JP2012015717A - Speaker driving control system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To control driving of an electronic device speaker.SOLUTION: The speaker driving control system comprises: measuring means for measuring immittance of a speaker 47; determination means for determining whether water is entering from a sound hole of the speaker 47 based on the results measured by the measuring means; and switching means for switching gain for a signal that sounds the speaker 47 to another setting when the measuring means determine that the water is entering.

Description

  The present invention relates to a speaker drive control system. In particular, the present invention relates to a speaker drive control system that controls driving of a speaker of an electronic device.

  Many electronic devices such as a mobile phone equipped with a speaker are provided with a waterproof mechanism so that water does not enter the electrical circuit portion of the speaker even if the electronic device is submerged or wet with water (for example, Patent Document 1). reference.). As the waterproof mechanism, for example, it is conceivable to provide a waterproof film between the speaker and the sound hole of the housing, or to perform waterproofing on the vibration film itself of the speaker. In an electronic device provided with such a waterproof mechanism, the speaker and the circuit that electrically drives the speaker are not damaged even if the electronic device is submerged or wet. However, when submerged or wet, water enters from the sound hole of the speaker, and the acoustic characteristics of the speaker change.

  As an example of the waterproof mechanism, it is conceivable that the speaker diaphragm is waterproofed or the diaphragm is made of a highly waterproof material. However, in that case, the mechanical compliance (stiffness), mass, and mechanical viscosity of the vibration membrane change due to water adhering to the vibration membrane of the speaker.

  In addition, if a waterproof mechanism is realized by sticking a waterproof film between the speaker and the electronic device terminal case, the acoustic compliance, acoustic inertance, Air friction changes.

  FIG. 14 shows the presence / absence of water, that is, changes in the sound pressure frequency characteristics (distance 10 cm from the speaker sound hole 3) of the speaker before and immediately after the mobile phone gets wet. 20 is a sound pressure frequency characteristic when the terminal is completely wet before or after the terminal is wet, and 21 is a sound pressure frequency characteristic when water is present immediately after the terminal is wet. is there.

JP 2004-056165 A

  As described above, when an electronic device such as a mobile phone gets wet with water, the sound pressure of the speaker is greatly reduced. As a result, the user of the electronic device has a problem in use. For example, as a case where such a problem occurs, there may be a situation where a mobile phone having a waterproof function is brought into a bathroom or the like and a speaker is sounded.

  In order to solve the above-described problem, according to the first aspect of the present invention, there is provided a speaker drive control system for controlling the drive of a speaker of an electronic device, the measurement means for measuring the immittance of the speaker, and the measurement means Based on the measurement results, a determination means for determining whether water has entered from the sound hole of the speaker, and a gain for a signal for causing the speaker to ring when the determination means determines that water has entered. Switching means for switching to another setting.

  In addition, as described above, the summary of the invention does not enumerate all necessary features of the present invention, and sub-combinations of these feature groups can also be the invention.

  As is apparent from the above description, in the present invention, even if water enters the housing from the sound hole of the speaker of the electronic device, a speaker ringing sound with a constant sound pressure and sound quality is always output. be able to.

It is a figure which shows an example of the mobile telephone 1 which concerns on one Embodiment. It is a figure which shows an example of the waterproofing mechanism of the speaker which concerns on one Embodiment. It is a figure which shows the electrical, mechanical, and acoustic impedance concentrated circuit of the impedance of a dynamic type speaker. It is a figure which shows acoustic impedance. An example of the utilization environment of the speaker drive control system which concerns on one Embodiment is shown. It is a figure which shows the example of a measurement result of a pure resistance component (resistance) among the impedances of a speaker. It is a figure which shows the determination flowchart of the presence or absence of water permeation. It is a figure which shows the frequency characteristic of an equalizer when water infiltrates into a speaker sound hole. It is a figure which shows the change before and behind water penetrate | invades into a speaker sound hole about reactance. An example of the utilization environment of the speaker drive control system which concerns on another embodiment is shown. An example of a use environment of a speaker drive control system according to another embodiment will be described. It is a figure for demonstrating the setting of an equalizer. It is a figure for demonstrating the setting of an equalizer. It is a figure which shows the presence or absence of water, ie, the change of the sound pressure frequency characteristic (distance 10 cm from speaker sound hole 3) of the speaker before a mobile phone gets wet with water and immediately after getting wet.

  Hereinafter, the present invention will be described through embodiments of the invention. However, the following embodiments do not limit the invention according to the scope of claims, and are combinations of features described in the embodiments. Not all are essential to the solution of the invention.

  FIG. 1 shows an example of a mobile phone 1 according to an embodiment. The mobile phone 1 is a portable phone using wireless communication. The mobile phone 1 includes a speaker 2, a sound hole 3, a display 4, and a key 5.

