Acoustic transducer including airfoil for generating sound
View Patent ↗Systems, apparatus, devices, and methods for converting electrical signals into sound using an acoustic transducer. The inventive acoustic transducer utilizes the motion of an airfoil shaped element to generate a sound wave, with the airfoil element being driven in response to an electrical signal input to a suitable driving element. In some embodiments, the airfoil element or elements act to mechanically couple the motion of an armature attached to the driver to the surrounding air, producing sound waves in a more efficient manner than typical acoustic transducer devices. Embodiments of the invention may be used in the design of loudspeakers, earpieces, headphones, and other devices for which a high efficiency transducer is desired.
1. A transducer operative to generate an output acoustic wave, comprising:
a source of airflow having an outlet;
a plurality airfoil-shaped elements that are in line with one another, are spaced apart in fixed relation to one another, and connected in common with a bearing, the plurality of airfoil-shaped elements are movably positioned relative to the outlet so that air exiting the outlet flows predominantly along an upper camber surface of each airfoil-shaped element; and
a driver operative to rotate all of the plurality of airfoil-shaped elements in response to an input signal, thereby causing an angle of attack between a leading edge of all of the plurality of airfoil-shaped elements and the air exiting the outlet to vary in response to the input signal.
2. The transducer of claim 1 , wherein the source of airflow further comprises:
a structure having a shape that is substantially that of an airfoil, wherein all of the plurality of airfoil shaped elements rotate relative to the static structure in response to the input signal;
an air inlet through which air may be supplied to an interior chamber of the static structure; and
one or more vents, the vents providing an exit for air that is provided through the air inlet into the interior chamber of the structure, and the source of airflow comprises the air from the exit.
3. The transducer of claim 2 , wherein each airfoil-shaped element, the static structure, or both includes and extrusion length that is approximately five times its chord length.
4. The transducer of claim 1 , wherein the driver is a rotary voice coil.
5. The transducer of claim 1 , further comprising an element operative to provide a bias force in response to a rotation caused by the driver.
6. The transducer of claim 1 , wherein the input signal is the output of an amplifier, the output of a tuner, or the output of a MP3 decoder.
7. The transducer of claim 1 and further comprising: a spacer positioned between each of the plurality of airfoil-shaped elements.
8. The transducer of claim 1 , wherein each airfoil-shaped element has a thickness that is approximately 15% 20% of its chord length.
9. The transducer of claim 1 , wherein each airfoil-shaped element has a chord selected to provide a time for air to flow over the chord and the time is no more than approximately 5% of a period of a highest frequency of the transducer.
10. A system for producing an acoustic wave, comprising:
a source for an input signal;
a source of airflow having an outlet;
an airfoil-shaped element movably positioned relative to the outlet so that air exiting the outlet flows predominantly along an upper camber surface of the airfoil-shaped element;
a driver operative to rotate the airfoil-shaped element in response to the input signal, thereby causing an angle of attack between a leading edge of the airfoil-shaped element and the air exiting the outlet to vary in response to the input signal;
a static structure having a shape that is substantially that of an airfoil, wherein the airfoil shaped element rotates relative to the static structure in response to the input signal;
an air inlet through which air may be supplied to an interior chamber of the static structure; and
one or more vents, the vents providing an exit for air that is provided through the air inlet into the interior chamber of the structure, and the source of airflow comprises the air from the exit.
11. The system of claim 10 , wherein the source of the input signal is an amplifier, a tuner, or a MP3 decoder.
12. The system of claim 10 , wherein the driver is a rotary voice coil.
13. The system of claim 10 , further comprising an element operative to provide a bias force in response to a rotation caused by the driver.
14. The system of claim 13 , wherein the element operative to provide a bias force is a torsion spring.
15. A transducer operative to generate an output acoustic wave, comprising:
a driver;
an armature element coupled to the driver, the armature undergoing motion in response to the input signal being input to the driver; and
a plurality of airfoil-shaped elements coupled to the armature element and operative to move in response to the motion of the armature element,
wherein the plurality of airfoil-shaped elements are coupled to the armature element in a manner so as to generate a longitudinal sound wave as the armature element undergoes motion, and
wherein leading edges of the plurality of airfoil-shaped elements are positioned in opposing relation to each other and trailing edges of the plurality of airfoil-shaped elements are positioned in facing relation to each other.
16. The transducer of claim 15 , wherein the driver is a solenoid.
17. The transducer of claim 15 , wherein the motion comprises lateral motion and the armature is caused to move laterally in response to the input signal being input to the driver.
18. The transducer of claim 15 , wherein the motion comprises rotational motion and the armature is caused to rotate in response to the input signal being input to the driver.
19. The transducer of claim 15 , further comprising a source of the input signal.
20. The transducer of claim 19 , wherein the source of the input signal is an amplifier, a tuner, or a MP3 decoder.