JP2010141571A - Volume control method, audio signal reproduction device, and program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve sound distortion, sound cracking, SN ratio in an audio signal reproduction device having digital signal processing. <P>SOLUTION: A digital sound signal input from a DSP 5 is converted into an analog sound signal by a D/A converter 8 after gain control is performed by a digital gain setting part 7, input to a receiver 1 via an amplifier 10 for receivers after gain control is performed by an analog gain setting part 9, and output as sound from the receiver 1. Gains of the digital gain setting part 7 and the analog gain setting part 9 are set, to a plurality of specified volume setting values, to larger values as the volume setting values become larger, and gain allocation ratio of set gains in the digital gain setting part 7 and the analog gain setting part 9 is set so that the set gain in the digital gain setting part 7 may become larger as the volume setting value is smaller. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a technique for reproducing audio signals such as voice and music by digital signal processing, and more particularly to a reproduction volume adjustment technique.

  Receivers for mobile phones and other receivers are originally of a large type that has a dedicated low-pitched sound and a sufficient volume, so that the characteristics of the receiver parts themselves can be easily tuned. ing. For this reason, there are few problems such as distortion, sound cracking, SN ratio being bad and floor noise (noise) being noticeable at the time of reception.

  On the other hand, recently, liquid crystal screens have tended to expand significantly due to digital TV compatibility, pursuing ease of viewing, consideration for universality, etc. On the other hand, mobile phones themselves are mainly thinner and smaller. It is becoming. This makes it necessary to reduce the size and thickness of the receiver, and there are also those that use the speaker as a receiver so that it can also be used as a speaker.

  Therefore, in order to secure the volume and sound quality equivalent to the conventional receiver for receiving, there is no choice but to adjust the output from the receiver by raising the input level or adjusting the frequency characteristics. Therefore, the problem is that distortion, sound cracking due to excessive input, and particularly the analog gain is increased too much, the SN ratio deteriorates, and floor noise is easily heard, or because of the characteristics of parts, it is used for calls. There are problems such as floor noise outside the frequency band becoming conspicuous.

  Although not the volume adjustment of the mobile communication terminal, Patent Document 1 discloses that the volume adjustment value instructed by the volume adjustment switch is decomposed into a coarse adjustment value having a large adjustment unit and a fine adjustment value having a small adjustment unit. Is output to the digital attenuating means, and the digital attenuating means attenuates the digital signal with the degree of attenuation corresponding to the fine adjustment value. The coarse adjustment value is output to the electronic volume, and the analog signal input to the electronic volume is converted into an analog signal. A technique is described in which sound volume adjustment in a sound reproduction apparatus that performs digital signal processing can be performed without damaging the distortion rate / S / N ratio by attenuating at an attenuation degree corresponding to the coarse adjustment value.

Japanese Patent Laid-Open No. 7-240647

  As a volume adjustment method to ensure the volume and sound quality equivalent to a conventional receiver for receiving, when the input level is distributed between digital gain and analog gain and amplified, the reduction of floor noise is more important than distortion and sound cracking. If you do this, set a large gain on the digital gain side and make adjustments to reduce the gain on the analog side. Conversely, if you place more importance on reducing distortion and sound cracking than floor noise (noise), A method is conceivable in which a large gain is set on the analog gain side and fine adjustment is performed to suppress the gain on the digital side.

  However, there are the following problems to secure a rich volume and sound quality in the received voice of the mobile phone using such a method. 3 to 6 show the relationship between the digital processing and analog processing gain distribution and the input level in such a conventional model.

  In the following model, it is assumed that there are six levels of volume setting from 1 to 6, and (a) in the figure is when the volume setting value is 1 (minimum volume) and when the volume setting value is 6 (maximum volume). And the respective floor noise levels are shown, and (b) in the figure shows an example of gain distribution at each volume setting value. Since the floor noise is mainly generated in the analog part, it is increased by the increment of the analog gain, and is not affected by the increment of the digital gain. The dotted line shown in the upper part of the figure represents the maximum allowable amplitude input level.

  FIG. 3 shows a model in which a gain is set for each volume in the digital unit, and a fixed gain is set in the analog unit. For a certain level of input signal, the digital gain setting unit sets the gain according to the volume setting values 1 to 6. In this example, the level is increased, the level is further increased by the fixed value in the analog gain setting unit, and finally the level is further increased by the fixed value in the receiver amplifier unit and input to the receiver. The input levels to the receiver all represent the same level in FIGS.

