 to 60 seconds has elapsed, and if so, step gloss 5 is determined.
Next, the difference between each frequency band, that is, each band, with respect to the standard level of the sound pressure level of the blind tube from the speaker 25 is corrected, and the transfer function H(f) is obtained.

In step 1116, the graphic equalizer 22 is operated based on the calculation result of step C115 described above. In step m7, it is determined whether the sound pressure level of the speaker 25 matches the target level 1 which is the standard level.
If so, in step m8 the control is
Complete one operation.

FIG. 3(1) shows the frequency spectrum of the transfer characteristic obtained by the fast Fourier transformer 29 based on the electrical signal from the microphone 26 in the embodiment shown in FIGS. 1 and 2. FIG. High frequencies above frequency r1 are not included in the audio signals from the receiving circuit 11.12 and playback device 13.14 as shown in Table 1, and therefore the upper limit frequency r1 shown in Table 1 is At the above frequency, no calculation is performed in the processing circuit 31, and the graphic equalizer 22 is not controlled.

This allows calculation processing to be completed in a short time.

FIG. 3(2) shows the frequency spectrum of an electrical signal that reproduces a noise sound by the speaker 7 in the prior art described in connection with FIGS. 4 and 5 above. The noise signal from the noise generator 2 has frequency components over a wide frequency band, so regardless of the type of acoustic source 1,
A problem arises in that arithmetic processing is performed over an unnecessarily wide frequency range, resulting in long operating times.

In the embodiment described above, since the graphic equalizer 22 is controlled below the upper limit frequency shown in Table 1, it is possible to perform sound field correction in a short time.

The present invention can be implemented in a wide range of spaces such as the space t inside the passenger compartment of a private car, and a general driving room.

Effects As described above, according to the present invention, sound field correction is performed over a predetermined period of time when an audio signal from a sound source is being reproduced, so there is no need to listen to noise sounds as in the prior art. Comfortable sound field correction can be performed.

[Brief explanation of drawings]

FIG. 1 is a block diagram of one embodiment of the present invention, and FIG. 2 is a block diagram of an embodiment of the present invention.
70-Chart for explaining the operation of the illustrated embodiment, P
Figure t53 is a diagram showing the frequency spectrum showing the transmission characteristics of the electrical signal reproduced by microphone 7.201,
FIG. 4 is a block diagram showing the configuration of the prior art, and FIG. 5 is a flow chart explaining the operation of the prior art. 11... Amplitude modulation broadcast receiving circuit, 12... Frequency modulation broadcast receiving circuit, 13... Magnetic tape cassette playback device, 14... Compact disk playback device, 15.
...Selector switch, 21...Variable resistor, 22...
- Graphic equalizer, 24.27... Amplification circuit, 25-0. Speaker, 26...Microphone, 28
．． 30...Analog/analog converter, 29, -, Fast Fourier transformer, 31...Processing circuit, 32...Operation circuit Agent Patent attorney Keibu Saikyo Figure 2 Figure 4vA Figure 5

Claims (1)

[Scope of Claims] A graphic that is interposed between a sound source and a speaker that converts the sound signal from the sound source into sound, and that receives a control signal and amplifies or attenuates the sound signal for each of a plurality of frequency bands. An equalizer, a microphone that converts the audio from this speaker into an electrical signal, and performs fast Fourier transform on the audio signal from the acoustic source and the output from the microphone over the entire frequency band for a predetermined time, and An automatic sound field correction device comprising means for operating a graphic equalizer by comparing Fourier transform values and controlling the sound pressure level from a speaker to have predetermined characteristics over the entire frequency band.