JP6648002B2 - Sound equipment timbre characteristic evaluation apparatus and timbre characteristic evaluation method - Google Patents

Description

  The present invention relates to an apparatus for analyzing and evaluating the timbre characteristics of audio equipment.

  An audio analyzer is a measuring instrument for quantifying sound quality, and generally has a function such as a distortion meter, a frequency counter, an AC voltmeter, a DC voltmeter, an FFT analyzer, and a low distortion audio signal source. .

  The problem to be solved is that the evaluation of the timbre by the conventional audio analyzer is not sufficient. Conventional audio analyzers do not attach importance to relative phase angles, and cannot sufficiently evaluate the timbre of audio equipment. Therefore, at present, evaluation of timbre relies on human hearing, which lacks objectivity.

  An original sound wave can be considered as a product obtained by superimposing a fundamental wave composed of a sine wave and a harmonic having a frequency that is an integral multiple of the fundamental wave according to Fourier transform theory.

As a basic characteristic of the sound, pitch, volume, but it is possible to increase the three elements of the tone, the frequency of the fundamental wave decided the pitch, with respect to the fundamental wave and the wave height of the harmonics determine the volume, of the harmonics to the fundamental The waveform is determined by the ratio of the wave height and the relative phase angle, and the waveform determines the timbre.

  How the pitch, volume, and timbre, which are the components of these sounds, change as they pass through an audio device is a very important characteristic of the audio device.

  Among them, changes in pitch and volume passing through the audio equipment can be measured and quantified relatively easily. On the other hand, it is extremely difficult to quantitatively measure the change in timbre, which has made it difficult to analyze and evaluate the characteristics of audio equipment.

  Now, the timbre is determined by the waveform of the sound, and the waveform is determined by the ratio of the crest ratio of the harmonic to the fundamental wave and the relative phase angle. Can be quantitatively represented by the harmonic noise intensity generated in the above and the change in the relative phase angle in the audio equipment.

  Focusing on the wave height ratio between the fundamental wave and the harmonic wave, the change rate of the wave height ratio passing through the audio equipment is expressed by (Equation 1), (Equation 2), and (Equation 3). be equivalent to. Therefore, it can be said that the frequency characteristics of the amplification factor in the audio equipment quantitatively represent a part of the timbre characteristics of the audio equipment.

Let the peak height ratio of the fundamental wave and the harmonic at the input of the acoustic equipment be P. Let the height of the fundamental wave be H. Let the height of the harmonic wave be h. Let M be the amplification factor of the harmonic, and let M be the amplification factor of the harmonic.

  If attention is paid to harmonic noise, it can be said that the frequency characteristics of the harmonic noise of the fundamental wave passing through the audio device quantitatively represent a part of the timbre characteristics of the audio device.

  Here, attention is paid to the relative phase angle. The relative phase angle mentioned here is the phase angle of the harmonic when the phase angle of the fundamental wave is 0 degree. Since the frequency of the harmonic is an integral multiple of the fundamental, the angular velocity of the harmonic is also an integral multiple of the angular velocity of the fundamental.

  Here, assuming that the time at which the fundamental wave rotates from 0 degree to 360 degrees and returns to 0 degree again is T, at the same time T, the harmonics rotate by an integral multiple of 360 degrees and become the original phase angle. , The relative phase angle is always constant.

  However, in general, the transmission delay time of an acoustic signal in an audio device is not constant depending on the frequency, and the apparent elapsed time of the signal is the real time plus the transmission delay time. For this reason, when the fundamental wave rotates 360 degrees in T time, the harmonic changes by the difference t time between the transmission delay time of the fundamental wave and the transmission delay time of the harmonic, and becomes t times the angular velocity of the harmonic. The relative phase angle will change. Therefore, since the frequency characteristic of the transmission delay in the audio device causes a change in the relative phase angle, it can be regarded as a part of the timbre characteristic of the audio device together with the frequency characteristic of the amplification factor.

  Actually, there are some problems in quantifying the timbre characteristics of an audio device with the frequency characteristics of these three factors, that is, amplification factor, harmonic noise, and transmission delay in the audio device. That is, the numerical values of the amplification factor, harmonic noise, and transmission delay do not appear as changes in timbre as they are, but changes in relative values to the fundamental wave appear as changes in timbre.

