JP2012182648A - Amplifier, mobile body information apparatus, amplifier power saving method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress power consumption in an amplifier by removing a sound signal with a low frequency even when a predetermined woofer amplifier is not provided.SOLUTION: An amplifier includes: a volume adjustment part 6 for adjusting the volume of an input sound signal; a high-pass filter 5 for attenuating the low-pass frequency component of the input sound signal; a power saving control part 3 for determining whether the volume adjusted by the volume adjustment part 6 is lower than a volume threshold or not; and a signal control part 4 for outputting the input sound signal to the high-pass filter 5 when the power saving control part 3 determines that the volume adjusted by the volume adjustment part 6 is lower than the volume threshold.

Description

  The present invention relates to an amplifier, and more particularly to a technique for suppressing power consumption.

  Conventionally, audio that has a plurality of speakers that reproduce sounds from low to high frequencies and can reproduce wide-band sounds has been distributed. Such audio can reproduce music that is close to the actual sound and is clear and powerful, but on the other hand, the power consumption of amplifiers and speakers increases as broadband sound is reproduced. Are known.

  On the other hand, in the case where such an audio is provided in a moving body (for example, an automobile, etc.), depending on the volume the user is listening to, a sound in a band close to the frequency of driving noise or tire traveling noise generated when the vehicle is traveling. Can no longer be heard. In particular, when driving a car, the noise is often low frequency, and in audio that can reproduce this low frequency, the above effect may be reduced to the same level as normal audio. Results in wasted consumption.

  In recent years, the development of electric vehicles has progressed, and the power consumption of the entire electric vehicle affects the travel distance. Therefore, it is desirable to suppress the power consumption even in the audio or amplifier mounted on the electric vehicle.

  As a countermeasure, Patent Document 1 discloses a technique for stopping the function of a subwoofer amplifier when the volume is equal to or lower than a predetermined level in an electronic musical instrument including a subwoofer amplifier that amplifies a bass signal or a sound effect. It is disclosed.

JP 2007-81812 A

  However, the technique disclosed in Patent Document 1 described above has a problem that it cannot be applied when a subwoofer amplifier is not provided.

  The present invention has been made to solve the above-described problems, and even when a predetermined woofer amplifier is not provided, the low-frequency sound signal is removed to suppress the power consumption of the amplifier. Objective.

  The amplifier according to the present invention has a volume adjusting unit that adjusts the volume of the input sound signal, a high-pass filter that attenuates a low frequency component of the input sound signal, and a volume adjusted by the volume adjusting unit. A determination unit that determines whether or not the volume is less than a volume threshold, and when the volume adjusted by the volume adjustment unit by the determination unit is determined to be less than the volume threshold, the input sound signal is used as a high-pass filter. And a signal control unit for outputting.

  According to the present invention, it is possible to reduce the power consumption of the amplifier and to realize an audio output that is audibly natural.

FIG. 3 is a block diagram illustrating configurations of an amplifier and a mobile information device according to the first embodiment. 3 is a flowchart showing an operation of a mobile information device including an amplifier according to the first embodiment. FIG. 6 is a block diagram illustrating a configuration of an amplifier and mobile information device according to a second embodiment. 6 is a flowchart showing an operation of a mobile information device including an amplifier according to the second embodiment. FIG. 10 is a block diagram illustrating configurations of an amplifier and a mobile information device according to Embodiment 3. 14 is a flowchart showing the operation of the in-vehicle audio apparatus including the amplifier according to the third embodiment.

Embodiment 1 FIG.
1 is a block diagram showing a configuration of an amplifier and a mobile information device according to Embodiment 1 of the present invention. In FIG. 1, an amplifier 1 includes a moving speed calculation unit 2, a power saving control unit (determination unit) 3, a signal control unit 4, a high-pass filter 5, a volume adjustment unit 6, and a speaker amplifier 7. In addition, a mobile body information device is configured by connecting the mobile body information acquisition unit 21, the sitting position detection unit 22, the audio unit 23, the speaker 24, and the notification unit 25 to the amplifier 1. The mobile information device is, for example, an in-vehicle navigation device or an in-vehicle audio device.

