JP2005253001A - Crossover frequency estimation apparatus and audio apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To estimate the crossover frequency of a speaker with an extremely simple configuration. <P>SOLUTION: The sound pressure level of a speaker is measured in three frequency bands, and the crossover frequency is determined by referring to an estimation table TBL on the basis of the result of the measurements. When an average sound pressure level is 0 dB, for example, when both sound pressure levels of 120 Hz and 80 Hz are 0 dB or higher, it is estimated that the crossover frequency of the speaker is ≤80 Hz. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a crossover frequency estimation apparatus and an audio apparatus suitable for use in estimating a crossover frequency of a speaker.

  Many audio systems in recent years reproduce 5.1 channel surround sound. In this case, it is important to appropriately set the crossover frequency of the subwoofer that handles the bass region and other speakers.

  By the way, when setting the crossover frequency, generally, a setting method has been adopted in which the setting is made by referring to a specification table showing the frequency characteristics of the speaker or by actually listening with the ear. However, even if the setting is made by looking at the specification table, the frequency characteristics at the viewing position change depending on the situation of the installation location of the speaker. In addition, the method of setting by listening with the ear depends on the subjective feeling of the setter, so it is difficult to ensure accuracy.

On the other hand, if the frequency characteristic at the viewing position is analyzed on the frequency axis using FFT (Fast Fourier Transform), an appropriate crossover frequency can be set. However, this method requires a large amount of calculation and high performance signal. A processing device is required, and a large amount of memory is required (for example, Patent Document 1). Assuming that such a signal processing device is mounted on an audio device, there arises a problem that the configuration of the audio device becomes complicated and the price increases.
Japanese Patent Laid-Open No. 10-284965

  The present invention has been made in view of the above-described circumstances, and an object thereof is to provide a crossover frequency estimation device capable of estimating a crossover frequency with a simple configuration.

  Another object of the present invention is to provide an audio device that can automatically set the crossover frequency with a simple configuration.

  In order to solve the above-described problem, a measurement signal generating unit that generates measurement signals in a plurality of predetermined frequency bands, and a microphone that receives sound emitted from a speaker that is sounded by the measurement signal generated by the measurement signal generating unit And estimation means for estimating a crossover frequency based on a received signal of the microphone in each frequency band.

  According to this configuration, it is possible to estimate the speaker crossover frequency from the level of the received signal in a plurality of frequency bands.

Here, it is preferable to provide display means for displaying the crossover frequency obtained by the estimation means because various settings can be made while viewing the display.
The measurement signal generating means includes white noise generating means for generating white noise, and band limiting means for setting a band of an output signal of the white noise generating means, and the measurement results in the plurality of frequency bands are By recognizing the measurement result for the representative frequency of the band set by the band limiting means or the average value in the band, even if the sound pressure level of the frequency characteristic of the speaker fluctuates little by little, an accurate cross The over frequency can be estimated.

  In the audio device of the present invention, in order to solve the above-described problem, two or more output means for amplifying the supplied signal and supplying the amplified signal to the speaker, and measurement signals in a plurality of predetermined frequency bands A measurement signal generating means for generating the measurement signal, a measurement control means for selectively supplying the measurement signal generated by the measurement signal generating means to each output means and generating it from the speaker, and the speaker by the measurement control means A microphone that receives the measurement signal generated from the signal, an estimation unit that estimates a crossover frequency based on a reception signal level of the microphone in each frequency band, and an output band of the specified output unit Is set to a band corresponding to the crossover frequency estimated by the estimation means.

  Further, in the audio apparatus, the measurement signal generating means includes white noise generating means for generating white noise, and band limiting means for setting a band of an output signal of the white noise generating means, and the plurality of frequencies The measurement result in the band is preferably recognized as the measurement result for the representative frequency of the band set by the band limiting unit or the average value in the band.

  Furthermore, in the audio apparatus, a storage unit that stores a plurality of crossover frequencies estimated by the estimation unit, a selection unit that selects any one of the crossover frequencies stored in the storage unit, and a selection by the selection unit It is desirable to include a band preset unit that sets the band set to the specific output unit.

  According to the present invention, the crossover frequency of a speaker can be estimated with a simple configuration without using fast Fourier analysis.