  The speaker 2 is a machine that generates electric sounds such as music and voice by changing electrical signals into physical vibrations. The speaker 2 is provided inside the housing 6 of the mobile phone 1. The sound hole 3 is a hole for emitting sound generated by the speaker 2 to the outside of the housing 6 of the mobile phone 1. The sound hole 3 is provided in the housing 6 of the mobile phone 1 at a position where the diaphragm of the speaker 2 is located. The display 4 is for displaying characters and figures. Key 5 is for inputting a character by pressing a button with a finger.

  FIG. 2 shows an example of a waterproofing mechanism for a speaker according to an embodiment. In this embodiment, a dynamic speaker 10 will be described as an example of a speaker. The dynamic speaker 10 includes a diaphragm 14, a voice coil 15, a permanent magnet 16, and a yoke 17. Each of these parts is stored in a resin casing 11. A protector 12 is attached to one surface of the housing 11. The protector 12 is for preventing a large foreign matter from entering the sound emission direction. The protector 12 is often made of metal in order to maintain the mechanical strength of the entire speaker. The protector 12 is provided with a sound hole 13 for emitting sound generated from the dynamic speaker 10 to the outside of the housing 11 of the dynamic speaker 10. In addition, a sound hole 19 for emitting a sound having a phase opposite to that of the sound emitted from the sound hole 3 is provided on the rear surface of the housing 11. Note that the sound emitted through the back sound hole 19 is radiated to the back volume in the housing 6, but the terminal housing is almost sealed, and the radiation of this sound wave to the outside of the terminal housing is small. Suppose that consideration is given so as not to cancel out the sound wave from the radiation sound hole 3.

  The vibration film 14 is made of a resin material having a low mass density and low mechanical compliance. The voice coil 15 drives the vibration film 14. The permanent magnet 16 and the yoke 17 constitute a magnetic circuit.

  The dynamic speaker 10 having such a configuration is attached to a position corresponding to the sound hole 3 provided in the housing 6 of the mobile phone 1. Specifically, the dynamic speaker 10 is attached to a rib 7 formed inside the housing 6 by a double-sided tape 8. At that time, a waterproof sheet 9 is provided between the dynamic speaker 10 and the rib 7. The waterproof sheet 9 is for preventing the water 18 from entering the housing 11 of the dynamic speaker 10 and the housing 6 of the mobile phone 1. The dynamic speaker 10 may be waterproofed by using the vibrating membrane 14 instead of the waterproof sheet 9 to prevent water from entering the speaker.

FIG. 3 shows a lumped circuit of the electrical, mechanical and acoustic impedances of the dynamic speaker impedance. The impedance of the speaker consists of static impedance and dynamic impedance, and the dynamic speaker consists of a magnetic circuit consisting of a voice coil, permanent magnet and yoke, so the static impedance consists of resistance (pure resistance) and reactance. ing. 22 is an input voltage signal E (V) to the speaker, 23 is an electrical inductance L _s (H) of the voice coil, 24 is an electrical pure resistance (resistance) R _s (Ω) of the voice coil, 25 is an electro-mechanical A transformer representing a conversion unit, A is called an electromechanical coupling coefficient, and voltage AV (V) is applied to this transformer. Further, the current flowing from 22 to 24 is I (A). 26 is the mass of the voice coil and diaphragm of 14 and 15 in FIG. 2, that is, the dynamic speaker, and can be expressed as an inductance L _m (H) when described by an electrical analogy equivalent circuit. Reference numeral 27 denotes mechanical viscosity, which is mainly present in the vibration film 14. Reference numeral 28 denotes stiffness (mechanical compliance), which also exists in the vibration film 14, and can be described as capacitance in an electrical analog equivalent circuit, and is C _m (F). 29 is obtained by multiplying the acoustic impedance Z _acoustic by the square of the area S (m ² ) of the diaphragm and converting it to mechanical impedance. When the resistance of the voice coil is R (Ω), the self-inductance is L (H), and each frequency of the electric signal is ω (rad / s), the total static impedance Z _static is given by the following equation (1).

On the other hand, dynamic impedance is not electrical or static impedance, but is originally mechanical impedance generated due to mechanical vibration of the voice coil, diaphragm connected to it, and the entire speaker. It is an impedance component that is electrically added to the equation (1) by being converted into an electrical impedance by electro-mechanical coupling. This dynamic impedance is represented by the following formula (2) using the mechanical resistance r _m , the mass m, and the mechanical compliance C _m as described below.

  In FIG. 3, E (V) is the input voltage to the speaker, I (A) is the current flowing through the voice coil of the speaker, and V (m / s) is the vibration speed of the voice coil. A is an electromechanical conversion rate. For a dynamic speaker, if a magnetic flux density B (T) penetrating a voice coil by a permanent magnet and a total length l (m) of the voice coil 15 are obtained, Equation (3) is obtained.

