WO2020158195A1

WO2020158195A1 - Speaker minimum resonance frequency measurement device, speaker system, and speaker minimum resonance frequency measurement method

Info

Publication number: WO2020158195A1
Application number: PCT/JP2019/048212
Authority: WO
Inventors: 中村　真巳
Original assignee: 株式会社Ｊｖｃケンウッド
Priority date: 2019-01-28
Filing date: 2019-12-10
Publication date: 2020-08-06
Also published as: JPWO2020158195A1; JP7024890B2

Abstract

A sine wave output unit 2 (audio output unit) outputs an audio signal of a certain frequency to a speaker (10). A sound pickup unit (3) picks up audio outputted from the speaker (10). A signal output control unit (41) controls the frequency of audio signal to be outputted by the speaker (10) and the presence/absence of signal output. A frequency measurement unit (43) measures the frequency of the audio picked up by the sound pickup unit (3) after cessation of the audio signal that is outputted to the speaker (10). A determination unit (44) determines that the frequency of the audio signal is higher than the minimum resonance frequency of the speaker (10) when the measured frequency is lower than the frequency of the audio signal.

Description

Speaker minimum resonance frequency measuring device, speaker system, and speaker minimum resonance frequency measuring method

The present disclosure relates to a speaker minimum resonance frequency measuring device, a speaker system, and a speaker minimum resonance frequency measuring method.

Generally speaking, a speaker is composed of a voice coil, a diaphragm, a speaker unit including a magnet, and an enclosure for fixing the speaker unit. Alternatively, the speaker unit may be attached to a vehicle door or the like and the space inside the door may be used as an enclosure.

 The speaker has a limit in the frequency that can be faithfully reproduced, and if a signal with a frequency exceeding the limit is output, the sound quality deteriorates. For example, when an audio signal having a frequency equal to or lower than the lowest resonance frequency f0 of the speaker is output, although a magnetic flux is generated in the voice coil and the diaphragm tries to vibrate, the low frequency cannot be followed and the reproduced sound is distorted. Or noise is generated.

In view of this, by providing a filter for cutting a signal of a frequency equal to or lower than the minimum resonance frequency f0 in an amplifier inside or outside a speaker, it is possible to prevent distortion of reproduced sound or noise and reproduce an audio signal with high accuracy. You can

JP, 2005-341534, A

The minimum resonance frequency f0 of the speaker depends on the characteristics of the speaker unit, the size of the enclosure, the presence or absence of baffles, and the installation environment. Therefore, even if the value of the lowest resonance frequency f0 is specified as a specification for the speaker unit in advance, the characteristics may not meet the specifications. If the cutoff frequency of the filter in the front stage of the speaker is set in accordance with the lowest resonance frequency f0 defined by the speaker unit, a frequency equal to or lower than the lowest resonance frequency f0 of the speaker in the installation environment may be input to the speaker. Then, vibration that is unnecessary for the speaker is generated, which causes distortion or noise of the reproduced sound described above.

Embodiments provide a speaker minimum resonance frequency measuring device, a speaker system, and a speaker minimum resonance frequency measuring method capable of accurately measuring the speaker minimum resonance frequency and suppressing unnecessary vibration of the speaker. With the goal.

According to the first aspect of the embodiment, with respect to the audio output unit that outputs the audio signal of the predetermined frequency to the speaker, the sound collecting unit that collects the audio output from the speaker, and the audio output unit, After the output of the audio signal is stopped by the control of the signal output control unit and the signal output control unit that controls the frequency of the audio signal and the presence or absence of signal output, the frequency of the audio collected by the sound collection unit is set. The minimum resonance of the speaker, which includes a frequency measuring unit for measuring and a determination unit that determines that the frequency of the audio signal is higher than the minimum resonance frequency of the speaker when the measured frequency is lower than the frequency of the audio signal. A frequency measuring device is provided.

