JPH07302099A - Audio signal analyzing device - Google Patents

Abstract

PURPOSE:To provide an audio signal analyzing device in which a high speed signal analysis is performed without depending on frequency. CONSTITUTION:Input audio signals are digitized by an A/D converter 3 employing the oscillation output of a synchronizing circuit 2 which is synchronized to the input audio signals and oscillates with the frequency, that is element number multiple of an FFT analysis, as a sample clock. The FFT analysis is performed relative to the input audio data obtained by the converter 3 by a digital signal processing section 4.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an audio signal analyzing device used as an audio circuit measuring device in audio visual equipment, multimedia equipment and the like, and particularly to a fast Fourier transform (FFT: FFT).
The present invention relates to an audio signal analysis device that performs audio analysis by ast Fourier Transform).

[0002]

2. Description of the Related Art This kind of audio signal analyzing apparatus is used for performing feature extraction of audio waveforms by performing single-time spectrum analysis, cepstrum analysis, etc. by FFT analysis by digital signal processing for audio signals. In this type of conventional audio signal analyzing apparatus, the main frequency of the input audio signal to be analyzed is measured, the filter is switched according to the frequency, and then the digital signal processing according to the frequency is performed.

[0003]

By the way, in the conventional audio signal analyzing apparatus as described above, it takes a long time to measure the main frequency of the input audio signal and switch the filter, and the frequency-dependent complex There was a problem that a different analysis program was required.

Therefore, in view of the conventional problems as described above,
It is an object of the present invention to provide an audio signal analysis device that can perform signal analysis at high speed without depending on frequency.

[0005]

In order to solve the above-mentioned problems, an audio signal analyzing apparatus according to the present invention comprises a synchronizing circuit which oscillates at a frequency which is equal to the number of elements of FFT analysis in synchronization with an input audio signal, An analog / digital converter that digitizes the input audio signal by using the oscillation output of the synchronizing circuit as a sampling clock, and input audio data that is obtained by digitizing the input audio signal by the analog / digital converter are F
And a digital signal processing unit for performing FT analysis.

[0006]

In the audio signal analyzing apparatus according to the present invention, the analog / digital converter uses the oscillation output of the synchronizing circuit that oscillates at a frequency that is the number of elements of the FFT analysis in synchronization with the input audio signal as a sampling clock. The signal is digitized and the input audio data obtained by this analog / digital converter is subjected to FFT analysis by the digital signal processing unit.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an audio signal analyzing apparatus according to the present invention will be described below with reference to the drawings.

The audio signal analyzing apparatus according to the present invention is
For example, as shown in FIG. 1, a synchronizing circuit 2 and an analog / digital (A / D) converter 3 to which an input audio signal is supplied via an input circuit 1, and the input audio signal by the A / D converter 3. And a digital signal processing unit 4 to which the input audio data obtained by digitizing is input.

Here, the input circuit 1 performs impedance matching with respect to a device under test which supplies an input audio signal and gain adjustment with respect to the input audio signal. The device under test is, for example, a disc reproducing device, and reproduces the test audio signal from a digital audio disc in which a sine wave signal of a predetermined frequency is recorded as a test audio signal, and the input circuit The signal is supplied to the synchronizing circuit 2 and the A / D converter 3 via 1.

The synchronizing circuit 2 is synchronized with the fundamental wave of the input audio signal supplied via the input circuit 1,
The number of elements of the FFT analysis in the digital signal processing unit 4 having the fundamental frequency f ₀ , for example, the frequency 102 times 1024 times.
It oscillates at 4f ₀ . Then, the synchronizing circuit 2 operates at the fundamental frequency 10 of the input audio signal.
An oscillation output having a frequency of 24 times 1024f ₀ is supplied to the A / D converter 3 as a sampling clock.

The A / D converter 3 uses the sampling clock supplied from the synchronizing circuit 2, that is, the sampling clock having a frequency 1024f _{0 which is} 1024 times the fundamental frequency f ₀ of the input audio signal. Digitize the input audio signal supplied via. The A / D converter 3 is obtained by digitizing the input audio signal 1
The input audio data of 024f ₀ rate is supplied to the digital signal processing unit 4.

The digital signal processing section 4 includes the A / D
1024f supplied from converter 3 ₀Enter rate
Temporarily store the audio data in the memory 5, and in this memory 5,
The stored input audio data is
FFT analysis of 1024 points by the CPU (CPU) 6
I am supposed to do it.

That is, in the audio signal analyzing apparatus of this embodiment, in synchronization with the fundamental wave of the input audio signal,
The number of elements of the FFT analysis on the fundamental frequency f ₀ (10
24) A sampling clock having a frequency of 1024f ₀ is generated by the synchronizing circuit 2, and the input audio signal is digitized by the A / D converter 3 using the sampling clock. 1 per fundamental wave in sync with the fundamental wave
Generate audio data by inputting 024 points. Then, the input audio data is subjected to FFT analysis of 1024 points per fundamental wave by the digital signal processing unit 4 to analyze distortion specification of the audio signal reproduced by the device under test.

As described above, in synchronization with the fundamental wave of the input audio signal, the synchronizing circuit 2 generates a sampling clock having a frequency of 1024f ₀ , which is the number of elements in the FFT analysis (1024) times the fundamental frequency f ₀ . As a result, in the A / D converter 3, there are 102
Input audio data of 4 points can be generated in synchronization with the fundamental wave of the input audio signal. Therefore, in the digital signal processing unit 4, since the input audio data supplied from the A / D converter 3 is synchronized with the fundamental wave of the input audio signal, 1024 points per fundamental wave for the input audio data. The FFT analysis can be accurately performed. Further, the digital signal processing section 4 only needs an analysis program for performing FFT analysis of 1024 points per fundamental wave, and can be simplified because it does not depend on the frequency of the input audio signal. Further, in the audio signal analyzing apparatus having such a configuration, it is possible to perform signal analysis at high speed without the need for frequency measurement and filter switching, and the circuit scale can be reduced, so that the apparatus can be downsized.

In the above description of the embodiment, the digital signal processing unit 4 performs FFT analysis of 1024 points for each fundamental wave, but the number of elements of FFT analysis in the audio signal analysis apparatus according to the present invention. Is not limited to the above 1024 points.

[0016]

As is apparent from the above description, in the audio signal analyzing apparatus according to the present invention, the oscillation output of the synchronizing circuit that oscillates at the frequency of the number of elements of the FFT analysis in synchronization with the input audio signal is sampled. As a clock
The input audio signal is digitized by the analog / digital converter, and the FFT analysis of the input audio data obtained by the analog / digital converter is performed by the digital signal processing unit. Can be subjected to a fast Fourier transform (FFT) without performing frequency measurement and filter switching, and does not require a high-speed frequency-dependent complicated analysis program.

Therefore, according to the present invention, it is possible to provide an audio signal analyzing apparatus which can perform signal analysis at high speed and accurately without depending on frequency.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of an audio signal analysis device according to the present invention.

[Explanation of symbols]

 1 Input Circuit 2 Synchronous Circuit 3 A / D Converter 4 Digital Signal Processor 6 Memory 7 Computer

Claims (1)

[Claims] 1. A synchronizing circuit that oscillates at a frequency that is a multiple of the number of elements of FFT analysis in synchronization with an input audio signal, and an analog / digital conversion that digitizes the input audio signal using an oscillation output of the synchronizing circuit as a sampling clock. An audio signal analyzing apparatus comprising: a converter and a digital signal processing unit that performs FFT analysis on input audio data obtained by digitizing the input audio signal by the analog / digital converter.