Details of each component shown in FIG. 1 will be described.
The moving body information acquisition unit 21 acquires acceleration of the moving body, vehicle speed pulses, and the like. The moving speed calculation unit 2 calculates the moving speed of the moving body from the acceleration and vehicle speed pulse acquired by the moving body information acquiring unit 21. For example, when the moving body is an automobile, the seating position detection unit 22 detects a seat where a user or a passenger (hereinafter referred to as a user) is seated among seats of the automobile.

  The audio unit 23 is the farthest distance from the speaker 24 located in the vicinity of other seats except the seat where the seating of the user is detected by the seating position detection unit 22 or the seat where the seating of the user is detected. The speaker 24 located in the vicinity of the seat is selected as the speaker 24 set to the power saving state. Further, the audio unit 23 outputs a volume value set by the user via an operation input unit (not shown) to the volume adjustment unit 6.

  The power saving control unit 3 sets the volume threshold value of the speaker amplifier 7 according to the moving speed of the moving object calculated by the moving speed calculation unit 2, and the current speaker amplifier acquired from the set volume threshold value and the volume adjustment unit 6. The volume value of 7 is compared. When the current volume value of the speaker amplifier 7 is equal to or greater than the volume threshold value, control information for instructing the transition to the power saving state of the speaker 24 selected as being able to be set in the power saving state in the audio unit 23 is provided. Generate and output to the signal control unit 4.

  Based on the control information input from the power saving control unit 3, the signal control unit 4 includes an audio signal output from the speaker 24 that shifts to the power saving state among the plurality of audio signals input from the audio unit 23. If so, the audio signal is output to the high-pass filter 5 as an attenuated audio signal. On the other hand, the audio signal output from the speaker 24 that is not shifted to the power saving state is output to the volume adjusting unit 6 as a normal audio signal.

  The high pass filter 5 attenuates an audio signal having a frequency equal to or lower than a preset cutoff frequency for the attenuated audio signal input from the signal control unit 4. The volume adjusting unit 6 attenuates or amplifies the attenuated audio signal input from the high-pass filter 5 and the normal audio signal input from the signal control unit 4 according to the volume value set by the audio unit 23. The speaker amplifier 7 drives the speaker 24 and outputs the audio signal adjusted by the volume adjustment unit 6 from the speaker 24 as sound.

  The notification unit 25 notifies the user that the speaker 24 is operating with power saving when acquiring the control information for shifting any speaker 24 to the power saving state from the power saving control unit 3. The notification method can be variously configured. For example, a light emitting element such as an LED is turned on, a message such as “operating in a power saving state” is output by voice, or the display unit of the audio unit 23 or the navigation unit. (Not shown) is used to display a message such as “Operating in power saving state”. Moreover, you may alert | report so that the speaker 24 which has shifted to the power saving state can be specified, and you may alert | report collectively that it has shifted to the power saving state.

Next, the operation will be described.
FIG. 2 is a flowchart showing an operation flow of the mobile information device including the amplifier according to the first embodiment.
When the seating position detection unit 22 detects the seating position of the user (step ST1), the audio unit 23 refers to the seating position detected in step ST1 and is positioned in the vicinity of the seat where the user is not seated. The speaker 24 is selected as the speaker 24 to be shifted to the power saving state (step ST2). The moving body speed calculation unit 2 calculates the moving speed of the moving body from the moving body information acquired by the moving body information acquisition unit 21 (step ST3). The power saving control unit 3 calculates a volume threshold based on the moving speed of the moving body calculated in step ST3 (step ST4), and the new volume threshold calculated in step ST4 is a predetermined time before (for example, 1 minute before) It is determined whether or not the difference from the calculated sound volume threshold is within a predetermined range (step ST5).

