Receiver unit with enhanced frequency response

Abstract

The present invention relates to a receiver unit comprising a plurality of moveable membranes, a motor assembly being adapted to drive a first moveable membrane and one or more successive moveable membranes in accordance with an incoming electrical drive signal, wherein the first and at least one of the successive moveable membranes have different frequency responses in order to enhance the frequency response of the receiver unit. The present invention further relates to a hearing aid instrument comprising the receiver unit.

Claims

1. A receiver unit comprising: a) a plurality of moveable membranes, b) a motor being adapted to mechanically drive each of a first moveable membrane and one or more successive moveable membranes in accordance with an incoming electrical drive signal to the motor, wherein the first and at least one of the successive moveable membranes have different frequency responses.

2. A receiver unit according to claim 1, wherein the motor comprises a moving armature type motor, such as a balanced moving armature type motor.

3. A receiver unit according to claim 2, wherein the armature type motor includes an armature driving each of the first moveable membrane and at least one of the successive moveable membranes.

4. A receiver unit according to claim 1, wherein the motor is mechanically connected to each of the first and at least one of the successive membranes via a resonating element, such as a spring.

5. A receiver unit according to claim 4, wherein the first and/or at least one of the successive membranes comprise a resonating element.

6. A receiver unit according to claim 5, wherein a mechanical connection between the motor and the first and/or at least one of the successive membranes comprise a resonating element.

7. A receiver unit according to claim 1, wherein an acoustical back volume is associated with each of the respective first and at least one of the successive moveable membranes.

8. A receiver unit according to claim 1, wherein a combined acoustical back volume is formed by a combination of two or more acoustical back volumes, and wherein the motor is positioned within said combined acoustical back volume.

9. A receiver unit according to claim 8, wherein each of the combined acoustical back volumes comprises one or more acoustical openings.

10. A receiver unit according to claim 9, wherein the one or more acoustical openings are acoustically connected to one or more acoustical filters.

11. A receiver unit according to claim 1, wherein an acoustical front volume is associated with each of the first and successive moveable membranes.

12. A receiver unit according to claim 11, wherein a combined acoustical front volume is formed by a combination of two or more acoustical front volumes.

13. A receiver unit according to claim 12, wherein each of the combined acoustical front volumes comprises one or more acoustical openings.

14. A receiver unit according to claim 13, wherein the one or more acoustical openings are acoustically connected to one or more acoustical filters.

15. A hearing aid instrument comprising a receiver unit according to claim 1.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The present invention will now be described in further details with reference to the accompanying figures, wherein

(2) FIG. 1 shows a cross-sectional view of a receiver unit having two membranes where the sound output is taken from the back volume,

(3) FIG. 2 shows a cross-sectional view of a receiver unit having two membranes where the sound output is taken from the front volumes,

(4) FIG. 3 shows simulated frequency response curves, and

(5) FIG. 4 shows measured frequency response curves.

(6) While the invention is susceptible to various modifications and alternative forms specific embodiments have been shown by way of examples in the drawings and will be described in details herein. It should be understood, however, that the invention is not intended to be limited to the particular forms disclosed. Rather, the invention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the appended claims.

DETAILED DESCRIPTION OF THE INVENTION

(7) In its broadest aspect the present invention relates to a receiver unit having an enhanced frequency response. The receiver unit of the present invention should be applicable for various types of hearing aid instruments, including the MC where the available space for the receiver unit is very limited.

(8) Referring now to FIG. 1, a balanced armature receiver unit 100 is depicted. As seen in FIG. 1 the receiver unit 100 comprises a first moveable membrane 101 and a second (successive) moveable membrane 102 where the latter is responsible for the enhanced acoustic output. The first moveable membrane 101 and second moveable membrane 102 are driven by the same motor assembly 103, which is mechanically connected to both the first moveable membrane 101 and second moveable membrane 102. The motor assembly 103 may be an armature type motor.

(9) As illustrated in FIG. 1, a substantially stiff mechanical connection 104 is connecting the motor assembly 103 and the first membrane 101 via the resonating connection 111 which forms part of the first membrane 101. Contrary to this, a resonating mechanical connection 105 is connecting the motor assembly 103 and the second membrane 102.

(10) The mechanical connections 104 and 105 are both secured to a distal and moveable end of the motor drive pin 106. The movements of the drive pin 106 are indicated by the arrow. In case of a moving armature type motor, the drive pin 106 will be the moving armature that is hinged at an end being opposite to the distal and moveable end. A moving armature may take different shapes, such as a linear structure or for example a U-shaped armature structure.