According to a second aspect of the embodiment, there is provided a speaker system including the above-described minimum resonance frequency measuring device for a speaker, the speaker, and a filter having a cutoff frequency that is the minimum resonance frequency of the measured speaker. It

According to the third aspect of the embodiment, the audio output unit outputs the audio signal of the predetermined frequency to the speaker and then stops the output, and after the output of the audio signal is stopped, the sound collecting unit outputs the audio signal to the speaker. The sound output from the sound is collected, the frequency of the sound collected by the sound collecting unit is measured, and when the measured frequency is lower than the frequency of the sound signal, the frequency of the sound signal is the lowest of the speaker. A method for measuring the minimum resonance frequency of a speaker that is determined to be higher than the resonance frequency is provided.

According to the speaker minimum resonance frequency measuring device, the speaker system, and the speaker minimum resonance frequency measuring method of the embodiment, it is possible to accurately measure the minimum resonance frequency of the speaker and suppress unnecessary vibration of the speaker.

FIG. 1 is a block diagram showing a minimum resonance frequency measuring device for a speaker according to an embodiment. FIG. 2 is a sequence diagram showing an operation of the lowest resonance frequency measuring device for a speaker according to an embodiment. FIG. 3 is a waveform showing the waveform of the output signal and the waveform of the sound picked up by the sound pickup unit when the sine wave sound signal of 30 Hz is output and stopped in the speaker minimum resonance frequency measuring device according to the embodiment. It is a figure. FIG. 4 is a waveform diagram showing waveforms of the output signal and the sound collected by the sound collecting unit when the sine wave sound signal of 20 Hz is output and stopped in the speaker minimum resonance frequency measuring device according to the embodiment. is there. FIG. 5 is a configuration diagram of a speaker system according to an embodiment.

<Configuration of Minimum Resonance Frequency Measuring Device for Speaker According to One Embodiment>
With reference to FIG. 1, a configuration of a minimum resonance frequency measuring device for a speaker (hereinafter, f0 measuring device) according to an embodiment will be described. The f0 measuring apparatus 1 according to the present embodiment measures the lowest resonance frequency f0 of the speaker 10 to be processed, and includes a sine wave output unit 2 as a sound output unit, a sound pickup unit 3, and a measurement unit 4. Equipped with.

The sine wave output unit 2 outputs a sine wave audio signal having a predetermined frequency to the speaker 10. The sine wave output unit 2 is specified by, for example, storing sine wave audio signals having a plurality of frequencies in a storage unit such as a ROM (Read Only Memory) and a CPU (Central Processing Unit) executing a computer program. Outputs audio signal of frequency. The sine wave output unit 2 may generate and output an audio signal of a specified frequency by hardware such as FPGA (Field Programmable Gate Array) or ASIC (Application Specific Integrated Circuit).

The speaker 10 has a magnet 11, a voice coil 12, a magnet 11, a voice coil 12 wound around a voice coil bobbin (not shown), and a diaphragm 13. By supplying a predetermined amount of current to the voice coil 12 based on the audio signal output to the speaker 10, the air in the speaker 10 is compressed or expanded to become a kind of air spring, and the vibration of this air spring causes a specific frequency Causes the diaphragm 13 to resonate, and outputs a voice corresponding to the voice signal. The sound pickup unit 3 picks up the sound output from the speaker 10. Typically, the sound pickup unit 3 is a microphone.

The measurement unit 4 includes a signal output control unit 41, a sound collection information acquisition unit 42, a frequency measurement unit 43, a determination unit 44, and an f0 measurement unit 45 as a minimum resonance frequency measurement unit. The signal output control unit 41 controls the frequency of the audio signal output from the speaker 10 and the presence/absence of signal output to the sine wave output unit 2. The sound collection information acquisition unit 42 acquires the sound information collected by the sound collection unit 3. The frequency measuring unit 43 measures the frequency of the sound collected by the sound collecting unit 3 after the sine wave output unit 2 stops outputting each sound signal to the speaker 10 according to an instruction from the signal output control unit 41.

The measuring unit 4 can realize the functions described above by the CPU executing the computer program. The measurement unit 4 may realize the above-described functions by hardware such as FPGA or ASIC.

The determination unit 44 determines that the frequency obtained by the measurement process of the frequency measurement unit 43 is a predetermined value higher than the frequency of the audio signal output from the sine wave output unit 2 to the speaker 10 before being stopped by the signal output control unit 41. When it is higher than the above, it is determined that the frequency of the corresponding audio signal is equal to or lower than the lowest resonance frequency f0. Further, when the frequency obtained by the measurement process is lower than the frequency of the corresponding audio signal, the determining unit 44 determines that the frequency of the corresponding audio signal is higher than the lowest resonance frequency f0.