  In step ST4, it is assumed that the power saving control unit 3 has a table in which a sound volume threshold value corresponding to each moving speed is set in advance. In this table, for example, when the moving speed of the moving body is fast, it is considered that the noise is large, and even if the audio signal in the low frequency range is attenuated to a high volume value, it does not become an unnatural sound. A high volume threshold is set. On the other hand, when the moving speed is 0 or close to 0, it is considered that the noise is small, and if the audio signal in the low frequency range is attenuated to a high sound volume value, it becomes unnatural to hear, so a low sound volume threshold is set. . The power saving control unit 3 refers to the table set in this way, and acquires a volume threshold value corresponding to the moving speed of the moving object calculated in step ST3.

  When the power saving control unit 3 determines that the difference between the calculated new volume threshold and the volume threshold calculated before a predetermined time is within the predetermined range (step ST5; YES), the volume threshold varies little, i.e., moves. It is determined that the moving speed of the body is stable, the calculated new volume threshold is set as the formal volume threshold (step ST6), and the process proceeds to step ST7. On the other hand, if it is determined that the difference exceeds the predetermined range (step ST5; NO), it is determined that the volume threshold value fluctuates frequently, i.e., the moving speed of the moving body is not stable, and the volume threshold value is not rewritten. The process proceeds to ST7.

  Further, the power saving control unit 3 refers to the volume value setting information output from the audio unit 23, and determines whether or not the volume value of the speaker amplifier 7 is currently being adjusted (step ST7). Whether or not the volume value of the speaker amplifier 7 is currently being adjusted may be determined by determining whether a certain time (for example, 1 second) has elapsed since the previous volume value was adjusted, or by the user When the volume value is adjusted, a signal indicating the start and end of the volume value adjustment may be output to the power saving control unit 3. Thereby, for example, while the user is turning the volume knob of the audio unit 23, the transition to the power saving state or the return to the normal state is performed, and the volume value can be prevented from changing suddenly. it can.

  If it is determined that the volume value of the speaker amplifier 7 is not being adjusted (step ST7; NO), the volume value of the speaker amplifier 7 that the power saving control unit 3 acquires from the volume adjustment unit 6 is equal to or greater than the set volume threshold value. Is determined (step ST8). When it is determined that the volume value of the speaker amplifier 7 is less than the volume threshold value (step ST8; NO), the power saving control unit 3 sets control information for shifting the speaker 24 selected in step ST2 to the power saving state. The audio signal output to the speaker 24 to be shifted to the power saving state based on the control information input to the signal control unit 4 is output to the high-pass filter 5 as an attenuated audio signal, and other audio signals are output to normal audio. A signal is output to the volume adjusting unit 6 (step ST9).

  The high-pass filter 5 attenuates the audio signal below the preset cutoff frequency for the attenuated audio signal input in step ST9, and outputs the attenuated audio signal to the volume adjusting unit 6 (step ST10). Furthermore, the power saving control unit 3 controls the notification unit 25 to notify that the selected speaker 24 has shifted to the power saving state (step ST11).

  On the other hand, if it is determined in step ST7 that the volume value of the speaker amplifier 7 is being adjusted (step ST7; YES), or if it is determined that the volume value of the speaker 24 is greater than or equal to the volume threshold value (step ST8; YES), The power saving control unit 3 does not shift to the power saving state, generates control information for outputting normal audio signals from all the speakers 24, outputs the control information to the signal control unit 4, and the signal control unit 4 is input. Based on the control information, all audio signals are output as normal audio signals to the volume adjusting unit 6 (step ST12).

  The volume adjusting unit 6 attenuates or amplifies the audio signal input in step ST9 and step ST10 or step ST12 based on the volume value set by the audio unit 23 (step ST13). The speaker amplifier 7 drives the speaker 24 to output the audio signal whose volume has been adjusted in step ST13 (step ST14). Thereafter, the flow returns to the process of step ST1, and the above-described process is repeated.

