JPS63234699A - Sound field correcting device - Google Patents

Abstract

PURPOSE:To adjust acoustic characteristic into a desired characteristic in a short period with high accuracy by measuring the acoustic characteristic of a reproduced sound field and providing a digital equalizer to realize an object characteristic at a listening point and calculating and setting a filter coefficient given to the digital equalizer so as to satisfy the relation of a linearity. CONSTITUTION:The titled device is provided with a measuring signal generator 1 generating a measuring signal to measure the acoustic characteristic of the listening point, an acoustic characteristic measuring device 8 measuring the acoustic characteristic and a control means 10 to set the filter coefficient obtained by an arithmetic means 9 to the digital equalizer 4. That is, the acoustic characteristic of a room is measured by the acoustic characteristic measuring instrument 8 and the linear phase FIR filter is obtained to realize the characteristic being the sum of the correction characteristic based on the transmission frequency wave characteristic obtained by the arithmetic means 9 and an optional characteristic and the obtained filter coefficient is set to the digital equalizer 4. Thus, the correction characteristic with high accuracy is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a sound field correction device for correcting the acoustic characteristics of a playback location.

2. Description of the Related Art Conventionally, as a method for correcting acoustic characteristics, there has been a second method in which actual acoustic characteristics are measured, a correction value is calculated based on the measured value, and the correction value is set in a correction device.

Most of them are laws.

In recent years, acoustic correction devices using digital filters have also been developed.

The conventional sound field correction device described above will be described below with reference to the drawings.

FIG. 4 shows the configuration of a conventional sound field correction device. In FIG. 4, 1 is an input section, 2 is a measurement signal generator, 3 is a switch for switching between input and measurement signals, 11 is a sound field corrector, 5 is an amplifier, 6 is a speaker, 7 is a microphone,
8 is an acoustic characteristic measuring device, 9 is a calculation means, and 10 is a control means.

Regarding the sound field correction device configured as described above, a method for correcting its acoustic characteristics will be described below.

First, in order to measure the acoustic characteristics of the playback location, the switch 3 is set to the B side, and a signal for measuring the acoustic characteristics is applied to the input section 1. Pink noise, impulses, warble tones, etc. are mainly used as measurement signals.

The sound field signal of the measurement signal input from the input section 1 passes through the sound field corrector 11, is amplified by the amplifier 5, and is reproduced from the 3-channel speaker 6. The reproduced signal that has entered the microphone 7 is analyzed by an acoustic characteristic measuring device 8 to determine the transmission frequency characteristic. The calculation means 9 calculates correction characteristics based on the three transmission frequency characteristics determined above so that the characteristics at the position of the microphone 7 become flat or desired characteristics. A method for determining the correction characteristic: G(eJω) when the target characteristic is flat will be described below.

When an analog equalizer is used as the sound field corrector 11, the correction characteristic is obtained as shown in the first equation.

IG(eJω)l=AVE-IH(ejω) I-...
-----(1) H(eJω): Transmission frequency characteristic AVE: Average sound pressure Here, IQ(e'ω)1 becomes the correction characteristic.

In addition, when a digital filter with an FIR type filter (hereinafter, a digital filter is assumed to be composed of an FIR type filter, and can be considered in the same way as an IIR type analog equalizer) is used as the sound field corrector 11, the measured The inverse transmission characteristic of the transfer function representing the transmission characteristic is determined, and this is inverse Fourier transformed to determine the filter coefficients to be set in the digital filter. (For example, "Application of convolution equalizer to compensation of waveform transfer characteristics of acoustic transmission system" by Neo et al., Proceedings of the Acoustical Society of Japan, October 1983) To obtain further arbitrary characteristics, it is necessary to obtain them by Hilbert transform. The filter coefficients are determined by inverse Fourier transform of the transmission characteristics. (For example, "About speaker simulation equipment" Seriyo et al. Institute of Electronics and Communication Engineers EA85-44
1985.10.24) Next, the control means 1o applies the obtained correction characteristics or filter coefficients to the sound field corrector 11.
Set to .

By performing the above operations, it is possible to listen with flat or desired frequency characteristics at the listening position.

FIG. 5 shows an example of correction.

Problems to be Solved by the Invention However, in the above configuration, when an analog equalizer is used as the sound field corrector 11, there is a disadvantage that accurate correction cannot be made due to the influence of adjacent bands. Also, when using a digital equalizer, it is necessary to accurately determine the sound pressure frequency characteristics including the phase at the listening point in order to perform waveform equalization, which requires a long measurement time9. 8 had the disadvantage that the equipment configuration became large-scale.