Only by obtaining these relative values can the timbre characteristics be directly and quantitatively evaluated. Therefore, a temporary fundamental wave is determined, and in that case, the relative values of the amplification factor, harmonic noise, and transmission delay are calculated, and this value is used as the characteristic value of the audio device. However, if the transmission delay is represented by time, it is difficult to realize how much the actual delay has an effect on the actual wave. Therefore, the time is represented by an angle as the phase angle of the temporary fundamental wave.

  Assuming that the frequency of the provisional fundamental wave is F, the frequency characteristic of P obtained from (Equation 4) is “FHz relative amplification factor”, and the frequency characteristic of Q obtained from (Equation 5) is “FHz relative harmonic noise”. , (Equation 6) and the frequency characteristic of θ obtained from (Equation 7) are referred to as “FHz relative phase angle”.

The frequency at which “FHz relative amplification factor”, “FHz relative harmonic noise”, and “FHz relative phase angle” are determined is f. The amplification factor of frequency f is m. The “FHz relative amplification factor” of frequency f is P. Let n be the harmonic noise of the frequency f Let Q be the “FHz relative harmonic noise” of the frequency f Let t be the transmission delay time of the frequency f Let θ be the “FHz relative phase angle” of the frequency f Let the frequency of the wave be F Let the amplification factor of the frequency F be M Let the wave height of the frequency F be N Let the transmission delay time of the frequency F be T Let the angular velocity of the frequency F be ω

  In the world of sound, since the sound of 440 Hz (Sound A) is often used as a reference, the relative values of the amplification factor, harmonic noise ratio, and transmission delay when the fundamental wave is set to 440 Hz are measured here. This value is used as the characteristic value of the audio equipment. However, if the transmission delay is expressed in terms of time, it is difficult to realize how much the actual wave is affected. Therefore, the time is expressed as an angle as a phase angle at 440 Hz. Thereafter, these values are referred to as “A sound relative amplification factor”, “A sound relative harmonic noise”, and “A sound relative phase angle”, respectively.

Here the actual measuring method, receives the analog sine wave of a frequency of interest to the acoustic equipment to be measured, respectively determine the height and phase by simultaneously digitized complex Fourier transform both the signal output section and the input section From the difference between the input value and the output value, the amplification factor, harmonic noise, and delay time when passing through the audio equipment are measured. This measurement is performed at each frequency, and the converted value of the relative value with respect to the reference frequency is displayed as a characteristic value in the form of a frequency characteristic graph or the like with the horizontal axis representing the frequency.

  By expressing the timbre characteristics of audio equipment as "A-sound relative amplification factor", "A-sound relative harmonic noise", and "A-sound relative phase angle", the timbre characteristics that were conventionally subjective evaluations can be quantitatively and objectively evaluated. It can be evaluated.

FIG. 1 is an explanatory diagram showing a method for implementing an audio analyzer.

  FIG. 1 shows an embodiment of the apparatus of the present invention, and is a conceptual diagram in the case of measuring the characteristics of a shielded cable used for connecting between an electric guitar and a guitar amplifier.

In FIG. 1, reference numeral 2 denotes a shielded cable to be measured.
No. 1 is inserted assuming a practical use since the output impedance of an electric guitar is usually about 100 KΩ, which is a resistance of 100 KΩ.
Reference numeral 3 denotes a resistor of 1 MΩ, and the input impedance of the guitar amplifier is usually about 1 MΩ.

4, a digital-to-analog converter (hereinafter, DAC hereinafter) is to receive the discrete sine wave (digital sine wave) to generate a sine wave (analog sine wave).
5, an input unit analog-to-digital converter (hereinafter, the input unit ADC hereinafter) is to output the voltage to be measured shielded cable input unit discrete turned into digital data.
6, the output unit analog-to-digital converter (hereinafter, an output unit ADC notation), and outputs a voltage of a measured shielded cable output unit discrete turned into digital data.

7 is a plurality of discrete sinusoidal this discretization sine wave having the same phase generator for generating a (i.e., synchronization) and a plurality of discrete cosine wave and supplies the discretized sine wave DAC, an input Fourier transform unit both discrete cosine wave and discrete sine wave, and supplies to the output Fourier transform unit.

8, the input is the Fourier transform unit calculates the input discrete complex Fourier transform by discrete cosine wave and digital data from the input ADC and discrete sine wave Ru prompted portion Fourier coefficients.
9, the output is the Fourier transform unit calculates the output discrete complex Fourier transform by discrete cosine wave and digital data from the output ADC discretization sinusoidal, Ru obtains an output unit Fourier coefficients.

