JP2008060673A - Mobile phone - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a mobile phone which outputs stereo sound by controling a wide effect so that a listener can easily lisen to the sound. <P>SOLUTION: In the case that an opening/closing detection part 110 detects a folded state of the mobile phone in a wide effect control part 101 provided in the mobile phone, a phase difference emphasis part 136 reduces the degree of enlargement of a phase difference between a left sound signal and a right sound signal of a stereo sound signal acquired from a sound source LSI, which is detected by a phase difference detection part 134, in comparison with that in a non-folded state of the mobile phone on the basis of a multiplication result resulting from multiplying a sound volume of the stereo sound signal detected by a sound volume detection part 133, by the phase difference. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a mobile phone that outputs an audio signal, and more particularly, to a technique for controlling a pseudo surround effect applied to the audio signal so as to facilitate listening.

Recently, mobile phones that are distributed in Japan mainly play music files in stereo with high sound quality. Since two speakers used for stereo reproduction are often arranged at very narrow intervals to ensure portability of the mobile phone, the sense of stereo sound spread (stereo feeling) received by the listener is considerably limited. ing.
As one of the techniques for improving the above-mentioned problem, Patent Document 1 discloses an effective surround effect by compensating for a decrease in the sound pressure level in the high frequency range of an audio signal by signal processing using a DSP (Digital Signal Processor). What is obtained is disclosed.

Here, the wide effect is to enhance a signal component having a sense of spread, that is, to enhance the difference in phase between the signals of the left and right channels and to increase the stereo feeling, and includes a surround effect and a pseudo surround effect.
JP 2004-349878 A

  However, in recent folding mobile phones, there are speakers used for music playback and ringing sounds that are close to the opposite housing when folded, and in such a folded state, When music having a surround effect is reproduced, a sound in which the phase difference between the left and right channels is emphasized is mixed in a very narrow space, which causes a problem that the sound pressure is lowered. This problem is not limited to the folding type, but also applies to an open / close type mobile phone such as a sliding type.

As a result, during music playback, the sound pressure decreases only for parts with a lot of reverberation that tend to cause a drop in sound pressure, and the sound pressure varies from part to part in the music. When unnaturalness is felt or an incoming call is received, a situation may occur in which the listener does not notice even though the ringtone is ringing due to a decrease in sound pressure.
In addition, when the ambient sound around the mobile phone is loud and the sound with the wide effect is output, the problem is that the output sound is unnatural and the listener does not notice the ring tone, as described above. Can occur.

  In view of the above problems, an object of the present invention is to provide a mobile phone that allows a listener to easily listen to a sound while outputting a sound that maintains a wide effect to some extent.

  In order to solve the above problems, the present invention provides a mobile phone that reproduces a stereo audio signal by applying a pseudo surround effect to an audio signal, and outputs the stereo audio signal to a speaker, and reduces the pseudo surround effect. A determination means for determining necessity, and a phase difference that is output to the output means by reducing the enhancement degree of the phase difference between the left sound signal and the right sound signal when the stereo sound signal is determined to be reduced. Emphasis means.

The mobile phone according to the present invention is provided with the above-described configuration, so that when the stereo sound becomes difficult to be heard by the listener by increasing the emphasis degree of the pseudo surround effect, the pseudo surround effect is reduced and the listener can listen. Easy stereo sound can be output.
Further, the mobile phone is of an openable type, the speaker is provided at a position exposed in the open state and facing inward in the closed state, and the determination means determines whether or not the own device is in the closed state and closes the mobile phone. In the case of the state, it may be determined that the pseudo surround effect needs to be reduced.

According to this configuration, in the openable mobile phone, when in the closed state, the wide effect is reduced, and the left and right audio signals are mixed in the minute gap to prevent the sound pressure from being reduced, It is possible to output sound capable of obtaining a volume feeling expected by the listener.
The mobile phone may be foldable and may be closed when folded.

