Method and electronic circuit for improving a driving force function of an electrodynamic acoustic transducer

Patent metadata

Field	Value
Publication number	US-11526645-B2
Application number	US-202016856016-A
Country	US
Kind code	B2
Filing date	Apr 22, 2020
Priority date	Apr 23, 2019
Publication date	Dec 13, 2022
Grant date	Dec 13, 2022

Abstract

Method and electronic circuit for determining a scaling factor k for a driving force function of a model of an electrodynamic acoustic transducer having at least two voice coils. Input signal fed into the transducer and it's model cause electromotive forces. A shift for the driving force function is determined on the base of the ratios between the real electromotive forces and the modeled electromotive forces. Finally, the scaling factor k is determined on the basis of a deviation between the real electromotive forces and the modeled electromotive forces at time points where the real electromotive forces and the modeled electromotive forces each are equal. The invention moreover relates to an electronic circuit for performing the above steps, and to a transducer system with the electronic circuit and a connected transducer.

First claim

What is claimed is:

1. A method of determining a scaling factor k for a modeled driving force function dependent on a membrane excursion of a model of an electrodynamic acoustic transducer having at least two voice coils, comprising the steps of:
a) applying a first input signal to at least one of the voice coils of the real electrodynamic acoustic transducer and applying a second input signal to the model of the electrodynamic acoustic transducer;
b) calculating a graph of a first electromotive force for a first voice coil of the at least two voice coils and a second electromotive force for a second voice coil of the at least two voice coils of the real electrodynamic acoustic transducer and calculating a graph of a first electromotive force for a first voice coil of the voice coils and a second electromotive force for a second voice coil of the voice coils of the model of the electrodynamic acoustic transducer;
c) shifting the modeled driving force function by modification of an excursion argument until a deviation between a ratio between the first electromotive force and the second electromotive force of the real electrodynamic acoustic transducer and the ratio between the first electromotive force and the second electromotive force of the model of the electrodynamic acoustic transducer is below a predetermined threshold;
d) finding/selecting a first time point where the first electromotive force substantially equals the second electromotive force of the real electrodynamic acoustic transducer and finding/selecting a second time point where the first electromotive force substantially equals the second electromotive force of the model of the electrodynamic acoustic transducer with the shifted modeled driving force function;
e) determining the scaling factor k for the shifted modeled driving force function by use of a deviation of the electromotive forces originating from the real electrodynamic acoustic transducer at said first time point or in a time span including said first time point from the electromotive forces originating from the model of the electrodynamic acoustic transducer at said second time point or in a time span including said second time point; and
f) updating the modeled driving force function by multiplying the modeled driving force function with the scaling factor k.

2. The method as claimed in claim 1 , characterized in that the first input signal and/or the second input signal is a sine signal with constant magnitude in step a).

3. The method as claimed in claim 1 , characterized in that the first input signal and/or the second input signal is a sine signal with a varying magnitude.

4. The method as claimed in claim 1 , characterized in that the first input signal and/or the second input signal is a noise signal in step a).

5. The method as claimed in claim 1 , characterized in that the first input signal and/or the second input signal has only frequency components above 0.95 times the resonant frequency of the electrodynamic acoustic transducer.

6. The method as claimed in claim 1 , characterized in that the first input signal and/or the second input signal has only frequency components below 0.95 times the resonant frequency of the electrodynamic acoustic transducer.

7. The method as claimed in claim 1 , characterized in that a frequency of the first input signal and/or a frequency of the second input signal substantially equals the resonant frequency of the electrodynamic acoustic transducer.

8. The method as claimed in claim 1 , characterized in that the first input signal and the second input signal have the same frequency or frequency components.

9. The method as claimed in claim 1 , characterized in that the first input signal and the second input signal are identical.

10. The method as claimed in claim 1 , characterized in that the electromotive force of the first coil of the real electrodynamic acoustic transducer (U emf1 ) and the electromotive force of the second coil of the real electrodynamic acoustic transducer (U emf2 ) are calculated by the formulas
U emf1 =U in1 −R DC1 ·I in
U emf2 =U in2 −R DC2 *I in
in step b) wherein R DC1 is a coil resistance of the first coil of the real electrodynamic acoustic transducer, U in1 is an input voltage to the first coil of the real electrodynamic acoustic transducer and I in is an input current to the first coil of the real electrodynamic acoustic transducer, and R DC2 is a coil resistance of the second coil of the real electrodynamic acoustic transducer, U in2 is an input voltage to the second coil of the real electrodynamic acoustic transducer and I in is an input current to the second coil of the real electrodynamic acoustic transducer.

11. The method as claimed in claim 1 , characterized in that the electromotive force of the first coil of the modeled electrodynamic acoustic transducer (U emf1 ′) and the electromotive force of the second coil of the modeled electrodynamic acoustic transducer (U emf2 ′) are calculated by the formulas
x ( t )= A ·sin(ω t )

v ( t )= A ·ω·cos(ω t )

U emf1,2 ′=BL ( x ( t ))· A ·ω·cos(ω t )

U emf1,2 ′=BL ( A ·sin(ω t ))· A ·ω·cos(ω t )

wherein x(t) is the membrane excursion of a modeled membrane, A is an amplitude of the modeled membrane, ω is a frequency of the second input signal, t is a time, and v(t) is an actual velocity of the modeled membrane.

12. The method as claimed in claim 1 , characterized in that a shift for the modeled driving force function being dependent on the membrane excursion is determined by use of a root mean square value of the electromotive forces originating from the real electrodynamic acoustic transducer and of a root mean square value of the electromotive forces originating from the model of the electrodynamic acoustic transducer in step c).

13. The method as claimed in claim 12 , characterized in that the modeled driving force function is shifted by the shift until a ratio between the root mean square value of the first electromotive force or the rectified low pass filtered first electromotive force and the root mean square value of the second electromotive force or the rectified low pass filtered second electromotive force originating from the real electrodynamic acoustic transducer substantially equals said ratio for the electromotive forces originating from the model of the electrodynamic acoustic transducer in step c).

14. The method as claimed in claim 1 , characterized in that a shift for modeled driving force function being dependent on the membrane excursion is determined by use of a rectified and low pass filtered graph of the electromotive forces originating from the real electrodynamic acoustic transducer and of a rectified and low pass filtered graph of the electromotive forces originating from the model of the electrodynamic acoustic transducer in step c).

15. The method as claimed in claim 14 , characterized in that a cut off frequency of a low pass used for low pass filtering the graph of the electromotive forces originating from the real electrodynamic acoustic transducer and the graph of the electromotive forces originating from the model of the electrodynamic acoustic transducer is below a lower cutoff frequency of a frequency range of the real electrodynamic acoustic transducer.

16. The method as claimed in claim 1 , characterized in that a graph of a difference of the first electromotive force and the second electromotive force for the real electrodynamic acoustic transducer is calculated and the first time point is selected in the graph of said difference where sa

Assignees

• Sound Solutions Int Co Ltd

Inventors

• Reining Friedrich

Classifications

• H04R9/04

  Construction, mounting, or centering of coil · CPC title

• G06F30/373 Primary

  Design optimisation · CPC title

• H04R9/18

  Resonant transducers, i.e. adapted to produce maximum output at a predetermined frequency · CPC title

• H04R9/025

  Magnetic circuit · CPC title

• G06F30/367 Primary

  Design verification, e.g. using simulation, simulation program with integrated circuit emphasis [SPICE], direct methods or relaxation methods · CPC title