Embodiments of the present invention will be described below.
First Embodiment FIG. 1 is a block diagram showing a configuration of an audio apparatus according to an embodiment of the present invention. In the figure, reference numeral 1 denotes a signal processing unit that performs various signal processing on an input signal. The signal processing unit 1 has a plurality of input terminals IN-1 to IN-n for receiving output signals (external audio output signals from a CD player, a DVD player, a TV tuner, etc.) from an external audio device. 5.1-channel surround processing is performed on the signal supplied to the terminal, and output signals for each channel are output to the output amplifiers 2FR, 2FL, 2FC, 2RR, 2RL, and 2SW. The output amplifiers 2FR, 2FL, 2FC, 2RR, 2RL, and 2SW amplify the input signals, respectively, and the front right speaker FR-SP, the front left speaker FL-SP, the front center speaker FC-SP, and the rear right speaker RR-. Supplied to SP, rear left speaker RL-SP, and subwoofer SW. In this case, the output side of the output amplifier 2SW is provided with a band limiting filter 3 that cuts the high band, and an audio signal with the high band cut is supplied to the subwoofer SW. The cut-off frequency fc of the band limiting filter 3 is set by the control unit 10. The control unit 10 includes a CPU, a memory, and the like, and controls each unit of the apparatus based on a predetermined program.

  Further, the front right speaker FR-SP, the front left speaker FL-SP, the front center speaker FC-SP, the rear right speaker RR-SP and the rear left speaker RL-SP are connected to the listener L as shown in FIG. The subwoofer SW is disposed at an arbitrary position, respectively, at the front right, the front left, the front center, the rear right, and the rear left.

Next, reference numeral 5 denotes a white noise generating unit, and the white noise generated here is supplied to the signal processing unit 1 as a measurement signal SS via the band limiting filter 6. In the signal processing unit 1, under the control of the control unit 10, the measurement signal SS is sequentially supplied to the output amplifiers 2FR, 2FL, 2FC, 2RR, and 2RL.
Here, the band limiting filter 6 functions as a band pass filter that allows a predetermined band to pass, and the pass band is set by the control unit 10. In this embodiment, a first band of 60 Hz to 100 Hz, a second band of 100 Hz to 140 Hz, and a third band of 60 Hz to 1060 Hz are set.
Next, 15 is a microphone, which is used at the position of the listener L. The sound input to the microphone 15 is supplied as an audio signal to the control unit 10 via the band limiting filter 16. The band limiting filter 16 is the same filter as the band limiting filter 6, and the same band as the band limiting filter 6 is set simultaneously by the control unit 10.

Next, the operation of this embodiment will be described. In the present embodiment, the crossover frequency for appropriately sharing the frequency band between the subwoofer SW and other speakers is automatically detected. Then, a cut-off frequency fc for cutting the high frequency side of the audio signal supplied to the subwoofer SW is set.
First, the listener L operates an operation unit (not shown) to instruct the control unit 10 to detect a crossover frequency. As a result, the control unit 10 activates the white noise generation unit 5 and sets the first band in the band limiting filters 6 and 16. Next, the signal processing unit 1 supplies the measurement signal SS to the output amplifier 2FR. As a result, white noise in a band of 60 Hz to 100 Hz is output from the speaker FR-SP. This sound is input to the microphone 15 to become an audio signal, and the audio signal is supplied to the control unit 10 via the band limiting filter 16. Here, since the first band is set in the band limiting filter 16 similarly to the band limiting filter 6, the sound in the band other than 60 Hz to 100 Hz output from the speaker FR-SP is blocked. As a result, the intensity of the signal supplied to the control unit 10 correctly reflects the sound pressure level in the band of 60 Hz to 100 Hz of the speaker FR-SP at the sound receiving point (the position of the listener L).

  Next, the control unit 10 sets the second band in the band limiting filters 6 and 16. As a result, white noise of 100 Hz to 140 Hz is output from the speaker FR-SP, and the control unit 10 measures the sound pressure level in the band of 100 Hz to 140 Hz of the speaker FR-SP at the sound receiving point. Next, the control unit 10 sets the third band in the band limiting filters 6 and 16 and performs the same measurement as described above.