  As described above, according to the first embodiment, when the volume value set in the volume adjustment unit 6 is less than the volume threshold, the control information for generating the control information for shifting the predetermined speaker 24 to the power saving state is saved. The power control unit 3 and the signal control unit 4 that outputs the audio signal output from the speaker 24 that is shifted to the power saving state based on the control information generated in the power saving control unit 3 to the high-pass filter 5 as an attenuated audio signal. Since the amplifier is configured to be provided, it is possible to reduce the power consumption of the amplifier and to output a natural sound from the speaker.

  In addition, according to the first embodiment, the moving speed calculating unit 2 that calculates the moving speed of the moving body, the volume threshold value corresponding to the calculated moving body speed, and the calculated volume threshold value and the volume adjusting unit 6 are calculated. Since the power saving control unit 3 that compares the sound volume value set to the above is provided, the sound volume threshold value can be set in consideration of the tendency that the traveling noise increases in accordance with the traveling speed of the moving body. .

  Further, according to the first embodiment, the seating position detection unit 22 that detects the seating position of the user, the audio unit 23 that selects the speaker 24 to be shifted to the power saving state based on the detection result of the seating seat, And a power saving control unit 3 that generates control information for shifting the speaker 24 selected by the audio unit 23 to the power saving state when the volume value set in the volume adjusting unit 6 is less than the volume threshold. Since it comprised, even when a predetermined speaker transfers to a power saving state, a user can be made hard to feel a change of a sound.

  In addition, according to the first embodiment, when the difference between the new volume threshold calculated by the power saving control unit 3 and the volume threshold calculated before a predetermined time is within a predetermined range, the volume threshold is set. Therefore, it is possible to prevent frequent fluctuations in the sound volume threshold value and to prevent unnatural fluctuations in low-frequency sound volume.

  According to the first embodiment, when the user is adjusting the volume via the operation input unit of the audio unit 23, the audio signal is not attenuated by the high-pass filter 5, It is possible to prevent the shift to the power saving state during the user's volume adjustment and prevent a sudden change in the volume value.

Embodiment 2. FIG.
In the amplifier according to the second embodiment, a volume threshold is set according to the magnitude of noise under the usage environment of the amplifier 1, and more efficient power saving of the amplifier 1 can be achieved, resulting in a more natural audio output. Is realized.
FIG. 3 is a block diagram showing a configuration of an amplifier and mobile information device according to Embodiment 2 of the present invention. Instead of the moving body information acquisition unit 21 and the movement speed calculation unit 2 having the configuration described in FIG. 1 in the first embodiment, the sound collection unit 26, the low-pass filter 8, the echo canceller 9, and the noise power measurement unit 10 are provided. In addition, an operation unit 23 a is provided in the audio unit 23 instead of the seating position detection unit 22. In the following, the same or corresponding parts as the components of the amplifier 1 according to the first embodiment are denoted by the same reference numerals as those used in the first embodiment, and the description thereof is omitted or simplified.

  The sound collection unit 26 is composed of, for example, a microphone, and collects sound under the usage environment of the amplifier 1 including sound generated through the speaker 24. In addition, in order to suppress the sound collection of the sound generated through the speaker 24, the sound is collected only when the sound generated through the speaker 24 is smaller than a preset reference value. Also good. The low-pass filter 8 extracts only a signal having a frequency equal to or lower than a frequency scheduled to be attenuated by the high-pass filter 5 disposed in the subsequent stage from the sound signal collected by the sound collection unit 26 as a noise signal.

  The echo canceller 9 removes an audio signal generated from the speaker 24 as an echo from the noise signal extracted by the low-pass filter 8. The audio signal generated from the speaker 24 as an echo to be removed is obtained from the output signal of the speaker amplifier 7. The noise power measuring unit 10 calculates the power value of the noise signal from which echoes have been removed by the echo canceller 9 and outputs the power value to the power saving control unit 3.

  The power saving control unit 3 sets a volume threshold value of the speaker amplifier 7 according to the power value of the noise signal input from the noise power measurement unit 10, and the current speaker acquired from the set volume threshold value and the volume adjustment unit 6 The volume value of the amplifier 7 is compared. When the current volume value of the speaker amplifier 7 is equal to or greater than the volume threshold value, control information for instructing the transition to the power saving state of the speaker 24 selected as being able to be set in the power saving state in the audio unit 23 is provided. Generate and output to the signal control unit 4.