In view of the above drawbacks, the present invention obtains a linear phase type filter coefficient that realizes a correction characteristic based on the measured transmission frequency characteristic and an arbitrary characteristic, and sets it in the digital equalizer to shorten the time. The present invention provides a sound field correction device capable of reproducing sound with good correction accuracy in a timely manner.

Means for Solving the Problems In order to achieve the above object, the sound field correction device of the present invention includes a measurement signal generator that generates a measurement signal for measuring the acoustic characteristics of a listening point, and an acoustic signal generator that measures the acoustic characteristics. a characteristic measuring instrument;
The configuration includes control means for setting the filter coefficients determined by the calculation means in the digital equalizer.

Effect 6A-No The present invention measures the acoustic characteristics in the room using the acoustic characteristic measuring device with the above-described configuration, and calculates the correction characteristics based on the determined transmission frequency characteristics and the arbitrary characteristics using the calculation means. Calculation to obtain a linear phase FIR filter that realizes the added characteristics (for example, "Fundamentals of Digital Signal Processing J Pl 8B-
By setting the obtained filter coefficients in a digital equalizer, highly accurate correction characteristics can be obtained.

EXAMPLE An example of the present invention will be described below with reference to the drawings. Note that the same parts as in the conventional example shown in FIG. 4 are designated by the same numbers.

FIG. 1 shows the configuration of a sound field correction system in an embodiment of the present invention. In FIG. 1, 4 is a digital equalizer that corrects the acoustic characteristics.

The operation of the sound field correction device configured as described above will be explained below.

First, in order to measure the acoustic characteristics of the playback location,
.

Then, turn the switch 3 to the B side and apply a signal for measuring acoustic characteristics from the measurement signal generator 2 to the input section 1. Impulse and pink noise are used as measurement signals.

There are warp tones, etc., and you can use anything.

A measurement signal input from the input section 1 passes through a digital equalizer 4 and is reproduced from nine speakers 6.

The reproduced signal that has entered the microphone 7 is analyzed by an acoustic characteristic measuring device 8 to obtain sound pressure frequency characteristics. Here, calculation means 8
The correction characteristic calculation method will be explained below.

In FIG. 2 showing the processing procedure, the transmission frequency characteristic of the measured sound field is expressed by IH(eJω)1.

First, in step 12, correction characteristics are determined. If the target sound pressure frequency characteristic at the listening point is IF(e'ω)1,
The absolute value IG(e'ω)1 of the correction characteristic is determined by the second equation % Next, in step 13, a linear phase transfer function that realizes the correction characteristic obtained in the previous step is determined.

In step 14, the correction characteristic obtained in step 13 is inversely Fourier transformed to obtain an impulse response of the transfer function, which is used as a filter coefficient to be set in the digital equalizer.

The obtained filter coefficients are set in the digital equalizer 4 by the control means 1°.

The correction characteristics are completed by the above operation, and by turning the switch 3 to the A side and inputting the audio signal to the input unit 1, the audio signal is subjected to real-time convolution processing by the digital equalizer 4, and the audio signal is flat or as desired at the listening position. It is possible to listen based on the frequency characteristics.

Effects of the Invention As described above, the present invention measures the acoustic characteristics of a reproduced sound field, provides a digital equalizer that achieves the target characteristics at the listening point, and sets the filter coefficients given to the digital equalizer so as to satisfy the linear phase. Since it is configured to perform calculations and settings, it is possible to adjust the desired acoustic characteristics with high precision in a short measurement time, and it is also possible to obtain reproduced sound with good sound image localization.

9, no

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a sound field correction device according to an embodiment of the present invention, FIG. 2 is a flowchart showing the sound field correction method, and FIG.
4 is a block diagram of a conventional sound field correction device, and FIG. 5 is a characteristic diagram showing a conventional correction example. 1...Measurement signal generator, 4...Digital equalizer, 8...Acoustic characteristic measuring device, 9...
...Calculating means, 1o...Controlling means. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 3
Figure 2 (of) 4 threads (b) Number of filter 4 threads

Claims (1)

[Claims] A measurement signal generator that generates a signal for measuring the acoustic characteristics of a room, a digital equalizer that corrects the sound field, an acoustic property measuring device that measures the acoustic characteristics of the room, and a correction based on the measured values. Linear phase type FIR that realizes the characteristics
A sound field correction device comprising: arithmetic means for calculating a filter coefficient; and a control means for setting the filter coefficient to the characteristics of the digital equalizer.