According to this configuration, in the folding cellular phone, when it is in a folded state, the pseudo surround effect is reduced, and the left and right audio signals are mixed in the minute gap and the sound pressure is reduced. It is possible to output sound that can prevent the listener and obtain the volume feeling expected by the listener.
Further, the determination means may receive an input of environmental sound, determine whether or not the input sound volume is higher than a predetermined amount, and may determine that the pseudo surround effect needs to be reduced when the input sound volume is high.

According to this configuration, when the environmental sound around the mobile phone is loud, the pseudo surround effect can be reduced, clearer sound can be output, and stereo sound that can be easily heard by the listener can be output.
The phase difference emphasizing unit operates when it is determined that reduction is necessary, a phase difference calculation unit that calculates a phase difference value of the left audio signal and the right audio signal, and a volume value of the stereo audio signal A volume calculation unit that calculates the value, a multiplication unit that multiplies the calculated phase difference value, the volume value, and a predetermined enhancement that is applied when it is determined that reduction is necessary, according to the multiplication result value An emphasis unit that emphasizes a phase difference between the left audio signal and the right audio signal based on the degree; and an output unit that outputs the right and left audio signals with the phase difference enhanced to the output unit. It is good.

According to this configuration, the phase difference between the left and right audio signals of the stereo sound is emphasized based on an appropriate degree of enhancement predetermined according to the magnitude of the phase difference and the volume value, output, and listened to. It is possible to output stereo sound that is easy for a person to hear.
In addition, the enhancement degree corresponding to each multiplication result value less than a predetermined value is the same value, and the enhancement unit further determines the multiplication result value based on the same value when the multiplication result value is less than the predetermined value. The phase difference between the left audio signal and the right audio signal may be emphasized.

Further, the degree of enhancement corresponding to each multiplication result value greater than or equal to a predetermined value decreases at a constant rate corresponding to the increase in the multiplication result value, and the enhancement unit further has the multiplication result value greater than or equal to the predetermined value. In this case, the phase difference between the left audio signal and the right audio signal may be emphasized based on the enhancement degree corresponding to the multiplication result value.
According to this configuration, the unnaturalness felt by the listener can be eliminated by changing the degree of enhancement based on the multiplication result value, and stereo sound that is easy for the listener to output can be output.

Further, the enhancement unit converts the enhancement level from a left audio signal to a signal corresponding to the right audio signal based on a predetermined enhancement level corresponding to the multiplication result value applied when it is determined that reduction is necessary. A signal obtained by multiplying the right audio signal by a signal corresponding to the left audio signal may be subtracted from the right audio signal.
According to this configuration, the wide effect can be realized with a simple configuration in which the left audio signal and the right audio signal are reduced to each other according to the degree of enhancement.

The cellular phone according to the present invention is a folding cellular phone that outputs a stereo sound with a wide effect, and the degree of the wide effect applied to the stereo sound when the ambient sound such as ambient noise is large when folded. Is appropriately controlled to output the stereo sound.
Thus, when stereo sound is output in a state in which the mobile phone is folded, the listener expects the sound pressure to be reduced by mixing the left and right sound signals of the stereo sound in a minute gap. It prevents you from getting a sense of volume.

In addition, when playing music with stereo sound, the sound pressure drops only in parts with a lot of reverberation that tend to cause a drop in sound pressure, and the sound pressure varies from part to part in the music. This prevents situations where the listener feels unnatural when music is received, or when a call is received, due to a drop in sound pressure, the ringer is ringing.
In addition, when the environmental sound such as noise is large, the wide effect is reduced and clearer stereo sound is output, and sound that is easy for the listener to output while maintaining the wide effect is output.

Hereinafter, a mobile phone 100 according to an embodiment of the present invention will be described together with illustrated examples.
As shown in the front view of FIG. 1 and the side view of FIG. 2, the mobile phone 100 of the present invention comprises an upper housing 120 and a lower housing 130 that are connected in an openable / closable manner. The foldable mobile phone includes an L speaker 121 and an R speaker 122, and the lower housing 130 includes a microphone 151.

