JPH02109500A - Frequency characteristic measuring instrument for speaker - Google Patents

Abstract

PURPOSE:To measure a large input quickly by applying inverse Fourier transform to an object spectrum required for the measurement, giving a time function signal to a speaker, applying Fourier transform to an electric signal from a microphone so as to obtain a response spectrum. CONSTITUTION:An object spectrum generating means 2 generates a spectrum required for the measurement such as a spectrum whose low frequency is cut off. The object spectrum is received by an inverse Fourier transform means 4, which generates a time function signal having the object spectrum. In this case, the time function is given to the speaker 6. The output sound from the speaker 6 is converted into an electric signal by a microphone 8. A Fourier transform means 10 analyzes the electric signal into the frequency spectrum and an output means 12 displays it. Thus, the measurement is implemented quickly to measure a large input.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a device for measuring the frequency characteristics of a speaker.

[Prior Art] Conventionally, when measuring the frequency characteristics of a speaker, the output of a beat frequency oscillator is given to the speaker, the output sound of the speaker is picked up by a microphone, and the sound is recorded by a level recorder. That is, the measurement is performed by changing the oscillation frequency of the B-i frequency oscillator.

[Problems to be Solved by the Invention] However, in such conventional measurements, since the speed of the level recorder is slow, the oscillation frequency of the oscillator must be changed slowly accordingly. For this reason, the time during which the signal is applied becomes long, and when measuring a large input, there are problems such as the speaker coil being burnt out.

This is particularly noticeable in high-frequency speakers (toitors), and it is extremely difficult to perform measurements using more than IOW of human power with toitors.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above problems and provide a frequency characteristic measuring device that can quickly measure large inputs.

[Means for Solving the Problems] The overall configuration of a measuring device according to a first aspect of the present invention is shown in FIG. This measuring device includes a target spectrum generating means 2, an inverse Fourier transform means 4 that generates a time function signal having a target spectrum, a speaker 6, a microphone 8 that converts the output sound from the speaker 6 into an electrical signal, and a frequency spectrum of the electrical signal. 10. Fourier transform means for analyzing and obtaining a response spectrum. It is equipped with an output means 12 for displaying the response spectrum.

FIG. 2 shows the overall configuration of a measuring device according to a second aspect of the present invention. This measuring device includes signal generating means 50 for generating a frequency sweep signal. Filter means 5 that does not pass a predetermined frequency band
2. A speaker 6 that receives the output of the filter means 52, a microphone 8 that converts the output sound from the speaker 6 into an electrical signal, a Fourier transform means 10 that analyzes the electrical signal into a frequency spectrum and obtains a response spectrum, and an output that displays the response spectrum. Means 12 are provided.

[Operation] In FIG. 1, the target spectrum generating means 2 generates a spectrum necessary for measurement, for example, a spectrum with the low frequency cut off. In response to this target spectrum, the inverse Fourier transform means 4 generates a time function signal having the target spectrum. This time function signal is given to the speaker 6. The sound output from the speaker 6 is converted into an electrical signal by the microphone 8. Fourier transform means
O analyzes this electrical signal into a frequency spectrum, and output means 12 displays it.

Further, in FIG. 2, the signal generating means 50 generates a frequency swept signal. The filter means 52 receives the output from the signal generation means 50 and does not allow components in a predetermined frequency band (eg, low frequency range) to pass through.

[Embodiment] FIG. 3 shows the hardware configuration of a measuring device according to an embodiment of the present invention. The CPU 22 performs calculations and controls each device according to a program stored in the ROM 20. The program stored in the ROM 20 is shown in a flowchart in FIG.

First, in step S, the maximum measurement input MAX to be applied to the speaker 6 is input using the keyboard 42. Next, in step S, a measurement range is input. In this example, ■2000Hz~20KH25■2
3 of 0Hz ~ 20KHz, ■20Hz ~ 20KHz
Two measurement ranges are available. The selected measurement range, ie, the target spectrum, is displayed on the CRT 32 (step S). The CPU 22 performs inverse Fourier transform and calculates a signal waveform having this target spectrum. In this embodiment, a sine wave signal waveform is calculated. The CPU 22 calculates this signal waveform in the form of digital data and stores it in the RAM 24.