  The operation unit 23a includes an operation panel and operation buttons that can be input by the user, and sets the speaker 24 to be shifted to a power saving state. For example, the speaker 24 located near the seat where the user is not seated is set to shift to the power saving state, and the woofer speaker or the subwoofer speaker that plays mainly the audio signal in the low frequency range is set in the power saving state. The user can arbitrarily select the speaker 24 to be shifted to the power saving state, such as setting to shift to The audio unit 23 outputs the speaker information to be shifted to the power saving state selected via the operation unit 23a to the power saving control unit 3.

Next, the operation will be described.
FIG. 4 is a flowchart showing the operation flow of the mobile information device including the amplifier according to the second embodiment. In the following, the same steps as those of the amplifier 1 according to the first embodiment are denoted by the same reference numerals as those used in FIG. 2, and the description thereof is omitted or simplified.
When the user sets the speaker 24 via the operation unit 23a (step ST21), the audio unit 23 selects the speaker 24 to be shifted to the power saving state based on the setting of step ST21 (step ST22).

  The sound collection unit 26 collects sound under an amplifier usage environment (step ST23). Only the noise signal is acquired from the sound collected in step ST23 via the low pass filter 8 and the echo canceller 9 (step ST24). Specifically, the collected sound is limited to a frequency signal in a band to be attenuated by the low-pass filter 8 and the subsequent high-pass filter 5. Further, the echo of the audio signal emitted from the speaker 24 is removed by passing through the echo canceller 9. In this way, only the noise signal is acquired by passing through the low-pass filter 8 and the echo canceller 9.

  The noise power measurement unit 10 measures the power value of the noise signal acquired in step ST24 (step ST25). The power saving control unit 3 calculates a new volume threshold based on the power value of the noise signal measured in step ST25 (step ST26), and the new volume threshold calculated in step ST26 is a predetermined time before (for example, 1). It is determined whether or not the difference from the volume threshold value calculated a minute ago is within a predetermined range (step ST5).

  In step ST26, it is assumed that the power saving control unit 3 has a table in which a volume threshold value corresponding to the power value of each noise signal is set in advance. In this table, for example, when the power value of the noise signal is high, it is considered that the noise is high, and even if the audio signal in the low frequency range is attenuated to a high volume value, it does not become an unnatural sound. A high volume threshold is set. On the other hand, when the power value of the noise signal is small, it is considered that the noise is small, and if the audio signal in the low frequency range is attenuated to a high sound volume value, it becomes unnatural for hearing, so a low sound volume threshold is set. The power saving control unit 3 refers to the table set in this way, and acquires a volume threshold corresponding to the power value of the noise signal measured in step ST25.

  When the power saving control unit 3 determines that the difference between the calculated new volume threshold and the volume threshold calculated a predetermined time is within the predetermined range (step ST5; YES), the volume threshold is less changed, that is, It is determined that the power value of the noise signal (moving speed of the moving body) is stable, the calculated new volume threshold is set as the formal volume threshold (step ST6), and the process proceeds to step ST7. On the other hand, if it is determined that the difference exceeds the predetermined range (step ST5; NO), it is determined that the volume threshold value varies greatly, that is, the power value of the noise signal (moving speed of the moving body) is not stable, and the volume threshold value is determined. The process proceeds to step ST7 without rewriting. Thereafter, the flow performs the same processing as steps ST7 to ST14 shown in the first embodiment.

  As described above, according to the second embodiment, the noise power measuring unit 10 that measures the power value of the noise signal under the usage environment of the amplifier 1 and the volume threshold corresponding to the power value of the noise signal are set. Since it is configured to include the power saving control unit 3 that sets the speaker 24 to be shifted to the power saving state using the volume threshold value, it becomes possible to set the speaker using the actually measured noise. Power saving that enables efficient and more natural audio output can be realized.