If the frequency of the audio signal and the frequency obtained by the frequency measuring unit 43 are the same, the f0 measuring unit 45 sets the frequency as the lowest resonance frequency f0 of the speaker 10.

<Operation of Minimum Resonance Frequency Measuring Device for Speaker According to One Embodiment>
Next, with reference to the sequence diagram of FIG. 2, the operation when the lowest resonance frequency f0 of the speaker 10 is measured using the f0 measuring device 1 will be described. First, the signal output control unit 41 of the measurement unit 4 sends to the sine wave output unit 2 an instruction to output an audio signal having a preset frequency (for example, 30 Hz) for a predetermined time (for example, 1 second) (S1). As the frequency instructed here, for example, a value predicted to be close to the lowest resonance frequency f0 of the speaker 10 is used. Then, the sine wave output unit 2 outputs the sine wave audio signal having the frequency instructed by the measurement unit 4 to the speaker 10 (S2). When a sine wave audio signal is output to the speaker 10, a predetermined amount of current flows in the voice coil 12 based on the sine wave audio signal, causing vibration in the air inside the speaker 10 and causing the diaphragm 13 to resonate. , And the corresponding voice is output (S3).

After the output processing of the sine wave audio signal in the sine wave output unit 2 is started, when the time instructed by the measurement unit 4 has elapsed (“YES” in S4), the output of the sine wave audio signal is stopped (S5). ). When the output of the sine wave audio signal is stopped here, no current flows in the voice coil 12 in the speaker 10. Here, even after the current stops flowing, the resonance of the diaphragm 13 in the speaker 10 continues due to inertia and gradually attenuates. Therefore, immediately after the sine wave audio signal is stopped, the audio having the same level of frequency as when the signal was being output is output. At this time, the resonance of the diaphragm 13 gradually attenuates and approaches the lowest resonance frequency f0 of the speaker 10. In other words, the frequency of the sound output from the speaker 10 after the output of the sine wave audio signal is stopped changes from the frequency of the sine wave audio signal to the lowest resonance frequency f0.

The sound output from the speaker 10 after the sine wave sound signal is stopped is collected by the sound collecting unit 3, and the sound information is transmitted to the measuring unit 4 (S6). In the measuring section 4, the sound information transmitted from the sound collecting section 3 is acquired by the sound collecting information acquiring section 42 (S7), and the frequency is measured by the frequency measuring section 43 (S8).

Then, in the determination unit 44, the frequency obtained by the measurement processing in the frequency measurement unit 43 is the sine wave audio signal output from the sine wave output unit 2 to the speaker 10 before being stopped by the signal output control unit 41. It is determined whether the frequency is lower than the frequency of (S9).

For example, as shown in FIG. 3A, the sine wave output unit 2 outputs a 30 Hz sine wave audio signal to the speaker 10 according to an instruction from the signal output control unit 41, and outputs the sine wave audio signal after a predetermined time has elapsed. To stop. At this time, as shown in FIG. 3B, the sound pickup unit 3 picks up the voice output by inertia even after the output of the sine wave voice signal is stopped.

Here, the frequency fB obtained by the measurement process in the frequency measuring unit 43 after the signal is stopped is lower than the frequency fA of the sine wave audio signal output from the sine wave output unit 2 to the speaker 10, for example, 25 Hz. Suppose In this case, the determination unit 44 determines that the frequency 30 Hz of the sine wave audio signal is higher than the lowest resonance frequency f0 (S10). In other words, the predicted f0 value of the speaker 10 is determined to be lower than 30 Hz. Although the frequency of the output of the speaker 10 immediately after the signal is stopped is measured in FIG. 3B, the measurement is not limited to immediately after the signal is stopped. Since the output of the speaker 10 approaches the lowest resonance frequency f0 while gradually attenuating, it is preferable that a long time has elapsed from the signal stop in the period in which the measurable output level is output from the speaker 10.