Reference numeral 10 denotes a display unit for calculation processing and the result thereof. The calculation unit 10 calculates “A sound relative amplification factor” and “A” based on the Fourier transform values (the input unit Fourier coefficient and the output unit Fourier coefficient) obtained from the input / output Fourier transform unit. Sound relative harmonic noise and “Sound relative phase angle” are obtained and displayed.

  (Table 1), (Table 2), and (Table 3) show the results of actual measurement of data A, data B, and data C.

  (Table 4) is a graph of the relative amplification factor of the A sound in (Table 1). From this graph, it can be seen that the material B does not change the timbre due to the change in the amplification factor. Material A has the largest change in timbre due to a change in amplification factor, and material C is intermediate between A and B.

(Table 5) is a graph of the relative phase angle of the A sound in (Table 2).
From this graph, it can be seen that the material B does not change the timbre due to the change in the relative phase angle. Material A has the largest change in timbre. Material C is intermediate between A and B.

  From Table 3, it can be seen that "Sound A relative harmonic noise" is at an extremely low level and has no significant effect on the timbre.

  From the above results, it can be seen that the material B does not change the timbre most. Material A has the largest change in timbre. Material C is intermediate between A and B.

REFERENCE SIGNS LIST 1 100 KΩ resistor 2 Shielded cable under test 3 1 MΩ resistor 4 Digital-to-analog converter 5 Input analog-to-digital converter 6 Output analog-to-digital converter 7 Discretized sine and cosine wave generator 8 Input discrete complex Fourier transform Calculation unit 9 Output discretized complex Fourier transform calculation unit 10 Operation processing and result display unit

Claims (4)

Generating means for generating digital sine waves and digital cosine waves of a plurality of frequencies and synchronized with each other;
Digital-to-analog conversion means for generating an analog sine wave based on the digital sine wave,
Means for inputting the analog sine wave to the acoustic device to be measured,
Analog-to-digital conversion means for converting analog signals of the input unit and the output unit of the audio device under test to digital data, respectively.
Fourier transform means for performing a Fourier transform based on the digital sine wave and digital cosine wave and the input part digital data and the output part digital data,
The wave height of the analog sine wave between the input unit and the output unit in the audio device under test for each of the plurality of frequencies based on the input unit Fourier coefficient and the output unit Fourier coefficient obtained by the Fourier transform unit. Between the input unit and the output unit in the audio device under measurement for each of the plurality of frequencies, based on the input unit Fourier coefficient and the output unit Fourier coefficient obtained by the Fourier transform means . A transmission delay time of the analog sine wave is obtained , and further based on a ratio of a peak height and a transmission delay time of the analog sine wave obtained for each of the plurality of frequencies, a gain frequency characteristic and a transmission delay time frequency characteristic are determined. Calculating means for calculating a relative amplification factor and a relative phase angle based on a sine wave having a frequency of
An audio equipment timbre characteristic evaluation device comprising: The predetermined frequency is audio equipment tonal characteristic evaluation apparatus according to claim 1 Ru 440Hz der. Generating digital sine and digital cosine waves of a plurality of frequencies and synchronized with each other;
A digital-to-analog conversion step of generating an analog sine wave based on the digital sine wave,
A step of inputting the analog sine wave to the acoustic device to be measured,
A digital-to-analog conversion step of converting analog signals of the input unit and the output unit of the audio device under test into digital data, respectively.
A Fourier transform step of performing a Fourier transform based on the digital sine wave and digital cosine wave and the input section digital data and the output section digital data,
The height of the analog sine wave between the input unit and the output unit in the audio device under test for each of the plurality of frequencies based on the input unit Fourier coefficient and the output unit Fourier coefficient obtained in the Fourier transform step. Between the input unit and the output unit in the audio device under measurement for each of the plurality of frequencies, based on the input unit Fourier coefficient and the output unit Fourier coefficient obtained in the Fourier transform step . A transmission delay time of the analog sine wave is obtained , and further based on a ratio of a peak height and a transmission delay time of the analog sine wave obtained for each of the plurality of frequencies, a gain frequency characteristic and a transmission delay time frequency characteristic are determined. a calculation step of calculating the relative gain and relative phase angle of the reference sine wave of a frequency of,
A method for evaluating the timbre characteristics of audio equipment provided with: Audio equipment tonal characteristic evaluation method according to claim 3 wherein the predetermined frequency is Ru 440Hz der.