  Through the above processing, the control unit 10 records the sound pressure levels in the bands of 60 Hz to 100 Hz, 100 Hz to 140 Hz, and 60 Hz to 1060 Hz. Here, in this embodiment, a sound pressure level of 60 Hz to 100 Hz is recognized as a sound pressure level of 80 Hz, a sound pressure level of 100 Hz to 140 Hz is recognized as a sound pressure level of 120 Hz, and 60 Hz to 1060 Hz is a speaker. It is recognized as the average sound pressure level. However, since the measurement range is different for 80 Hz, 120 Hz and the average sound pressure level, the sound pressure power (integration amount) is different. Therefore, a process for making these powers the same is performed in advance. This is because the frequency characteristics of the speaker fluctuate up and down with respect to the frequency as shown in FIG. 2, and if the sound pressure level is measured using a single frequency measurement signal, it will happen to be a mountain part. This is because it is not appropriate to recognize the result as the sound pressure level at that frequency. In the present embodiment, for the first and second bands, which are relatively low regions where the frequency characteristics of the speaker rise, the center frequency of the band is recognized as the measured frequency value (representative value). By doing this, the peaks and valleys of the frequency characteristics of the speakers included in the measurement band are averaged, and an appropriate value can be obtained as the sound pressure level at the measurement frequency (representative value).

  The control unit 10 compares the three sound pressure levels and performs the following processing. Since the sound pressure level measured here includes the frequency characteristics of the microphone and the system, these frequency characteristics are calculated. Process to keep flat. First, the average sound pressure level is set to 0 dB, and the relative sound pressure levels at 120 Hz and 80 Hz are determined. Here, FIG. 3 is an estimation table TBL provided in the memory of the control unit 10. As shown in this figure, the crossover frequency is associated with the sound pressure level in the measured frequency value. In the present embodiment, the crossover frequency is determined using the estimation table TBL as follows.

  If the average sound pressure level is 0 dB and the sound pressure levels at 120 Hz and 80 Hz are both 0 dB or more, it is estimated that the crossover frequency of the speaker is 80 Hz or less. In this case, in this embodiment, it is estimated as 60 Hz. Such a speaker is a speaker that can reproduce a considerably low frequency range. Further, when the average sound pressure level is 0 dB, if the sound pressure level at 120 Hz is −1.5 dB or more and the sound pressure level at 80 Hz is −3 dB or more, the crossover frequency of the speaker is estimated to be 80 Hz. To do. Similarly, when the average sound pressure level is 0 dB, if the sound pressure level at 120 Hz is −3 dB or more and the sound pressure level at 80 Hz is −6 dB or more, the crossover frequency of the speaker is estimated to be 120 Hz. To do. If the average sound pressure level is 0 dB and the sound pressure level at 120 Hz is less than −3 dB and the sound pressure level at 80 Hz is less than −6 dB, the crossover frequency of the speaker is estimated to be 120 Hz or more. In this embodiment, it is estimated to be 200 Hz.

4 and 5 show models of speaker frequency characteristics. In this frequency characteristic model, fine fluctuations in the sound pressure level (portions such as peaks and valleys) are averaged and modeled as a first-order high-pass filter.
In the characteristics shown in FIG. 4, the average sound pressure level and the sound pressure level at 120 Hz are 0 dB, and the sound pressure level at 80 Hz is −3 dB. In the case of this characteristic, the crossover frequency is estimated to be 80 Hz according to the estimation table TBL. In the characteristics shown in FIG. 5, the average sound pressure level is 0 dB, while the 120 Hz sound pressure level is less than −6 dB, and the 80 Hz sound pressure level cannot be measured. The speaker crossover frequency is estimated to be 200 Hz according to the estimation table TBL.

  The frequency characteristics of the speaker can be approximated as a first-order high-pass filter as shown in FIGS. 4 and 5, and the crossover frequency is a frequency at which the sound pressure level is −3 dB. From the point measurement result, the range of the crossover frequency of the speaker is known. In the present embodiment, an appropriate value within the range of the crossover frequency that can be taken by the loudspeaker to be measured is set in advance in the estimation table TBL based on the actual measurement or the calculated value. Since only the three measured values (relative values) and the crossover frequency are set in the estimation table TBL in this way, the amount of data to be stored is extremely small.