  The floor noise is related to the analog gain, and the floor noise increases by the analog gain. Accordingly, when the volume is 6, S / N is indicated by a hatched double-ended arrow, and when the volume is 1, S / N is indicated by an open double-ended arrow. In this case, since the analog gain does not change between the volume 1 and the volume 6, the floor noise also does not change between the volume 1 and the volume 6. Therefore, when the volume is 1, the S / N is deteriorated.

  FIG. 4 shows a model in which the digital part has a fixed gain and the analog part has a gain set for each volume. Contrary to FIG. 3, for a certain level of input signal, a level corresponding to a fixed value is set by the digital gain setting part. Then, the analog gain setting unit raises the level according to the volume setting values 1 to 6, and finally the receiver amplifier unit further raises the level by a fixed value and inputs to the receiver.

  In this case, the floor noise also increases by the analog gain, so the S / N of the double-headed arrow with volume 6 and the white double-ended arrow of volume 1 have the same S / N. When the analog gain is 6, the floor noise itself becomes large and the floor noise becomes conspicuous in the silent state.

  Fig. 5 shows a model in which the gain necessary for the digital part is set for each volume, and the analog part is a model in which the gain is suppressed. The gain setting unit raises the level according to the volume setting value including the gain amount necessary for the next analog gain setting unit, the fixed value is 0 dB in the next analog gain setting unit, and finally the receiver amplifier unit Shows the case where the level is raised by a fixed value and input to the receiver.

  In this case, the floor noise increases only by the amount raised by the receiver amplifier unit, so the S / N is very good when the volume is 6. In addition, since the floor noise level can be suppressed to the maximum, the floor noise including the silent state becomes very inconspicuous, but conversely, since the gain in the digital gain setting unit increases, The dynamic range becomes very narrow as indicated by the hatched up arrow, and distortion and sound cracking are likely to occur in the digital part.

  FIG. 6 shows a model in which the gain in the digital part is suppressed as much as possible, and the gain as much as necessary in the analog part is set for each volume. In this example, the digital part is designed to prevent distortion and sound cracking. The digital gain setting unit has a fixed value of 0 dB for an input signal at a certain level, and the next analog gain setting unit requires the digital gain setting unit. In this example, the level is increased according to the gain including the gain amount and the sound volume setting values 1 to 6, and finally the level is increased by a fixed value by the receiver amplifier unit and input to the receiver.

  In this case, the dynamic range becomes very wide as shown by the up arrow with a diagonal line at the set volume 6 and the white upward arrow at the volume 1, and distortion and sound cracking in the digital part hardly occur, but in the analog part. Since a considerable amount of gain is raised, the floor noise is very bad and the S / N is similarly bad.

  In this way, when the input level is distributed between the digital gain and the analog gain in order to improve the receiver characteristics in the reception of the received voice of the mobile phone, a large gain setting is made on the digital gain side and the gain on the analog side is suppressed. If reduction of floor noise is emphasized, the frequency of distortion and sound cracking increases, and conversely, if a large gain is set on the analog gain side and the gain on the digital side is suppressed, distortion and sound cracking occur. However, the floor noise (noise) increases and it is difficult to improve both distortion, sound cracking and noise.

  An object of the present invention is to provide an audio signal reproducing apparatus having digital signal processing capable of solving the above-described problems.

  A volume adjustment method of the present invention includes a digital gain setting unit that performs gain adjustment of an input digital audio signal, a D / A converter that converts the digital audio signal gain-adjusted by the digital gain setting unit into an analog audio signal, and In an audio signal reproduction device having an analog gain setting unit that adjusts the gain of the converted analog audio signal, and a receiver amplifier that amplifies the analog audio signal gain-adjusted by the analog gain setting unit and outputs the amplified signal to the receiver In the volume adjustment method, the gain setting means increases each gain in the digital gain setting unit and the analog gain setting unit to a larger value as the volume setting value is larger than a plurality of designated volume setting values. In addition to setting, the gain set in the digital gain setting unit and the analog gain The gain distribution ratio setting gain in tough, as the volume setting value is small, and sets a large proportion of setting gain in the digital gain setting unit.

  An audio signal reproduction apparatus according to the present invention includes a digital gain setting unit that performs gain adjustment of an input digital audio signal, and a D / A converter that converts the digital audio signal gain-adjusted by the digital gain setting unit into an analog audio signal And an analog gain setting unit that performs gain adjustment of the converted analog audio signal, and an amplifier for receiver that amplifies the analog audio signal gain-adjusted by the analog gain setting unit and outputs the amplified signal to the receiver In the digital gain setting unit and the analog gain setting unit, each gain in the digital gain setting unit is set to a larger value as the volume setting value is larger than a plurality of designated volume setting values. Set gain and gain gain set in the analog gain setting section The emission distribution ratio, the more the smaller volume setting value, characterized in that it comprises a gain setting means for setting a large proportion of setting gain in the digital gain setting unit.