Next, the user who recognizes the result that the f0 predicted value of the speaker 10 is lower than 30 Hz by the f0 measuring unit 45 operates the measuring unit 4 and outputs a sound signal of a frequency lower than 30 Hz, for example, 20 Hz. Let The measurement unit 4 transmits to the sine wave output unit 2 an instruction to output a 20 Hz audio signal for a predetermined time (for example, 1 second) based on a user operation. The measurement unit 4, the sine wave output unit 2, the speaker 10, and the sound collection unit 3 perform the same processing as steps S1 to S10 described above.

Similar to FIG. 3A, as shown in FIG. 4A, the sine wave output unit 2 outputs a 20 Hz sine wave audio signal to the speaker 10 according to an instruction from the signal output control unit 41, and after a predetermined time elapses. Stop outputting the sine wave audio signal.

As shown in FIG. 4B, the frequency fD obtained by the measurement process in the frequency measuring unit 43 after the output of the sine wave audio signal is stopped at this time is more than 20 Hz which is the frequency fC of the sine wave audio signal. When it is high, it is determined that the lowest resonance frequency f0 of the speaker 10 is higher than 20 Hz. As a result, the f0 measuring unit 45 measures the predicted f0 value of the speaker 10 to be 20 Hz or higher. Then, in the f0 measuring unit 45, the f0 predicted value of the speaker 10 is further measured as 20 Hz or more and less than 30 Hz based on the two predicted values measured in the above-described processing. Although the frequency of the output of the speaker 10 immediately after the signal is stopped is measured in FIG. 4B, the measurement is not limited to immediately after the signal is stopped.

At this time, since the voice having the lowest resonance frequency f0 or less of the speaker 10 is input to the speaker 10, the speaker 10 cannot follow the low frequency, which causes unnecessary vibration, which may cause distortion or noise. May be. Therefore, it is not preferable to use the voice having the lowest resonance frequency f0 or less as the voice signal. It is practically preferable that the frequency of the audio signal be gradually set low, for example, by 3 Hz so that the measured frequency fD does not become lower than the minimum resonance frequency f0.

According to the above-described embodiment, a highly accurate f0 predicted value can be measured by a simple process using a voice generated by inertia after the output of the voice signal to the speaker 10 is stopped. When the speaker unit alone is measured, the f0 predicted value as the characteristic of the speaker unit can be measured, and when the speaker 10 is mounted in an enclosure or the like, the f0 predicted value of the system including the enclosure can be measured. By disposing a filter for cutting a signal having a frequency equal to or lower than the measured f0 predicted value, that is, a filter having a cutoff frequency of the lowest resonance frequency f0 of the measured speaker 10, distortion of reproduced sound or It is possible to configure the high-performance speaker 10 in which the generation of noise is prevented with high accuracy.

It is preferable that the above-described filter that cuts the signal having the frequency equal to or lower than the f0 predicted value is an adaptive filter in which the frequency that is the measured f0 predicted value is automatically set as the cutoff frequency. Alternatively, it may be set in step 1. Further, the location of the filter that cuts the signal of the frequency equal to or lower than the f0 predicted value is not limited to the inside of the speaker 10, and may be provided in an external amplifier. You may be asked.

　Especially, in the case of in-vehicle speakers, a speaker box is installed on the door and the minimum resonance frequency f0 changes depending on the shape or size of the vehicle. By providing a filter for cutting a signal of a frequency equal to or lower than the f0 predicted value measured by the f0 measuring device 1 for each vehicle, an optimum reproduction environment can be provided for any vehicle.

Further, the user who has recognized the f0 predicted value measured by the above-described processing repeats the above-described processing of steps S1 to S10 using the sine wave audio signal of 20 Hz or more and less than 30 Hz, so that the speaker 10 with higher accuracy The f0 predicted value can be measured.

As another embodiment, even if the signal output control unit 41 of the measurement unit 4 is set with a plurality of different frequencies including a frequency higher and a frequency lower than the lowest resonance frequency f0 acquired as the specifications of the speaker 10 in advance. Good. The f0 measuring apparatus 1 sequentially executes the processes of steps S1 to S9 using the sine wave audio signals of the respective frequencies, and the measuring section 45 determines that the resonance frequency is the lowest resonance frequency f0 or less based on the determination result. The predicted maximum value of the frequency of the audio signal may be measured as the f0 predicted value of the speaker 10.

