Techniques for generating audio signals
Techniques described herein generally relate to generating an audio signal with a speaker. In some examples, a speaker device is described that includes a membrane and a shutter. The membrane can be configured to oscillate along a first directional path and at a first frequency effective to generate an ultrasonic acoustic signal. The shutter can be positioned about the membrane and configured to modulate the ultrasonic acoustic signal such that an audio signal can be generated.
1. A speaker apparatus, comprising:
a membrane element configured to move along a first direction to generate a first wave with a frequency within a first range of frequencies;
a shutter element; and
a spacer element, coupled to the membrane element and to the shutter element, to separate the membrane element from the shutter element,
wherein the shutter element at least partially defines a waveguide, between the membrane element and the shutter element, through which the first wave propagates along the first direction from the membrane element to the shutter element, and
wherein the shutter element is configured to operate on the first wave to produce a second wave with a frequency within a second range of frequencies.
2. The speaker apparatus of claim 1 , wherein the second range of frequencies includes an audio frequency range, and wherein the first range of frequencies includes an ultrasonic frequency range.
3. The speaker apparatus of claim 1 , wherein to operate on the first wave, the shutter element is configured to move along a second direction different from the first direction as the first wave is incident on the shutter element.
4. The speaker apparatus of claim 1 , wherein the shutter element is configured with at least one opening, wherein to operate on the first wave, the shutter element is configured to move between a first position and a second position, and wherein the speaker apparatus further comprises:
a blind element configured with at least one opening,
wherein at the first position of the shutter element, the at least one opening of the shutter element is aligned with the at least one opening of the blind element, to enable the first wave to pass through both the at least one opening of the shutter element and the at least one opening of the blind element, and
wherein at the second position of the shutter element, the at least one opening of the shutter element is misaligned with the at least one opening of the blind element, to cover at least a portion of either or both the at least one opening of the shutter element and the at least one opening of the blind element.
5. The speaker apparatus of claim 4 , wherein the membrane element, the shutter element, and the blind element are arranged in respective planes that are parallel to each other.
6. The speaker apparatus of claim 1 , wherein to operate on the first wave, the shutter element is configured to move as the first wave is incident on the shutter element, and wherein the speaker apparatus further comprises at least one controller coupled to the membrane element and to the shutter element to control movement of the membrane element and the shutter element.
7. The speaker apparatus of claim 1 , wherein the second range of frequencies is lower than the first range of frequencies.
8. A speaker apparatus, comprising:
a first element configured to receive electrostatic actuation to oscillate at a first frequency to generate a first wave; and
a second element configured as a shutter that moves at a second frequency different from the first frequency,
wherein the first wave generated by the first element is incident on the second element, and
wherein the movement of the second element enables the second element to operate as the shutter on the first wave to generate a second wave.
9. The speaker apparatus of claim 8 , wherein the second wave includes a frequency within an audio frequency range, and wherein the first wave includes a frequency within an ultrasonic frequency range.
10. The speaker apparatus of claim 8 , wherein the second element is spaced apart from the first element, and wherein the first element and the second element are arranged in parallel respective planes.
11. The speaker apparatus of claim 8 , wherein the second element is configured with at least one opening, and wherein the speaker apparatus further includes a third element configured to at least partially cover and reveal the at least one opening of the second element as the second element moves.
12. The speaker apparatus of claim 11 , wherein the third element is located between the first element and the second element.
13. The speaker apparatus of claim 11 , wherein the third element is located above the first element and the second element.
14. The speaker apparatus of claim 8 , wherein the first element and the second element comprise parts of a microelectromechanical system (MEMS) speaker device, and wherein the speaker apparatus further comprises a computer device coupled to the MEMS speaker device and that includes at least one controller configured to generate at least one control signal to respectively control the oscillation of the first element and the movement of the second element.
15. A method to manufacture a microelectromechanical system (MEMS) speaker device, the method comprising:
forming a membrane element that is configured to oscillate at a first frequency to generate a first wave;
forming a shutter element that is configured to move at a second frequency different from the first frequency; and
spacing the shutter element apart from the membrane element to at least partially define a waveguide between the spaced apart shutter and membrane elements, to enable the generated first wave to propagate within the waveguide from the membrane element to the shutter element,
wherein the movement of the shutter element enables the shutter element to operate on the generated first wave to generate a second wave.
16. The method of claim 15 , wherein the second wave includes a frequency with an audio frequency range, and wherein the first wave includes a frequency with an ultrasonic frequency range.
17. The method of claim 15 , wherein the membrane element is configured to oscillate along a first direction, and wherein the shutter element is configured to move along a second direction different from the first direction.
18. The method of claim 15 , wherein the shutter element is configured to move between a first position and a second position, and wherein a distance between the first position and the second position is equal to a distance between two consecutive openings of the shutter element.
19. The method of claim 15 , wherein a frequency of the first wave is different from a frequency of the second wave.
20. The method of claim 17 , further comprising:
forming blind element that is configured to at least partially cover and reveal at least one opening of the shutter element as the shutter element moves in the second direction.