As described above, when Z _static , E, l, V, and A are combined into a voltage balanced equation on the primary side of the transformer (electrical to mechanical conversion) as described above, the following equation (4) is obtained.

  Further, when the equilibrium equation is written on the secondary side, it can be expressed as equation (5).

FIG. 4 shows the acoustic impedance. When the entire acoustic impedance shown in FIG. 4 is expressed as Z _acoustic, and the area of the speaker diaphragm is S, the conversion of the acoustic impedance and the mechanical impedance is converted by using the square of the area S as a conversion coefficient. Becomes S ² Z _acoustic . In FIG. 4, 30 is the acoustic compliance C _ab (F) with respect to the back volume in the terminal housing outside the speaker housing, 31 is the pressure P (Pa) obtained from the vibrating membrane, 32, 33 and 34 are the waterproof membrane 9 respectively. _Are acoustic compliance C _{a_sheet} (F), acoustic inertance L _{a_sheet} (F), and acoustic resistance R _{a_sheet} (Ω). 35 is the acoustic compliance C _af (F) due to the space between the sound hole 13 of the speaker housing and the sound hole 3 of the terminal housing (the volume of the front air chamber), and 36 and 37 are the sound sound holes of FIG. 3 is an acoustic inertance L _af (H) and an acoustic resistance R _af (Ω). Sound inertance and acoustic resistance are also generated by the sound hole 13 of the speaker housing, but this is very small compared to L _af (H) and R _af (Ω) (because the sound hole area is designed to be large). ) And may be ignored as a result. Reference numeral 38 denotes a radiation impedance Z _r (Ω) in the sound hole 3 of the housing, which is described as the following formula (6).

If the impedance from 32 to 37 of the impedance in the radiated sound direction of the acoustic (analogous) equivalent circuit shown in FIG. 4 is collectively represented as Z _f (Ω), the balanced equation of this acoustic equivalent circuit is the following formula ( 7) It becomes as follows.

Further, the radiation impedance Z _r flows into (and circuit representation) volume velocity U _out can be described as following equation with respect to the total volume velocity U through this entire acoustic equivalent circuit (8).

Therefore, as the absolute value of Z _f is small, the radiation impedance Z _r flows into (and circuit representation) volume velocity U _out is increased, since a large acoustic energy is radiated from the speaker, the volume of auditory user The sound pressure almost proportional to (sense amount) also increases. According to the equations (4), (5), (7), and (8), the electro-mechanical-acoustic system is all connected, and the change in the acoustic impedance becomes the change in the acoustic load Z _acoustic , -Since all the sound is connected, it has been shown to appear as a change in the dynamic component of the electrical impedance.

  FIG. 5 shows an example of a use environment of the speaker drive control system according to the embodiment. 39 is a sound source signal and 40 is an equalizer, which is realized by a DSP, FPGA, or the like. 40 is set so as to switch its parameter in response to a detection signal that water 46 and 42 described later have entered. Reference numeral 41 denotes a digital gain that increases or decreases the overall level of the digital signal, and may be included in the acoustic signal processing unit 40. Similarly to 40, a parameter for receiving a detection signal that water 46 and 42 described below has entered the parameter is received. Is set to switch. A detection unit 43 detects whether or not water has entered the speaker sound hole, and determines whether water has entered the sound hole in response to a signal from a speaker impedance detector 46 described later. . 43 is a D / A converter that converts a digital signal to an analog signal, 44 is an analog gain that increases or decreases the level of the entire analog signal, 45 is an audio amplifier that drives the speaker, and 46 is an impedance measuring instrument that measures the impedance of the speaker. It is.

FIG. 6 shows an example of an actual measurement result of the pure resistance component (resistance) in the impedance of the speaker. 48 is a resistance at the normal time (when water does not enter the speaker sound hole), and 49 is a resistance when water is infiltrated. 48 has a peak in the vicinity of 1100 Hz (referred to as a basic resonance frequency f0), whereas 49 has an effect that water has entered the speaker sound hole, and f0 has decreased to about 850 Hz. In addition, the sharpness (Q value) of f0 is decreased. These are the real parts of the mechanical load shown in the equation (9) excluding the acoustic load in the equation (5) because L _m , R _m and C _m of the mechanical impedance in FIG. This is because both the imaginary part increases and the LC resonance frequency decreases.