  The program of the present invention includes a digital gain setting unit that performs gain adjustment of an input digital audio signal, a D / A converter that converts the digital audio signal gain-adjusted by the digital gain setting unit into an analog audio signal, Provided in an audio signal reproduction device having an analog gain setting unit that adjusts the gain of the converted analog audio signal, and a receiver amplifier that amplifies the analog audio signal gain-adjusted by the analog gain setting unit and outputs the amplified signal to the receiver The computer is configured to set each gain of the digital gain setting unit and the analog gain setting unit to a larger value as the volume setting value is larger than a plurality of designated volume setting values. Set gain in the analog gain setting unit and gain in the analog gain setting unit The emission distribution ratio, the higher the volume setting value is smaller, characterized in that to function as a means to set a large proportion of setting gain in the digital gain setting unit.

  In the present invention, for example, in a mobile phone capable of switching the reception volume, both the digital gain and the analog gain are switched for each reception volume setting value of the reception voice, and the distribution of the analog gain and the digital gain is performed for each volume setting value. Since the volume is adjusted by changing the ratio so that the ratio of the set gain in the digital gain setting unit becomes larger as the volume setting value is smaller, distortion and sound cracking are reduced, and noise is reduced. Therefore, it is possible to provide reception voice reproduction with improved sound quality.

  In addition, by switching between digital gain and analog gain for each reception volume of the received voice, distortion, sound cracking and noise can be reduced, and the received voice reproduction can be improved regardless of the speaker and receiver characteristics. Can be provided.

  FIG. 1 is a circuit block diagram of a mobile phone with a reception volume adjustment function showing an embodiment of the present invention. Note that the circuit block of the mobile phone shown in FIG. 1 mainly shows the blocks related to the present invention, and does not show the blocks such as the radio communication unit not directly related to the present invention.

  In the mobile phone with the received sound volume adjustment function of this embodiment, the receiver 1 is a component that outputs voice and tone signals, and can be substituted as a speaker in this embodiment. A CPU (Central Processing Unit) 2 controls the entire mobile phone according to a control program stored in the memory 6 and performs processing / instructions related to various arithmetic processing related to speech / communication. As a related function, there is a function of executing processing such as a volume switching instruction such as a ring tone, voice, and transmission sensitivity. The configuration including the CPU 2 and the memory 6 has a function as a computer that executes various control programs of the mobile phone stored in the memory 6.

  The display unit 3 is connected to the CPU 2 and displays a selection screen at the time of function setting, a function setting status, an image, and the like. The operation unit 4 is connected to the CPU 2 and is operated by the user at the time of calling, starting / ending a call, menu, key input at the time of volume selection, and the operation information is input to the CPU 2.

  A DSP (Digital Signal Processor) 5 is connected to the CPU 2 and performs voice signal processing at the transmission / reception unit, signal processing of melody data such as ringtones, and the like. The memory 6 is connected to the CPU 2 and the DSP 5 and stores a program for the CPU 2 to control the operation of the mobile phone, and various function setting states such as a result calculated by the CPU 2 and a sound volume setting state.

  The digital gain setting unit 7 is connected to the CPU 2 and the DSP 5, receives gain information instructed by the CPU 2 in accordance with the volume setting value set by the user, switches the gain setting value to be used, The digital audio signal is amplified according to the set gain. The D / A converter 8 is connected to the digital gain setting unit 7 and converts the digital signal amplified by the digital gain setting unit 7 into an analog signal.

  The analog gain setting unit 9 is connected to the CPU 2 and the DA converter 8, receives gain information instructed from the CPU 2 according to the volume setting value set by the user, and switches the gain setting value to be used. The analog signal from the / A converter 8 is amplified according to the set gain. Here, the digital gain setting unit 7, the D / A converter 8, and the analog gain setting unit 9 may be configured as separate ICs or integrated ICs.

  The receiver amplifier unit 10 is connected to the analog gain setting unit 9 and is an audio amplifier having a fixed gain value. The receiver amplifier unit 10 amplifies the analog audio signal input from the analog gain setting unit 9 to obtain a final terminal. 1 is driven.

  FIG. 2 is a diagram showing an example of gain distribution in digital processing and analog processing when an input audio signal is sent to a receiver after being subjected to digital processing and analog processing in the mobile phone with the received sound volume adjustment function of this embodiment. It is.