In this embodiment, 1024 points of data are stored.

Next, provisional measurements are performed based on this waveform data (step SS). The provisional measurement is performed to determine the attenuator level of the fast Fourier transformer 38, which is the Fourier transform means. Temporary measurements are made at the IW level.

After the preliminary measurement, perform the actual measurement. Digital waveform data stored in RAM 24 is converted into an analog waveform in D/A converter 26. This output waveform is given to the speaker 6 via the amplifier 28. First, the measurement maximum input MAX input in step S
The gain of the amplifier 28 is adjusted by the CPU 22 so that the signal is given to the speaker 6.

The output sound from speaker 6 is from microphone 8 and microphone amplifier 3.
4 to an A/D converter 36, where it is converted into a digital signal. This digital signal is processed by FFT3
8, the response spectrum is calculated. The CPU 22 causes the CRT 32, which is an output means, to display this response spectrum (step St).

Next, lower the level by 3 dB and repeat the same measurement eight times.

Finally, the response spectrum at each level is output from the printer 30, which is an output means. 2000Hz~20
The measurement results at KHz are shown in FIG.

In this example, 20m for measurements from 2000Hz to 20KHz.20m for measurements from 200Hz to 20KHz.
00m5.2000m with measurement of 20Hz ~ 20KHz
It can be done in 5. Therefore, it is also possible to measure frequency characteristics with an input of 100 W or more.

Note that in other embodiments, a swept sine wave (Swept sine wave) having a frequency component of 20 Hz to 20 KHz is used.
in wave) is stored in the RAM 24 as digital data, and the CPU 22 calculates the
Frequency components of 200 Hz or 20 to 2000 Hz may be removed.

Furthermore, in the embodiments described above, the functions shown in FIGS. 1 and 2 are realized by software using a microprocessor, but they may also be implemented only by hardware such as logic circuits.

[Effects of the Invention] The measuring apparatus according to claims 1 and 2 obtains a response spectrum using a Fourier transform means, and therefore can perform measurements more quickly than conventional apparatuses. Therefore, a measuring device capable of measuring large inputs can be provided.

Further, since the band is limited by the target spectrum or the filter means, unnecessary spectral components are not applied to the speaker, and accurate measurement can be performed.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the overall configuration of a measuring device according to claim 1,
FIG. 2 is a diagram showing the overall configuration of a measuring device according to claim 2,
FIG. 3 is a diagram showing the hardware configuration of a measuring device according to an embodiment, FIG. 4 is a flowchart of a program stored in the ROM 20, and FIG. 5 is a diagram showing a measured response spectrum. 2...Objective spectrum generating means 4...Inverse Fourier transform means 6...Speaker 8...Microphone 10...Fourier transform means 12...Output means 50...Signal generating means 52... Filter means Fig. 1 Z Filter means Fig. 2 Fig.

Claims (2)

[Claims] (1) Target spectrum generating means for generating the target spectrum required for measurement; Inverse Fourier transform means for generating a time function signal having the target spectrum based on the target spectrum and applying it to the speaker; and converting the output sound from the speaker into an electrical signal. A frequency characteristic measuring device comprising: a microphone that converts an electrical signal into a frequency spectrum; a Fourier transform means that analyzes an electrical signal into a frequency spectrum and obtains a response spectrum; and an output means that displays a response spectrum. (2) Signal generation means that generates a frequency sweep signal, filter means that is connected to the output of the signal generation means and does not allow a predetermined frequency band to pass through, a speaker that receives the output of the filter means, and converts the output sound from the speaker into an electrical signal. A frequency characteristic measuring device characterized by comprising: a microphone that analyzes an electrical signal into a frequency spectrum, a Fourier transform means for obtaining a response spectrum by analyzing the electric signal, and an output means for displaying the response spectrum.