  In addition, according to the second embodiment, the low-pass filter 8 that restricts the sound signal collected by the sound collecting unit 26 to the frequency band attenuated by the high-pass filter 5 when the power saving state is shifted is provided, and the frequency band is restricted. Since the sound volume threshold value corresponding to the power value of the noise signal is set, it is possible to accurately determine whether the audio band attenuated by the high-pass filter 5 is actually buried in noise.

  Further, according to the second embodiment, since the user can select the speaker 24 to be shifted to the power saving state via the operation unit 23a, the speaker can be controlled according to the user's preference.

Embodiment 3 FIG.
In the amplifier according to the third embodiment, a volume threshold is set in accordance with the amount of noise in the usage environment of the amplifier 1 as in the second embodiment, and shows another configuration example.
FIG. 5 is a block diagram showing a configuration of an amplifier and mobile information device according to Embodiment 2 of the present invention. Instead of the low-pass filter 8 having the configuration described with reference to FIG. 3 in the second embodiment, a frequency band converter 11 and a noise band detector 12 are provided. The audio unit 23 includes a speaker setting unit 23b that automatically sets the speaker 24 to be shifted to the power saving state.
In the following description, the same or corresponding parts as those of the amplifier 1 according to the first and second embodiments are denoted by the same reference numerals as those used in the first and second embodiments. Omit or simplify.

  The sound collection unit 26 is composed of, for example, a microphone, and collects sound under the usage environment of the amplifier 1 including sound generated through the speaker 24. In addition, in order to suppress the sound collection of the sound generated through the speaker 24, the sound is collected only when the sound generated through the speaker 24 is smaller than a preset reference value. Also good. The echo canceller 9 removes the audio signal generated from the speaker 24 that is an echo from the sound collected by the sound collection unit 26, and outputs it to the noise power measurement unit 10 and the frequency band conversion unit 11. The audio signal generated from the speaker 24 as an echo to be removed is obtained from the output signal of the speaker amplifier 7.

  The noise power measuring unit 10 calculates the power value of the noise signal from which echoes have been removed by the echo canceller 9 and outputs the power value to the power saving control unit 3. The frequency band converter 11 performs a Fourier transform on the noise signal from which the echo has been removed by the echo canceller 9 to calculate a noise spectrum. The noise band detection unit 12 detects a noise band from the noise spectrum calculated by the frequency band conversion unit 11 and calculates the maximum frequency within the detected noise band. Further, a filter coefficient having the calculated maximum frequency as a cutoff frequency is calculated and set in the high-pass filter 5. The high-pass filter 5 sets a cut-off frequency from the filter coefficient set by the noise band detection unit 12 and attenuates an audio signal in the same band as the noise signal.

  The power saving control unit 3 sets a volume threshold value of the speaker amplifier 7 according to the power value of the noise signal input from the noise power measurement unit 10, and the current speaker acquired from the set volume threshold value and the volume adjustment unit 6 The volume value of the amplifier 7 is compared. When the current volume value of the speaker amplifier 7 is less than the volume threshold, control information for instructing the transition to the power saving state of the speaker 24 selected to be set in the power saving state in the audio unit 23 is provided. Generate and output to the signal control unit 4. The speaker setting unit 23b of the audio unit 23 has in advance setting information of a speaker 24 (for example, a woofer speaker or a subwoofer speaker that plays back mainly an audio signal in a low frequency range) to be shifted to a power saving state.

Next, the operation will be described.
FIG. 6 is a flowchart showing an operation flow of the mobile information device including the amplifier 1 according to the third embodiment. In the following, the same steps as those of the mobile information device including the amplifier 1 according to the first and second embodiments are denoted by the same reference numerals as those used in FIG. 2 or FIG. Simplify.
When the speaker 24 information to be shifted to the power saving state is output from the speaker setting unit 23b of the audio unit 23 (step ST31), the sound collecting unit 26 collects the sound under the environment where the amplifier 1 is used (step ST32). . The echo canceller 9 removes the echo of the audio signal emitted from the speaker 24 from the sound collected in step ST32, so that the noise power measuring unit 10 and the frequency band converting unit 11 acquire only the noise signal (step ST33). ).