  In this embodiment, it is assumed that there are six levels of volume setting. In the figure, the input when the volume setting value is 1 and the volume setting value is 6 and the respective floor noise levels are shown. Since the floor noise is mainly generated in the analog part, it is increased by the increment of the analog gain, and is not affected by the increment of the digital gain. A dotted line in the upper part represents the maximum allowable amplitude input level.

  In the present embodiment, as shown in FIG. 2, for a certain level of input signal, as the volume setting value increases, the gain in the digital gain setting unit 7 is increased to increase the signal level, and the next analog gain is set. Similarly to the digital gain setting unit 7, the setting unit 9 also increases the signal level by increasing the gain according to the volume setting value. At this time, the gain of the digital gain setting unit 7 and the gain of the analog gain setting unit 9 are set. The distribution ratio is set so that the set gain ratio in the digital gain setting unit 8 increases as the set sound volume value decreases.

  For example, as shown in FIG. 2B, when the set volume value is the smallest 1 (35 dB), the ratio of the gain in the digital gain setting unit 7 and the gain in the analog gain setting unit 9 is set to 17 dB to 2 dB. When the set volume value is 6 (60 dB), the ratio of the gain in the digital gain setting unit 7 and the gain in the analog gain setting unit 9 is set to 27 dB vs. 17 dB. Finally, the receiver amplifier unit 10 increases the level by a fixed value (16 dB). The numerical values shown in FIG. 2 (b) are convenient numerical values for explaining the present invention, and the present invention is not limited by the numerical values shown in FIG. 2 (b).

  Here, regarding floor noise, the floor noise also increases by the amount increased by the analog gain. Therefore, the S / N at the set volume value 6 in the present embodiment is the case of the set volume value 6 in FIG. It becomes substantially the same, and can be suppressed to be smaller than the floor noise at the set volume value 6 in FIG. On the other hand, in the case of the set volume value 1, in the example shown in FIG. 3, the analog gain unit amplifies 32 dB, whereas in the present embodiment, the analog gain unit is suppressed to a gain of 18 dB. S / N can be improved from the example shown in FIG.

  On the other hand, the dynamic range in the digital part can be ensured at the set volume value 6 substantially equal to the set volume value 6 in FIG. 3, and the dynamic range as at the set volume value 6 in FIG. Is never narrowed. In addition, the dynamic range in the case of the set volume value 1 is narrower than the dynamic range in the case of the set volume value 1 in FIG. There is no problem.

  As described above, in this embodiment, in the reproduction of the speaker and receiver reception voice of the mobile phone including the digital gain setting unit and the analog gain setting unit, the analog gain and the digital gain are distributed for each volume setting value of the input signal to the receiver. By changing and controlling the input signal, distortion, sound cracking and noise (floor noise) can be reduced, and sound quality can be improved.

  Next, the operation of the mobile phone according to the present embodiment will be described in detail with reference to FIGS.

  First, as a function, it is assumed that there are six levels of received sound volume setting values, and the selection of the received sound volume is performed. The memory 6 stores a sound volume setting value and a setting gain value in each gain section as a table as shown in FIG.

  The user operates the operation unit 4 to display the received sound volume on the display unit 5. Next, the operation unit 4 is operated while viewing the displayed reception volume, and the reception volume is set to 6, for example. The CPU 2 obtains information on the received sound volume 6 by referring to the above table stored in the memory 6, and gives instructions of 27 dB and 17 dB as gain setting values used for the digital gain setting unit 7 and the analog gain setting unit 9. put out. In response to the instruction, the digital gain setting unit 7 and the analog gain setting unit 9 individually switch and set the gain setting values to be used. This state is held in the memory 6.

  Here, when a call is actually made with the mobile phone, a digital signal of a certain voice is processed in the DSP 5 and inputted to the digital gain setting unit 7. Since the received sound volume 6 is set for the digital signal input to the digital gain setting unit 7, the digital signal is amplified by the gain value (27 dB) of the received sound volume 6 by the digital gain setting unit 7 and input to the D / A converter 8. The The digital signal amplified by the digital gain setting unit 7 is converted into an analog audio signal by the D / A converter 8 and input to the analog gain setting unit 9.

  The analog audio signal input to the analog gain setting unit 9 has the reception volume 6 set, and thus is amplified by the gain value (17 dB) of the reception volume 6 in the analog gain setting unit 9 and input to the receiver amplifier unit 10. Is done. The analog audio signal input to the receiver amplifier unit 10 is amplified by a fixed gain (16 dB) by the receiver amplifier unit 10 and then input to the receiver 1 and output from the receiver 1 as audio.