In this way, by automatically causing the measuring unit 4 to perform the measurement processing of the f0 predicted value using the sine wave audio signals of a plurality of frequencies, the f0 predicted value can be measured efficiently with high accuracy by a simple operation. be able to.

In addition, as another embodiment, the signal output control unit 41 of the measurement unit 4 obtains the frequency obtained by the measurement process of the frequency measurement unit 43 when the sine wave audio signal of the predetermined frequency is output and stopped, and The frequency of the sine wave audio signal to be output next may be determined based on the difference from the frequency of the output sine wave audio signal. With this, the f0 measuring device 1 may sequentially execute the measurement process of the f0 predicted value using a plurality of sinusoidal audio signals having different frequencies.

Specifically, the signal output control unit 41 determines that the frequency obtained by the measurement process of the frequency measurement unit 43 is higher than the frequency of the output sine wave audio signal according to the determination result of the determination unit 44, The frequency of the sine wave audio signal to be output is determined to be a low value. The f0 measuring device 1 efficiently outputs the audio signal of the determined frequency to the speaker 10 again from the sine wave output unit 2 and performs the f0 predicted value measurement process a plurality of times, thereby efficiently measuring the f0 predicted value with high accuracy. can do.

As shown in FIG. 5, the speaker system includes the above-described f0 measuring device 1, the speaker 10, and the filter 5 having the measured minimum resonance frequency f0 of the speaker 10 as the cutoff frequency. At this time, it is preferable that the f0 measuring device 1 is used when measuring the lowest resonance frequency f0 and can be detached during normal use of the speaker 10. As described above, the speaker 10 may include the filter 5 or the amplifier 7 may include the filter 5.

In FIG. 5, the audio signal output from the sound source 6 is amplified by the amplifier 7 and supplied to the speaker 10 via the filter 5. Since the filter 5 cuts the signal of the frequency equal to or lower than the lowest resonance frequency f0 of the speaker 10, it is possible to prevent distortion of reproduced sound or generation of noise with high accuracy.

The disclosure of the present application is related to the subject matter described in Japanese Patent Application No. 2019-012102 filed on January 28, 2019, the entire disclosures of which are incorporated herein by reference.

Claims

An audio output unit that outputs an audio signal of a predetermined frequency to a speaker,
A sound collecting unit for collecting the sound output from the speaker,
A signal output control unit for controlling the frequency of the audio signal and the presence or absence of signal output with respect to the audio output unit;
After the output of the audio signal is stopped by the control of the signal output control unit, a frequency measuring unit that measures the frequency of the sound collected by the sound collecting unit,
When the measured frequency is lower than the frequency of the audio signal, a determination unit that determines that the frequency of the audio signal is higher than the lowest resonance frequency of the speaker,
The lowest resonance frequency measuring device for a speaker including.
When the determination unit determines that the frequency of the audio signal is higher than the lowest resonance frequency of the speaker, the signal output control unit controls to output an audio signal of a frequency lower than the audio signal to the speaker. The minimum resonance frequency measuring device for a speaker according to claim 1.
The signal output control unit, based on the difference between the frequency measured by the frequency measuring unit when outputting and stopping the audio signal and the frequency of the audio signal, the frequency of the audio signal to be output next. The lowest resonance frequency measuring device for a speaker according to claim 2, wherein
A minimum resonance frequency measuring device for a speaker according to any one of claims 1 to 3,
The speaker,
A filter having a cutoff frequency as the lowest resonance frequency of the measured speaker,
Speaker system including.
The audio output unit stops the output after outputting the audio signal of the predetermined frequency to the speaker,
After the output of the sound signal is stopped, the sound output from the speaker is collected by the sound collection unit,
The frequency of the sound collected by the sound collecting unit is measured,
A method for measuring the lowest resonance frequency of a speaker, wherein when the measured frequency is lower than the frequency of the sound signal, it is determined that the frequency of the sound signal is higher than the lowest resonance frequency of the speaker.