The mobile phone 100 has a function of reproducing stereo sound such as music, and when listening to music or detecting an incoming call, the L speaker 121 radiates the left channel sound of stereo sound, and the R speaker 122 outputs the right channel sound. Radiate.
The cellular phone 100 can take an open state as shown in FIGS. 1A and 2A and a closed state as shown in FIGS. 1B and 2B.

The mobile phone 100 has a function of a general mobile phone, and is further characterized by performing wide effect control.
Therefore, the wide effect control unit 101 that performs wide effect control in the mobile phone 100 will be described below with reference to FIGS.
Here, FIG. 3 is a block diagram showing a configuration of the wide effect control unit 101, and FIG. 4 is a diagram schematically showing a wide effect control process performed by the wide effect control unit 101.

  As shown in FIG. 3, the wide effect control unit 101 includes an audio LSI (not shown) that outputs a stereo audio left channel signal and a right channel signal related to music, a ringtone, and the like, an L speaker 121, and an R speaker 122. The AD converter 131, the AD converter 132, the volume detector 133, the phase difference detector 134, the multiplier 135, the phase difference enhancer 136, the DA converter 137, A DA converter 138, an amplifier 139, and an amplifier 140 are included.

  The AD converter 131 constantly receives a stereo audio left channel signal (analog signal) from the sound source LSI (step S101), and performs 16-bit AD (Analog to Digital) conversion at a predetermined sampling period. (Step S102), the left channel data (LD), which is 16-bit digital data as a result of AD conversion, is output to the sound volume detection unit 133, the phase difference detection unit 134, and the phase difference enhancement unit 136.

  Similar to the AD conversion unit 131, the AD conversion unit 132 constantly receives the right channel signal (analog signal) of stereo sound from the sound source LSI (step S111), and has a 16-bit precision AD at a predetermined sampling period. Conversion is performed, and right channel data (RD) that is 16-bit digital data as a result of AD conversion is output to the sound volume detection unit 133, the phase difference detection unit 134, and the phase difference enhancement unit 136.

Here, RD and LD indicate values of −32767 to 32767, and the sampling period is preferably as short as possible, but is determined at the time of design from the viewpoint of cost and the like.
The volume detector 133 detects the volume of stereo sound.
As an example of volume detection, the volume detection unit 133 receives LD from the AD conversion unit 131, receives RD from the AD conversion unit 132, and calculates the volume value AV by the following equation (step S103).

AV = (LD + RD + MA) / (2 × MA) (0 ≦ AV ≦ 1)
Here, MA is a predetermined offset value (MA = 32767 in this embodiment) that is the maximum value that LD and RD can take. MA is a value determined for the convenience of processing in order to correct the added value of LD and RD to a value of 0 or more. AV is normalized to a value of 0 to 1 by dividing LD + RD + MA by 2 × MA.

The sound volume detection unit 133 outputs AV to the multiplier 135.
The method for determining the volume value AV is an example, and the volume value may be obtained by another method.
The phase difference detection unit 134 calculates the phase difference between the left channel audio signal and the right channel audio signal.

  As an example of the phase difference calculation, the phase difference detection unit 134 receives the LD from the AD conversion unit 131, receives the RD from the AD conversion unit 132, and calculates the absolute value of the difference between the values indicated by the received LD and RD. Then, the absolute value is divided by 2 × MA to normalize to a value of 0 to 1, and the normalized result is output as a phase difference value (PV) to the multiplier 135 (step S113). PV is represented by the following formula.

