Transducer Apparatus Having a Mechanical Acoustic Filter with Movable Blocking Member

1. An acoustic transducer comprising: a membrane, a back plate, where the membrane and the back plate form a volume of air therebetween; and a mechanical acoustic filter configured to be electrically controllable to change acoustic properties of the acoustic transducer, where the mechanical acoustic filter is formed by having at least one filter hole located in the membrane and/or having at least one filter hole located in a membrane support surrounding the membrane, and having at least one moveable portion of at least one blocking member located within the volume of air, where the at least one blocking member is electrically controllable, and where the at least one movable portion of the at least one blocking member is configured to selectively seal the at least one filter hole.

2. The acoustic transducer as claimed in claim 1 , wherein the transducer is a capacitive transducer comprising the membrane and the back plate.

3. The acoustic transducer as claimed in claim 1 , wherein the at least one blocking member comprises a resilient member biased in an open or blocking state.

4. The acoustic transducer as claimed in claim 1 , further comprising a blocking member actuator.

5. The acoustic transducer as claimed in claim 4 , wherein the blocking member actuator comprises at least one bias member, wherein the at least one bias member is configured to be electrically or electrostatically charged to attract or repel the blocking member.

6. The acoustic transducer as claimed in claim 1 , wherein the blocking member comprises at least one of the following: an anti-stick coating; and an anti-stick profile.

7. The acoustic transducer as claimed in claim 1 , wherein the electrically controllable mechanical acoustic filter changes the acoustic properties of the transducer.

8. The acoustic transducer as claimed in claim 1 , wherein the acoustic transducer comprises at least one of: a microphone; and a speaker.

9. An apparatus comprising: the acoustic transducer as claimed in claim 1 ; and a controller configured to control the mechanical acoustic filter.

10. The apparatus as claimed in claim 9 , further comprising a sensor configured to determine activity of the acoustic transducer, wherein the controller is further configured to control the mechanical acoustic filter dependent on a sensor value.

11. The apparatus as claimed in claim 9 , wherein the apparatus determines activity of the acoustic transducer; and electrically controls the mechanical acoustic filter to change the acoustic properties of the transducer dependent on the activity of the transducer.

12. The apparatus as claimed in claim 9 , wherein the controller is configured to control the mechanical acoustic filter in at least one of: a binary mode of control; a continuous mode of control; and a discrete stepwise control.

13. A method for an acoustic transducer comprising a membrane and a back plate configured to form a volume of air therebetween, the method comprising: electrically controlling a mechanical acoustic filter to change acoustic properties of the acoustic transducer, wherein the mechanical acoustic filter is formed by having at least one filter hole located in the membrane and/or having at least one filter hole located in a membrane support surrounding the membrane, and having at least one moveable portion of at least one blocking member located within the volume of air, where the at least one blocking member is electrically controllable, and where the at least one movable portion of the at least one blocking member is configured to selectively seal the at least one filter hole, and where electrically controlling the mechanical acoustic filter comprises electrically controlling the at least one blocking member within the volume of air to selectively seal the at least one filter hole.