  When the caller operates the operation unit 4 and changes the set value of the reception volume to the volume 1, the gain value of the volume 1 set by the digital gain setting unit 7 and the analog gain setting unit 9 as described above, for example, The audio signal amplified by such a gain value is reproduced at a level of volume 1 from the receiver 1.

  As described above, in the present embodiment, with respect to an input signal at a certain level, the digital gain setting unit 7 raises the level according to the volume setting value, and the next analog gain setting unit 9 is similar to the digital gain setting unit 7. In accordance with the volume setting value, the level is increased. At this time, as the setting volume value becomes smaller, adjustment is performed for each volume setting value so that the gain of the analog gain setting unit 9 is decreased from the digital gain setting unit 7. Since the analog gain setting unit 9 is set to the minimum when the volume is 1, the S / N is improved from the maximum volume value to the minimum volume value, and a sufficient dynamic range is provided in the digital unit. Can be secured.

  In the above embodiment, the example of the received voice in the mobile phone has been described. However, the present invention is not limited to the above embodiment, and the present invention is not limited to the above embodiment, and the audio signal reproducing apparatus having the same configuration that performs sound reproduction and music reproduction with a speaker. Can be applied.

It is a circuit block diagram of a mobile phone with a received sound volume adjustment function showing an embodiment of the present invention. It is a figure which shows the example of each gain distribution at the time of carrying out the digital process and the analog process of the audio | voice signal in the mobile telephone with a reception volume adjustment function of this embodiment. It is a figure which shows the example of each gain allocation in the conventional model at the time of carrying out the digital process and the analog process of the audio | voice signal. It is a figure which shows the example of each gain allocation in the conventional model at the time of carrying out the digital process and the analog process of the audio | voice signal. It is a figure which shows the example of each gain allocation in the conventional model at the time of carrying out the digital process and the analog process of the audio | voice signal. It is a figure which shows the example of each gain allocation in the conventional model at the time of carrying out the digital process and the analog process of the audio | voice signal.

Explanation of symbols

1 Receiver 2 CPU
3 Display unit 4 Operation unit 5 DSP
6 Memory 7 Digital gain setting section 8 D / A converter 9 Analog gain setting section 10 Receiver amplifier

Claims (4)

A digital gain setting unit that performs gain adjustment of the input digital audio signal, a D / A converter that converts the digital audio signal gain-adjusted by the digital gain setting unit into an analog audio signal, and the converted analog audio signal A volume adjustment method in an audio signal reproduction device having an analog gain setting unit that performs gain adjustment of the receiver, and a receiver amplifier that amplifies the analog audio signal gain-adjusted by the analog gain setting unit and outputs the amplified signal to the receiver,
The gain setting means sets each gain in the digital gain setting unit and the analog gain setting unit to a larger value as the volume setting value is larger than a plurality of designated volume setting values, and the digital gain A volume adjustment method for setting a gain distribution ratio between a setting gain in a setting unit and a setting gain in the analog gain setting unit to a larger setting gain ratio in the digital gain setting unit as the volume setting value is smaller . A digital gain setting unit that performs gain adjustment of the input digital audio signal, a D / A converter that converts the digital audio signal gain-adjusted by the digital gain setting unit into an analog audio signal, and the converted analog audio signal In an audio signal reproduction device having an analog gain setting unit that performs gain adjustment of the receiver, and a receiver amplifier that amplifies the analog audio signal gain-adjusted by the analog gain setting unit and outputs the amplified signal to the receiver,
Each gain in the digital gain setting unit and the analog gain setting unit is set to a larger value as the volume setting value is larger than a plurality of designated volume setting values, and a setting gain in the digital gain setting unit And a gain setting means for setting a gain distribution ratio of the set gain in the analog gain setting section to a larger setting gain ratio in the digital gain setting section as the volume setting value is smaller. Signal reproduction device.   A portable communication terminal with a reception volume setting function, comprising the audio signal reproduction device according to claim 1. A digital gain setting unit that performs gain adjustment of the input digital audio signal, a D / A converter that converts the digital audio signal gain-adjusted by the digital gain setting unit into an analog audio signal, and the converted analog audio signal A computer provided in an audio signal reproducing apparatus having an analog gain setting unit that performs gain adjustment of the receiver and a receiver amplifier that amplifies the analog audio signal gain-adjusted by the analog gain setting unit and outputs the amplified signal to the receiver;
For each of a plurality of specified volume setting values, the larger the volume setting value is, the larger the gains of the digital gain setting unit and the analog gain setting unit are set, and the set gain in the digital gain setting unit And a program for causing the gain distribution ratio of the set gain in the analog gain setting unit to function as means for setting the set gain ratio in the digital gain setting unit to be larger as the volume setting value is smaller.

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