PV = | LD-RD | / (2 × MA) (0 ≦ AV ≦ 1)
Multiplier 135 receives AV from volume detector 133, receives PV from phase difference detector 134, multiplies AV and PV, and outputs multiplication value MV, which is a multiplication result, to phase difference enhancer 136. (Step S131). MV is expressed by the following equation.
MV = AV × PV (0 ≦ MV ≦ 1)
The open / close detection unit 110 is an open / close sensor attached to a joint portion between the upper housing 120 and the lower housing 130, and the upper housing 120 and the lower housing 130 are either in the open state or the closed state. The open / close determination result JV having a value of 1 in the open state and 0 in the closed state is output to the phase difference emphasizing unit 136 (step S121).

The phase difference enhancement unit 136 acquires MV from the multiplier 135, acquires LD from the AD conversion unit 131, acquires JV from the open / close detection unit 110, and performs phase difference enhancement processing on the LD.
As an example of the phase difference enhancement process, the phase difference enhancement unit 136 first substitutes the acquired MV for the variable m used for the process (step S132).
Next, the phase difference emphasizing unit 136 determines whether JV is 1 or 0 (step S133).

The phase difference emphasizing unit 136 determines the mixing ratio n of LD and RD for performing the wide effect according to the graph shown in FIG. 5A when JV is 1, and when JV is 0. Is determined according to the graph shown in FIG.
When JV = 1 in step S133 (step S133: JV = 1), the phase difference emphasizing unit 136 determines n according to the following equation.

n = N (when 0 ≦ m ≦ 1-N) (step S142)
n = 1-m (when 1-N <m) (step S143)
In step S133, if JV = 0 (step S133: JV = 0), n is determined according to the following equation.
n = N ′ (when 0 ≦ m ≦ 1-N ′) (step S146)
n = 1-m (when 1-N ′ <m, N ′ <N) (step S147)
Here, N and N ′ satisfy N ′ <N, and specific values are determined at the time of system design.

Next, the phase difference enhancement unit 136 calculates the left channel enhancement data (LD ′) and the right channel enhancement data (RD ′) after the phase difference enhancement by the following formula using the mixing ratio n (step S151). .
LD ′ = LD−n × RD
RD ′ = RD−n × LD
Next, the phase difference enhancement unit 136 outputs LD ′ to the DA conversion unit 137 and outputs RD ′ to the DA conversion unit 138.

The DA conversion unit 137 receives LD ′ from the phase difference emphasizing unit 136, and performs DA (Digital to Analog) conversion on LD ′ (step S152).
Next, the amplifier 139 amplifies the analog signal resulting from the DA conversion of LD ′ (step S153), and the L speaker 121 radiates an audio signal based on the amplification result (step S154).

Also for RD ′, similarly to LD ′, the DA conversion unit 138 receives RD ′ from the phase difference enhancement unit 136 and DA-converts RD ′ (step S155).
Next, the amplifier 140 amplifies the analog signal that is a result of RD ′ being DA-converted (step S156), and R122 radiates an audio signal based on the amplification result.
Here, a supplementary explanation about correspondence of terms will be given.

The output means corresponds to a sound source LSI.
The open / close detection unit 110 corresponds to the determination unit.
The phase difference enhancement means includes a volume detection unit 133, a phase difference detection unit 134, a multiplier 135, a phase difference enhancement unit 136, a phase difference enhancement unit 136, a DA conversion unit 137, a DA conversion unit 138, an amplifier 139, and an amplifier 140. Is applicable.
<Modification>
Although the present invention has been described based on the above embodiment, it is needless to say that the present invention is not limited to the above embodiment. The following cases are also included in the present invention.

(1) In the above-described embodiment, switching between determining whether the mixing ratio n is determined using FIG. 5 (a) or FIG. 5 (b) depending on whether the cellular phone 100 is in an open state or a closed state. However, the present invention is not limited to this, and switching may be performed based on another trigger that can obtain the effect by switching the wide effect.
For example, the mixing ratio n may be switched using the volume input to the microphone while the user is not using the mobile phone 100.