  Although the above estimation is performed for all speakers, there may be variations in the obtained crossover frequency due to variations in the characteristics of the speakers. In the present embodiment, the highest one of the obtained crossover frequencies is adopted, and the crossover frequency is set as the cut-off frequency fc of the band limiting filter 3. The one having the highest crossover frequency is used so that the sound range of the subwoofer SW and other speakers is not interrupted. That is, there is no fear that the sound range will be interrupted if it is matched with the crossover frequency of the speaker where the lowest sound is most difficult to be output.

  Next, the control unit 10 supplies the same value as the crossover frequency determined as described above to the band limiting filter 3 as the cut-off frequency fc. As a result, the band limiting filter 3 cuts the high frequency side based on the cutoff frequency fc. As a result, a low-frequency audio signal is reproduced from the subwoofer SW, and the band is smoothly connected to the band of other speakers.

The present invention is not limited to the above embodiment, and various modifications can be made.
First, although the number of measurement points is three in the above embodiment, the number of measurement points may be increased. If the number of measurement points is increased, a more accurate crossover frequency can be estimated. Further, even if the number of measurement points is increased, the data stored in the estimation table TBL is only numerical data, so the amount of data is extremely small.

  In the embodiment described above, the crossover frequency is measured for all speakers except the subwoofer. However, this may be representatively performed by one or two speakers. For example, only the front center speaker FC-SP or two front right speakers FR-SP and two front left speakers FL-SP may be used.

  In the above-described embodiment, a measurement signal is generated through a band-pass filter for white noise. However, if the influence of a minute change in the sound pressure level (peaks and valleys) of speaker characteristics can be ignored, measurement is performed at a single frequency. May be.

  As shown in FIG. 1, a display unit 20 such as a liquid crystal display may be provided to display the crossover frequency determined by the control unit 10. The operator may manually set the cutoff frequency by looking at the numerical value displayed on the display unit 20 without automatically controlling the cutoff frequency of the band limiting filter 3. In this case, many of the subwoofers SW have a built-in band-limiting filter in the subwoofer speaker box. Therefore, the band-limiting filter 3 is omitted and the subwoofer SW is referred to the display on the display unit 20. A band limiting filter built in the speaker box of the woofer SW can also be set. In this case, there is an advantage that the apparatus configuration can be further simplified. In the above-described embodiment, an example of an audio device has been described. However, the present invention can also be configured as a crossover frequency estimation device. That is, as shown in FIG. 6, the crossover frequency estimation device 30 is configured by the components surrounded by the one-dot chain line and the microphone 15, and the measurement signal SS output from the band limiting filter 6 is supplied to the input terminal of the audio device. And if an audio apparatus outputs the signal from any speaker and receives this with the microphone 15, the process similar to the above can be performed. In this case, the estimation result may be notified to the operator by display on the display unit 20, or may be output as measurement data.

In addition to the configuration of the above-described embodiment, as shown in FIG. 7, a memory 40 that stores the crossover frequency determined by the control unit 10 may be provided. Since the sound pressure level at the sound receiving point changes depending on the environment, the crossover frequency may change, for example, when the measurement is performed with the curtain closed and when the measurement is performed with the curtain opened. Therefore, the measured crossover frequency is stored in the memory 40 every time the environment changes. Then, a value corresponding to the environment is read from the memory 40, and the cut-off frequency fc of the band limiting filter 3 may be set according to this value.
In the example shown in FIG. 7, the crossover frequency is stored when the curtain is opened, when the curtain is closed, when the number of people is large, when the volume is low, or when the outdoors (when the audio device is a portable radio cassette). Has been. The memory 40 stores each crossover frequency in pairs with the preset number. In this case, when the user performs a predetermined operation on the operation unit (not shown), the control unit 10 reads out the crossover frequency of the desired preset number, and the cut-off frequency fc of the band limiting filter 3. Set.
Further, a configuration for inputting a word indicating the viewing environment may be added, and the word may be stored in the memory 40. In this case, the viewing environment corresponding to the selected preset number can be displayed on the display unit 20.

  The embodiment described above is an example in which the crossover frequency for the subwoofer SW and other speakers is set. However, when the speakers are divided into three or four bands, the output amplifiers are assigned to each output amplifier. It is also possible to provide the band limiting filter 3 and set the cut-off frequency fc by the same processing as described above.