  The noise power measurement unit 10 measures the power value of the noise signal acquired in step ST33 (step ST25). The power saving control unit 3 calculates a new volume threshold based on the power value of the noise signal measured in step ST25 (step ST26), and the new volume threshold calculated in step ST26 is a predetermined time before (for example, 1). It is determined whether or not the difference from the sound volume threshold calculated a minute ago is within a predetermined range (step ST5). In step ST26, it is assumed that the power saving control unit 3 has a table in which a volume threshold value corresponding to the power value of each noise signal is set in advance as in the second embodiment.

  When the power saving control unit 3 determines that the difference between the calculated new volume threshold and the volume threshold calculated before a predetermined time is within the predetermined range (step ST5; YES), the volume threshold varies little, that is, noise. It is determined that the power value of the signal (moving speed of the moving body) is stable, the calculated new volume threshold is set as the formal volume threshold (step ST6), and the process proceeds to step ST34. On the other hand, if it is determined that the difference between the sound volume thresholds exceeds the predetermined range (step ST5; NO), it is determined that the sound volume threshold value is largely varied, that is, the power value of the noise signal (moving speed of the moving object) is not stable. The process proceeds to step ST34 without rewriting the volume threshold.

  The frequency band converter 11 performs a Fourier transform on the noise signal acquired in step ST33 to calculate a noise spectrum, and calculates the maximum frequency in the noise band detected from the noise spectrum calculated in the noise band detector 12 (step ST34). ). Furthermore, the noise band detection unit 12 determines whether or not the difference between the maximum frequency calculated in step ST34 and the maximum frequency calculated before a predetermined time (for example, one minute before) is within a predetermined range. Is performed (step ST35).

  When the noise band detector 12 determines that the difference between the calculated new maximum frequency and the maximum frequency calculated a predetermined time before is within a predetermined range (step ST35; YES), it is determined that there is little noise fluctuation. Then, a filter coefficient having the calculated new maximum frequency as a cutoff frequency is calculated and set in the high-pass filter 5 (step ST36), and the process proceeds to step ST7. On the other hand, if it is determined that the maximum frequency difference exceeds the predetermined range (step ST35; NO), the process proceeds to step ST7 without rewriting the filter coefficient of the high-pass filter 5. Thereafter, the flow performs the same processing as steps ST7 to ST14 shown in the first embodiment, returns to the processing of step ST32, and repeats the above-described processing.

  As described above, according to the third embodiment, the frequency band converting unit 11 that calculates the noise spectrum by Fourier-transforming the noise signal from which the echo is removed by the echo canceller 9, and the maximum frequency of the noise band from the noise spectrum. And the noise band detection unit 12 that calculates the filter coefficient using the maximum frequency as a cutoff frequency and sets the filter coefficient in the high-pass filter 5 is provided. Therefore, when shifting to the power saving state, the frequency of the noise signal is calculated. The high pass filter can be set to attenuate only the audio signal in the band. Furthermore, the audio signal can be attenuated according to the noise situation, and the power consumption of the amplifier can be efficiently reduced.

  In the first to third embodiments, the selection of the speaker 24 to be shifted to the power saving state is automatically set by the configuration using the seating position detection unit 22, the configuration using the operation unit 23a, and the speaker setting unit 23b. Each of the configurations is shown, but can be appropriately configured according to the application. Moreover, although the seating position detection part 22 showed the structure made into the external structure of the audio unit 23, you may comprise in the audio unit 23, and may be comprised.

  In the above-described first to third embodiments, the configuration in which the notification unit 25 is configured as the external configuration of the amplifier 1 and the audio unit 23 has been described. However, the notification unit 25 may be incorporated in the audio unit 23.