Specifically, the wide effect control unit 102 shown in FIG. 6 is used instead of the wide effect control unit 101.
The wide effect control unit 102 is obtained by replacing the open / close detection unit 110 in the wide effect control unit 101 with an input sound volume detection unit 152. A microphone 151 is connected to the input volume detection unit 152.

The input volume detection unit 152 measures the amplitude of the audio signal acquired from the microphone 151, and when the amplitude is greater than or equal to a predetermined magnitude, the input volume detection unit 152 is in a closed state in the above-described embodiment with respect to the phase difference emphasizing unit 136. A corresponding value 0 is output, and if it is less than a predetermined size, a value 1 corresponding to the open state is output.
Since other operations are the same as those in the above-described embodiment, description thereof will be omitted.

By configuring as described above, when the mobile phone is placed in a quiet environment, a good stereo feeling (expansion feeling) can be obtained, and it is clearer than the stereo feeling under poor conditions such as a noise environment. It is possible to solve the problem that music is played with priority on feeling, or the user does not notice the incoming call by a clear telephone ringtone.
Here, a supplementary explanation will be given for the sound (noise level) acquired by the microphone 151.

  In addition, since the noise level at the library level is 40 dB and the noise level in a noisy city is generally referred to as 70 dB, the minimum value is N at the total volume collected by the microphone when the noise is 40 dB, and 70 dB. By allocating the mixing ratio in a stepless manner so that the maximum value N ′ is obtained when the amount of noise collected by the microphone at the time of noise is wide, it is possible to realize a wide effect in accordance with general noise.

However, since the sound from the speaker is not considered in the above condition, the above N allocation is considered according to the sensitivity (acoustic coupling) of the microphone collecting sound from its own solid speaker. Is required.
Since acoustic coupling varies depending on the casing design of the mobile phone terminal, microphone sensitivity, speaker volume, and the like, it is generally difficult to formulate. However, when designing a wide effect, it can be easily obtained by performing a measurement in an anechoic room where a sound is emitted from a speaker of a mobile phone and simultaneously collected by a microphone. Here, when the maximum volume is sounded from the speaker of the mobile phone, and at this time collected from the microphone and the noise level of P is obtained by the input volume detection unit 152,
It can be easily defined such that the noise level in the library is 40 + P decibels and the noise level in the city is 70 + P decibels.

(2) In the above embodiment, the left and right audio signals are mutually reduced to realize the wide effect. However, the present invention is not limited to this, and may be realized by other methods for increasing stereo feeling in stereo audio. Good. For example, the wide effect may be realized by performing addition, multiplication, subtraction, and the like on the left and right audio signals.
(3) Specifically, each of the above devices is a computer system including a microprocessor, a ROM, a RAM, a hard disk unit, a display unit, a keyboard, a mouse, and the like. A computer program is stored in the RAM or the hard disk unit. Each device achieves its function by the microprocessor operating according to the computer program. Here, the computer program is configured by combining a plurality of instruction codes indicating instructions for the computer in order to achieve a predetermined function.

(4) The present invention may be the method described above. Further, the present invention may be a computer program that realizes these methods by a computer, or may be a digital signal composed of the computer program.
The present invention also records the computer program or the digital signal on a computer-readable recording medium, such as a flexible disk, hard disk, CD-ROM, MO, DVD, DVD-ROM, DVD-RAM, semiconductor memory, etc. It is good also as what you did. Further, the present invention may be the computer program or the digital signal recorded on these recording media.

Further, the present invention may transmit the computer program or the digital signal via an electric communication line, a wireless or wired communication line, a network represented by the Internet, a data broadcast, or the like.
The present invention may be a computer system including a microprocessor and a memory, wherein the memory stores the computer program, and the microprocessor operates according to the computer program.

In addition, the program or the digital signal is recorded on the recording medium and transferred, or the program or the digital signal is transferred via the network or the like, and is executed by another independent computer system. It is good.
(5) The above embodiment and the above modifications may be combined.