  Further, the microphone 15 may be connected to any one of the input terminals IN-1 to IN-n of the audio device so that the signal processing unit 1 supplies the output signal of the microphone 15 to the band limiting filter 16. . When the audio device is a portable type such as a radio cassette player, a microphone built in the main body may be used. In this case, the sound is not received at the position of the listener L, but it is effective when the error is acceptable. In addition, the remote controller that gives various operation signals to the audio device has a built-in microphone, and transmits the microphone signal to the main body side using infrared rays or Bluetooth, thereby providing the same function as the microphone 15 of the above-described embodiment. Also good.

  In the embodiment described above, the control unit 10 estimates the crossover frequency based on the estimation table TBL. However, the mathematical expression is stored in place of the estimation table TBL, and the measurement result is substituted into this mathematical expression to store the crossover frequency. You may ask for. For example, an equation indicating a curve of a first-order high-pass filter may be stored, and a frequency giving −3 dB, that is, a crossover frequency may be obtained from the measured frequency value and the sound pressure level. It is also possible to obtain a plurality of speaker characteristic curves (stored by mathematical expressions or data) and obtain or interpolate the crossover frequency of the closest to the measured frequency and its sound pressure level.

It is a block diagram which shows the structure of this embodiment. It is a frequency characteristic figure which shows the characteristic of a general speaker. It is a figure which shows the memory content of the estimation table TBL in the same embodiment. It is a frequency characteristic figure which shows the model of the characteristic of a speaker. It is a frequency characteristic figure which shows the model of the characteristic of a speaker. It is a block diagram which shows the structure of the modification of this embodiment. It is a figure which shows the memory content of the memory 40 for memorize | storing the estimated crossover frequency.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Signal processing part (measurement control means), 2FR, 2FL, 2FC, 2RR, 2RL ... Output amplifier (output means), 2SW ... Output amplifier (specific output means), 3 ... Band Limiting filters (band setting means, band presetting means), 5... White noise generating unit (measurement signal generating means, white noise generating means), 6... Band limiting filter (measurement signal generating means, band limiting means) 10 ... Control part (estimation means, measurement control means, selection means, band preset means) 15 ... Microphone, 20 ... Display part (display means), 40 ... Memory (storage means).

Claims (6)

Measurement signal generating means for generating measurement signals in a plurality of predetermined frequency bands;
A microphone that receives sound emitted from a speaker that is sounded by the measurement signal generated by the measurement signal generating means;
A crossover frequency estimation apparatus comprising: estimation means for estimating a crossover frequency based on a reception signal of the microphone in each frequency band.   The crossover frequency estimation apparatus according to claim 1, further comprising display means for displaying the crossover frequency obtained by the estimation means.   The measurement signal generating means includes white noise generating means for generating white noise, and band limiting means for setting a band of an output signal of the white noise generating means, and the measurement results in the plurality of frequency bands are the band 3. The crossover frequency estimation apparatus according to claim 1, wherein the crossover frequency estimation apparatus is recognized as a measurement result of a representative frequency in a band set by the limiting unit or an average value in the band. Two or more output means for amplifying a supplied signal and supplying the amplified signal to a speaker;
Measurement signal generating means for generating measurement signals in a plurality of predetermined frequency bands;
Measurement control means for selectively supplying the measurement signals generated by the measurement signal generation means to the output means and generating them from the speaker;
A microphone for receiving the measurement signal generated from the speaker by the measurement control means;
Estimating means for estimating a crossover frequency based on a received signal level of the microphone in each frequency band;
Band setting means for setting the output band of the specified one of the output means to a band corresponding to the crossover frequency estimated by the estimation means;
An audio apparatus comprising:   The measurement signal generating means includes white noise generating means for generating white noise, and band limiting means for setting a band of an output signal of the white noise generating means, and the measurement results in the plurality of frequency bands are the band 5. The audio apparatus according to claim 4, wherein the audio device is recognized as a measurement result of a representative frequency in a band set by the limiting unit or an average value in the band. Storage means for storing a plurality of crossover frequencies estimated by the estimation means;
Selecting means for selecting any crossover frequency stored in the storage means;
6. The audio apparatus according to claim 4, further comprising: a band preset unit that sets a band selected by the selection unit to the specific output unit.

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