  In the present invention, within the scope of the invention, any combination of the embodiments, or any modification of any component in each embodiment, or omission of any component in each embodiment is possible. .

  DESCRIPTION OF SYMBOLS 1 Amplifier, 2 Movement speed calculation part, 3 Power saving control part, 4 Signal control part, 5 High pass filter, 6 Volume adjustment part, 7 Speaker amplifier, 8 Low pass filter, 9 Echo canceller, 10 Noise power measurement part, 11 Frequency band Conversion unit, 12 noise band detection unit, 21 mobile body information acquisition unit, 22 seating position detection unit, 23 audio unit, 23a operation unit, 23b speaker setting unit, 24 speaker, 25 notification unit, 26 sound collection unit.

Claims (12)

In an amplifier that adjusts the volume of an input sound signal and generates an output signal to be output to a speaker,
A volume adjuster for adjusting the volume of the input sound signal;
A high-pass filter that attenuates low-frequency components of the input sound signal;
A determination unit that determines whether or not the volume adjusted by the volume adjustment unit is less than a volume threshold;
A signal control unit that outputs the input sound signal to the high-pass filter when the determination unit determines that the volume adjusted by the volume adjustment unit is less than a volume threshold; The amplifier that features. Provided with a speed detection unit for detecting the moving speed of the moving body equipped with the amplifier,
The amplifier according to claim 1, wherein the determination unit changes the volume threshold value to a value corresponding to a moving speed detected by the speed detection unit. A noise measuring unit that measures the intensity of noise included in the collected sound signal collected by the external sound collecting unit,
The amplifier according to claim 1, wherein the determination unit changes the volume threshold to a value corresponding to a noise intensity measured by the noise measurement unit. An echo canceller for removing the output signal of the amplifier from the collected sound signal collected by the external sound collecting unit;
The amplifier according to claim 3, wherein the noise measurement unit measures the output intensity of the echo canceller as the noise intensity. A low-pass filter that passes only a low-frequency band that is attenuated by the high-pass filter from the collected sound signal collected by the external sound collecting unit;
The amplifier according to claim 4, wherein the echo canceller removes an output signal of the amplifier from a sound signal that has passed through the low-pass filter. A frequency band converter that detects a frequency band of the output of the echo canceller and calculates a noise spectrum;
A noise band detector for detecting a maximum frequency in the frequency band of the noise spectrum calculated by the frequency band converter;
5. The amplifier according to claim 4, wherein the maximum frequency of the noise spectrum detected by the noise band detection unit is set as a cutoff frequency of the high-pass filter.   When the volume control operation is executed from the outside, the signal control unit outputs the input sound signal to the volume control unit without passing through the high-pass filter and outputs a volume corresponding to the volume control operation. The amplifier according to claim 1, wherein the amplifier is adjusted.   In the case where the signal control unit generates an output signal to a speaker located in the vicinity of a seat where an occupant is seated in the moving body or a speaker selected in advance by an external operation, the input sound signal is The amplifier according to claim 1, wherein the amplifier is output to the volume adjusting unit without passing through the high-pass filter.   The determination unit, when changing the volume threshold, uses the new volume threshold for determination if the difference between the new volume threshold and the volume threshold before a predetermined time is within a predetermined range. Item 1. The amplifier according to item 1. A plurality of speakers mounted on a moving object;
A mobile information device comprising the amplifier according to claim 1, wherein a volume of an input sound signal is adjusted and output to the plurality of speakers.   The mobile information device according to claim 10, further comprising a notification unit that notifies that the low-frequency component of the sound signal input by the amplifier is attenuated by the high-pass filter. In the power saving method of the amplifier that adjusts the volume of the input sound signal and generates an output signal to be output to the speaker,
A volume adjusting unit adjusting the volume of the input sound signal;
A high-pass filter attenuates a low-frequency component of the input sound signal;
A step of determining whether or not the adjusted volume is less than a volume threshold;
The signal control unit includes a step of outputting the input sound signal to the high-pass filter when it is determined that the adjusted volume is less than a volume threshold. Method.

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