(11) The resonating element 105, in combination with the mass of the second membrane 102, causes the second membrane 102 to resonate at a different frequency compared to the first membrane 101. This different frequency may either lower or higher that the resonance frequency of the first membrane.

(12) The drive pin 106 is brought into movements by applying an audio drive signal. The audio drive signal may be of various types, such as analog signals, pulse width modulated (PWM) signals etc.

(13) The first and second membranes 101, 102 are suspended in suspension members 107, 108 and 109, 110 respectively. As depicted in FIG. 1 the suspension members are positioned in opposite ends of the respective membranes 101, 102.

(14) As previously stated back and front volumes are defined as follows. (1) A back volume is located on that side of a membrane where the driving force is applied, i.e. typically on that side of the membrane where the motor assembly is positioned. (2) A front volume is located on the free side of a membrane, i.e. the side where the driving force is not applied.

(15) Still referring to FIG. 1, the receiver unit 100 comprises a combined back volume 112 and front volumes 113, 114. In receiver unit 100 depicted in FIG. 1, the sound outlet is taken from the back volume 112 via the acoustical opening 115. Other acoustical openings 116, 117 in the respective front volumes 113, 114 lead acoustical output signals to an acoustical filter unit 118 before the final signal 119 is generated.

(16) FIG. 2 shows a receiver unit 200 identical to the one depicted in FIG. 1. Thus, FIG. 2 shows a balanced armature receiver unit 200 is depicted comprising a first moveable membrane 201 and a second moveable membrane 202 being driven by the same motor assembly 203. Again, the motor assembly 203 may be an armature type motor. A substantially stiff mechanical connection 204 is connecting the motor assembly 203 and the first membrane 201 via the resonating connection 211 which forms part of the first membrane 201. Contrary to this a resonating mechanical connection 205 connects the motor assembly 203 and the second membrane 202. The mechanical connections 204 and 205 are both secured to a distal and moveable end of the motor drive pin 206 which in case of a moving armature type motor will be the moving armature. A moving armature may take different shapes, such as a linear structure or for example a U-shaped armature structure.

(17) The resonating element 205, in combination with the mass of the second membrane 202, causes the second membrane 202 to resonate at a different frequency compared to the first membrane 201. This different frequency may either lower or higher that the resonance frequency of the first membrane.

(18) The drive pin 206 is brought into movements by applying an audio drive signal. The audio drive signal may be of various types, such as analog signals, pulse width modulated (PWM) signals etc. The first and second membranes 201, 202 are suspended in suspension members 207, 208 and 209, 210, respectively, which are positioned in opposite ends of the respective membranes 201, 202.

(19) The receiver unit 200 comprises a combined back volume 212 and front volumes 213, 214. Contrary to the receiver unit 100 depicted in FIG. 1, the sound outlet is now taken from the front volumes 213, 214 via the acoustical openings 216, 217. Another acoustical opening 215 in the back volume 212 leads an acoustical output signal to an acoustical filter unit 218 before the final signal 219 is generated.

(20) FIGS. 3 and 4 show respective simulations and measurements of a receiver unit having an enhanced low-frequency response. The enhanced low-frequency responses are, for both simulations and measurements, compared to a single membrane receiver unit.

(21) FIG. 3 shows a simulation of the sound pressure level (SPL) vs. frequency for a single membrane balanced armature receiver 302 and a dual membrane balanced armature receiver 301. As seen in FIG. 3 the dual membrane receiver provides an enhanced SPL up to around 1 kHz. Above 1 kHz the SPL for the single and dual membrane receivers become essentially comparable. As seen from FIG. 3, the in-phase behaviour of the second membrane below its resonance frequency of around 350 Hz increases the overall SPL of the balanced armature receiver by around 10 dB from 10 Hz to 150 Hz. An even further enhancement of the SPL is provided around the resonance frequency (approximately 350 Hz) of the second membrane.

(22) FIG. 4 shows measured SPL's from a single membrane balanced armature receiver 402 and a dual membrane balanced armature receiver 401. The measured difference between single membrane 402 and dual membrane 401 receivers is not as pronounced as the simulated result presented in FIG. 3. However, the increased low-frequency SPL of the dual membrane receiver 401 is still evident in that an enhancement of up to 10 dB has been measured below the resonance frequency (around 620 Hz) of the second membrane.