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EP-3863301-B1 - ELECTROSTATIC ELECTROACOUSTIC TRANSDUCER DEVICE, SIGNAL PROCESSING CIRCUIT FOR ELECTROSTATIC ELECTROACOUSTIC TRANSDUCER, SIGNAL PROCESSING METHOD, AND SIGNAL PROCESSING PROGRAM

EP3863301B1EP 3863301 B1EP3863301 B1EP 3863301B1EP-3863301-B1

Inventors

  • IRII, KOICHI
  • AKINO, HIROSHI

Dates

Publication Date
20260513
Application Date
20190905

Claims (14)

  1. A signal processing circuit (12) for an electrostatic electroacoustic transducer (15) configured to correct signals input to a single driven electrostatic electroacoustic transducer (15) including a diaphragm (151) and a fixed electrode (152) disposed to face the diaphragm (151), the signal processing circuit (12) comprising: a correction value determiner (122) configured to determine a correction value (v1) based on a level (L) of an input signal (s1) from a sound source (S); and a level corrector (124) configured to correct the level (L) of the input signal (s1) based on the correction value (v1), wherein the level corrector (124) is configured to correct the level (L) of the input signal (s1) using the correction value (v1) only when the input signal (s1) corresponds to when the input signal (s1) displaces the diaphragm (151) in a first direction towards a side on which the fixed electrode (152) is not disposed with respect to a predetermined position, the level corrector (124) does not correct the level (L) of the input signal (s1) when the input signal (s1) displaces the diaphragm (151) to a second direction side on which the fixed electrode (152) is disposed with respect to the predetermined position, and the predetermined position is a non-vibrating position of the diaphragm (151).
  2. The signal processing circuit (12) for the electrostatic electroacoustic transducer (15) according to claim 1, wherein the level corrector (124) is configured to increase the level (L).
  3. The signal processing circuit (12) for the electrostatic electroacoustic transducer (15) according to claim 1, wherein the correction value (v1) is a value for displacing the diaphragm (151) by a required amount of displacement in the first direction.
  4. The signal processing circuit (12) for the electrostatic electroacoustic transducer (15) according to claim 1, further comprising: a level detector (121) configured to detect the level (L) of the input signal (s1), wherein the correction value determiner (122) is configured to determine the correction value (v1) based on the level (L) detected by the level detector (121).
  5. The signal processing circuit (12) for the electrostatic electroacoustic transducer (15) according to claim 4, further comprising: a storage (123) configured to store a plurality of parameters (Pr) corresponding to a plurality of levels (L) of the signals, wherein the correction value determiner (122) is configured to select a parameter (Pr) from the plurality of parameters (Pr) based on the level (L) detected by the level detector (121) and to output the selected parameter (Pr) as the correction value (v1) to the level corrector (124).
  6. The signal processing circuit (12) for the electrostatic electroacoustic transducer (15) according to claim 5, wherein each parameter (Pr) corresponds to a respective range of the level (L).
  7. The signal processing circuit (12) for the electrostatic electroacoustic transducer (15) according to claim 5, wherein the storage (123) is configured to store parameter groups composed of a plurality of parameters (Pr), the parameter groups include a first parameter group and a second parameter group, and a plurality of parameters (Pr) constituting the first parameter group are different from a plurality of parameters (Pr) constituting the second parameter group.
  8. The signal processing circuit (12) for the electrostatic electroacoustic transducer (15) according to claim 4, wherein the correction value determiner (122) is configured to calculate the correction value (v1) based on the level (L) detected by the level detector (121).
  9. The signal processing circuit (12) for the electrostatic electroacoustic transducer (15) according to claim 8, further comprising: a storage (123) configured to store a calculation function determined in accordance with the electrostatic electroacoustic transducer (15), wherein the correction value determiner (122) is configured to calculate the correction value (v1) based on the calculation function.
  10. The signal processing circuit (12) for the electrostatic electroacoustic transducer (15) according to claim 9, wherein the calculation function is a polynomial approximating a measured value of the correction value (v1), and the correction value determiner (122) is configured to calculate the correction value (v1) using the polynomial.
  11. The signal processing circuit (12) for the electrostatic electroacoustic transducer (15) according to claim 9, wherein the storage (123) is configured to store a plurality of calculation functions corresponding to an amount for correcting the level (L).
  12. An electrostatic electroacoustic transducer device (100), comprising: a single driven electrostatic electroacoustic transducer (15) including a diaphragm (151) and a fixed electrode (152) disposed to face the diaphragm (151); and the signal processing circuit (12) of claim 1.
  13. A signal processing method executed by a signal processing circuit (12) configured to correct signals input to a single driven electrostatic electroacoustic transducer (15) comprising a diaphragm (151) and a fixed electrode (152) disposed to face the diaphragm (151), the signal processing method including: determining a correction value (v1) based on a level (L) of an input signal (s1) from a sound source (S); and correcting the level (L) of the input signal (s1) based on the correction value (v1), wherein correcting corrects the level (L) of the input signal (s1) using the correction value (v1) only when the input signal (s1) corresponds to when the input signal (s1) displaces the diaphragm (151) in a first direction towards a side on which the fixed electrode (152) is not disposed with respect to a predetermined position, correcting does not correct the level (L) of the input signal (s1) when the input signal (s1) displaces the diaphragm (151) to a second direction side on which the fixed electrode (152) is disposed with respect to the predetermined position, and the predetermined position is a non-vibrating position of the diaphragm (151).
  14. A signal processing program which, when executed by a signal processing circuit (12) of claim 1, causes the signal processing circuit to perform the signal processing method of claim 13.