  In the present embodiment, the impedance measuring device 46 measures the frequency range (850 Hz to 1200 Hz) indicated by 50 in FIG. 6 and sends the measurement result to 42. The water intrusion presence / absence determination unit 42 determines that there is no water intrusion if impedance is recognized in the frame 51 of FIG. 6, and determines that water has intruded if not recognized. The measurement range 50 and the impedance confirmation region 51 of the f0 peak may be set in consideration of variations in characteristics of the electrical processing unit and the speaker in FIG.

  FIG. 7 shows a flow chart for determining whether water has entered. 52 is a flow chart for confirming the presence or absence of water intrusion, and 53 is a speaker impedance measurement and a water intrusion confirmation. Reference numeral 54 denotes a process in the case where it is determined that water has not entered, and is a process for causing the speaker to ring with the normal equalizer 40 and digital gain 41 parameters. 55 is a process in the case where it is determined that water has entered, and when the water has entered, the values of the equalizer 40 and the digital gain 41 are set so that the sound pressure and sound quality of the speaker can be properly maintained. Performs processing to ring. In addition, from 54 and 55, by performing loop processing to return to the impedance measurement of 53 speakers and the presence or absence of water intrusion every certain time, water entered the speaker sound hole during ringing. Even in this case, it is possible to move to 55 processing. Reference numeral 56 denotes a final process in which the user finishes ringing.

  FIG. 8 shows the frequency characteristics of the equalizer when water enters the speaker sound hole. 56 is an equalizer setting when water is not intruding, and is a setting that is flat and has no gain over the entire band. 57 is an equalizer characteristic at the time of water ingress. Since the sound pressure in the high range is reduced by about 10 dB, the setting is made to correct. In the present embodiment, an example in which the equalizer value is changed is shown in FIG. 8, but it is also possible to perform a process of uniformly boosting the entire band with a digital gain.

  The present invention can be used for a receiver as well. The present invention can also be used for piezoelectric speakers and piezoelectric receivers.

  FIG. 9 shows changes in reactance before and after water enters the speaker sound hole. The present invention can also be realized by measuring the reactance component of the impedance components of the speaker with the impedance measuring device 46. The reactance peak value is 850 Hz when water does not enter, whereas it is about 700 Hz when water enters. The measurement range 60 and the target reactance value frame 61 may be set in consideration of variations in characteristics of the electrical processing unit and the speaker.

  FIG. 10 shows an example of a use environment of a speaker drive control system according to another embodiment. In the present invention, the analog gain can be adjusted when water intrusion is detected.

  FIG. 11 shows an example of a use environment of a speaker drive control system according to still another embodiment. In the present invention, it is possible to use an admittance measuring device instead of an impedance measuring device.

  In the present invention, the impedance or admittance measurement is not limited to the vicinity of the resonance frequency as shown in FIGS. 6 and 9, but is performed in a human audible band or a wide frequency band, and water enters the speaker sound hole. It is also possible to determine whether or not.

  In the present invention, 62 limiters / compressors can be arranged in order to avoid digital clipping of signals when boosting a part of the frequency band or the whole with the equalizer 40 and the digital gain 41 as shown in FIG. It is.

  In the present invention, as shown in FIGS. 12 and 13, the setting of the equalizer 40 can be set not only in one stage but in a plurality of stages, and it is possible to select which setting is set according to the impedance measurement result. In FIG. 12, reference numeral 63 denotes a region where five impedance detection ranges are provided, and each corresponds to 64 equalizer settings 1 to 5. FIG. 13 is provided with equalizer gains set for the equalizer settings 1 to 5, and from the top, the equalizer settings are 5, 4, 3, 2, 1. (The lower the impedance level is, the higher gain is set to give high gain.)

  As mentioned above, although this invention was demonstrated using embodiment, the technical scope of this invention is not limited to the range as described in the said embodiment. It will be apparent to those skilled in the art that various modifications or improvements can be added to the above embodiment. It is apparent from the scope of the claims that the embodiments added with such changes or improvements can be included in the technical scope of the present invention.

39 Sound source signal 40 Equalizer 41 Digital gain 42 Detector 43 D / A converter 44 Analog gain 45 Audio amplifier 46 Impedance measuring instrument 47 Speaker

Claims (4)

A speaker driving control system for controlling driving of a speaker of an electronic device,
Measuring means for measuring the immittance of the speaker;
Based on the measurement result measured by the measurement unit, a determination unit that determines whether water has entered from the sound hole of the speaker;
A speaker drive control system comprising: switching means for switching a gain for a signal for ringing the speaker to another setting when the determination means determines that water has entered. The speaker drive control system according to claim 1, wherein the measurement unit measures immittance of the speaker in a frequency band near the resonance frequency of the speaker. The speaker drive control system according to claim 1, wherein the measurement unit measures immittance of the speaker in a human audible band. The speaker drive control system according to claim 1, wherein the measurement unit measures immittance of the speaker in the entire use band of the speaker.

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