  The cellular phone according to the present invention makes it easy for the user to listen to the stereo sound by appropriately controlling the wide effect of the stereo sound when the environmental sound such as noise is loud or the openable cellular phone is in the closed state. It is used as a communication terminal in a mobile phone network.

It is a front view of the mobile phone of the present invention. 1 is a side view of a mobile phone according to the present invention. It is a block diagram which shows the structure of the wide effect control part of the mobile telephone which concerns on this invention. It is a flowchart which shows a wide effect control process. It is a figure which shows the mixing ratio used in each state of an open state and a closed state. It is a block diagram which shows the structure of the wide effect control part which concerns on a modification.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 Mobile phone 101 Wide effect control part 102 Wide effect control part 120 Upper housing | casing 130 Lower housing | casing 110 Opening / closing detection part 131 AD conversion part 132 AD conversion part 133 Volume detection part 134 Phase difference detection part 135 Multiplier 136 Phase difference emphasis part 137 DA converter 138 DA converter 139 amplifier 140 amplifier 121 L speaker 122 R speaker 151 microphone 152 input sound volume detector

Claims (8)

A mobile phone that reproduces a stereo audio signal by applying a pseudo surround effect to the audio signal,
Output means for outputting a stereo audio signal to a speaker;
Determining means for determining whether or not to reduce the pseudo surround effect;
A phase difference emphasizing unit that outputs the stereo audio signal to the output unit by reducing the degree of enhancement of the phase difference between the left audio signal and the right audio signal when it is determined that reduction is necessary. Mobile phone. The mobile phone is openable,
The speaker is provided at a position exposed in the open state and inward in the closed state,
The mobile phone according to claim 1, wherein the determination unit determines whether or not the own device is in a closed state, and determines that the pseudo surround effect needs to be reduced when the device is in the closed state. The mobile phone according to claim 2, wherein the mobile phone is a foldable type and is closed when folded. 2. The mobile phone according to claim 1, wherein the determination unit receives an input of an environmental sound, determines whether or not the input sound volume is higher than a predetermined amount, and determines that it is necessary to reduce the pseudo surround effect when the input sound volume is high. Phone. The phase difference emphasizing means operates when it is determined that reduction is necessary,
A phase difference calculation unit for calculating a phase difference value between the left audio signal and the right audio signal;
A volume calculation unit for calculating a volume value of the stereo audio signal;
A multiplier that multiplies the calculated phase difference value by the volume value;
An emphasis unit that emphasizes the phase difference between the left audio signal and the right audio signal based on a predetermined enhancement degree according to the multiplication result value applied when it is determined that reduction is necessary;
The mobile phone according to claim 1, further comprising: an output unit that outputs the right and left audio signals with enhanced phase difference to the output unit. The enhancement degree corresponding to each multiplication result value less than the predetermined value is the same value,
The emphasis unit further includes:
The mobile phone according to claim 5, wherein when the multiplication result value is less than a predetermined value, the phase difference between the left audio signal and the right audio signal is emphasized based on the same value. . The degree of emphasis corresponding to each multiplication result value greater than or equal to a predetermined value decreases at a constant rate corresponding to the increase in the multiplication result value,
The emphasis unit further includes:
The phase difference between the left audio signal and the right audio signal is emphasized based on the enhancement degree corresponding to the multiplication result value when the multiplication result value is equal to or greater than a predetermined value. 5. The mobile phone according to 5. The emphasis part is
Based on a predetermined degree of enhancement according to the multiplication result value applied when it is determined that reduction is necessary,
From the left audio signal, subtract the signal obtained by multiplying the signal equivalent to the right audio signal by the enhancement degree,
The mobile phone according to claim 5, wherein a signal obtained by multiplying a signal corresponding to a left audio signal by the enhancement degree is subtracted from the right audio signal.

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