Description

TECHNICAL FIELD The present invention relates to an electrostatic electroacoustic transducer device, a signal processing circuit for an electrostatic electroacoustic transducer, a signal processing method, and a signal processing program. The present invention particularly relates to a driving circuit of a single driven electrostatic electroacoustic transducer including a fixed electrode disposed to face a surface of a diaphragm. BACKGROUND ART An electroacoustic transducer converts vibration of air (sound) into an electrical signal, or an electrical signal into vibration of air (sound). Types of the electroacoustic transducer include an electrostatic (condenser type) electroacoustic transducer. The electrostatic electroacoustic transducer includes a diaphragm and a fixed electrode disposed to face the diaphragm. The electrostatic electroacoustic transducer utilizes an electrostatic capacitance between the diaphragm and the fixed electrode or the electrostatic force acting between the diaphragm and the fixed electrode. Therefore, the electrostatic electroacoustic transducer requires a voltage (polarization voltage) to provide a potential difference between the diaphragm and the fixed electrode. Electrostatic electroacoustic transducers are divided into two types according to a method of adding polarization voltage: a pure condenser type electrostatic electroacoustic transducer and an electret type electrostatic electroacoustic transducer. The pure condenser type electrostatic electroacoustic transducer applies DC voltage (polarization voltage) from an external power supply (polarization power supply) between the diaphragm and the fixed electrode. The electret type electrostatic electroacoustic transducer applies DC voltage (polarization voltage) between the diaphragm and the fixed electrode by holding a charge on the diaphragm or the fixed electrode. Further, electrostatic electroacoustic transducers are divided into two types according to an arrangement of the fixed electrode: a single driven electrostatic electroacoustic transducer and a push-pull driven electrostatic electroacoustic transducer. In the single driven electrostatic electroacoustic transducer, the fixed electrode is arranged to face a surface of the diaphragm. On the other hand, in the push-pull driven electrostatic electroacoustic transducer, two fixed electrodes are arranged to face both surfaces of the diaphragm with the diaphragm therebetween. Examples of an audio equipment that converts an electric signal to vibration of air (emitting sound) using such electrostatic electroacoustic transducer include a condenser-type speaker and a condenser-type headphone (earphone). FIG. 1 is a schematic cross-sectional view illustrating a basic configuration of a conventional single driven electrostatic electroacoustic transducer. The single driven electrostatic electroacoustic transducer includes a diaphragm 1, a fixed electrode 2 having a plurality of openings 2a, and a spacer 3. The fixed electrode 2 is disposed to face a surface of the diaphragm 1 through the spacer 3. A signal voltage 4 is supplied between a conductive film (not illustrated) formed on the diaphragm 1 and the fixed electrode 2. FIG. 2 is a schematic cross-sectional view illustrating a basic configuration of a conventional push-pull driven electrostatic electroacoustic transducer. The push-pull driven electrostatic electroacoustic transducer includes a diaphragm 1, two fixed electrodes 2 having a plurality of openings 2a, and two spacers 3. Each of the two fixed electrodes 2 are disposed to face a front surface and a rear surface of the diaphragm 1, respectively, through a spacer 3. A signal voltage 4 is supplied between both fixed electrodes 2. As described above, in the electrostatic electroacoustic transducer that converts the electric signal into the vibration of air, the diaphragm 1 vibrates by an electrostatic force acting between the diaphragm 1 and the fixed electrode 2. That is, the diaphragm 1 is displaced in a direction (first direction) in which the fixed electrode 2 is not disposed by being repelled to the fixed electrode 2 when a charge having the same polarity as the charge held by the fixed electrode 2 is applied. On the other hand, the diaphragm 1 is displaced in a direction (second direction) in which the fixed electrode 2 is disposed by being attracted to the fixed electrode 2 when a charge having a polarity opposite to the charge held by the fixed electrode 2 is applied. The electrostatic force acting between the diaphragm 1 and the fixed electrode 2 is inversely proportional to a square of the distance between the diaphragm 1 and the fixed electrode 2. Therefore, in the single driven electrostatic electroacoustic transducer illustrated in Fig. 1, when the diaphragm 1 is displaced in the first direction, the electrostatic force becomes weaker as the diaphragm 1 moves away from the fixed electrode 2. On the other hand, when the diaphragm 1 is displaced in the sec