Systems and methods for sensing an acoustic signal using microelectromechanical systems technology
An acoustic system has an acoustic sensor and a processing circuit. The acoustic sensor includes a base, a microphone having a microphone diaphragm supported by the base, and a hot-wire anemometer having a set of hot-wire extending members supported by the base. The set of hot-wire extending members defines a plane which is substantially parallel to the microphone diaphragm. The processing circuit receives a sound and wind pressure signal from the microphone and a wind velocity signal from the hot-wire anemometer, and provides an output signal based on the sound and wind pressure signal from the microphone and the wind velocity signal from the hot-wire anemometer (e.g., accurate sound with wind noise removed). The configuration of the hot-wire extending members defining a plane which is substantially parallel to the microphone diaphragm can be easily implemented in a MEMS device making the configuration suitable for miniaturized applications.
1. A method for providing an acoustic signal, the method comprising the steps of:
generating a sound and wind pressure signal in response to sound and wind pressure on a microphone diaphragm;
generating a wind velocity signal in response to wind velocity on a hot-wire anemometer having a set of hot-wire extending members that defines a plane which is substantially parallel to the microphone diaphragm; and
providing, as the acoustic signal, an output signal based on the generated sound and wind pressure signal and the generated wind velocity signal; wherein the step of providing the output signal includes the step of:
converting the wind velocity signal into an analog wind pressure signal having a wind pressure component, and
subtracting the wind pressure component of the analog wind pressure signal from the sound and wind pressure signal to provide the output signal.
2. The method of claim 1 , further comprising the step of:
providing, as the microphone and the hot-wire anemometer, a microelectromechanical systems device.
3. A method for providing an acoustic signal, the method comprising the steps of:
generating a sound and wind pressure signal in response to sound and wind pressure on a microphone diaphragm;
generating a wind velocity signal in response to wind velocity on a hot-wire anemometer having a set of hot-wire extending members that defines a plane which is substantially parallel to the microphone diaphragm; and
providing, as the acoustic signal, an output signal based on the generated sound and wind pressure signal and the generated wind velocity signal; wherein the step of providing the output signal includes the step of:
digitizing the wind velocity signal,
correlating the digitized wind velocity signal with a series of wind pressure values from a lookup table, and
subtracting the series of wind pressure values from the sound and wind pressure signal to provide the output signal.
4. A method for making a microelectromechanical systems device, the method comprising the steps of:
disposing a first layer of material over a base structure;
disposing a second layer of material over the first layer of materials; wherein the step of disposing the second layer of material includes a step of depositing, as the second layer of material, conductive material using a plasma enhanced chemical vapor deposition process; and wherein the step of depositing includes a step of positioning, as the conductive material, tungsten over the first layer of material such that the microelectromechanical systems device is capable of operating as a hot-wire anemometer; and
removing at least a portion of the first layer of material and a portion of the second layer of material such that a remainder of the second layer of material forms multiple extending members supported by the base structure, the extending members being parallel to each other, wherein each of the steps of disposing the first layer of material, disposing the second layer of material and removing occurs within a temperature range that is less than 700 degrees Celsius.
5. A method for making a microelectromechanical systems device, the method comprising the steps of:
disposing a first layer of material over a base structure;
disposing a second layer of material over the first layer of material; and
removing at least a portion of the first layer of material and a portion of the second layer of material such that a remainder of the second layer of material forms multiple extending members supported by the base structure, the extending members being parallel to each other, wherein each of the steps of disposing the first layer of material, disposing the second layer of material and removing occurs within a temperature range that is less than 700 degrees Celsius, wherein the base structure includes a substrate, and wherein the method further comprises the step of:
prior to disposing the first layer of material over the base structure, forming a microphone diaphragm over the substrate of the base structure such that, after the step of removing, the microphone diaphragm resides between the multiple extending members and the substrate.
6. The method of claim 5 , further comprising the step of:
removing a portion of the substrate to form a first portion of a condenser microphone cavity;
forming a rigid member over another substrate and removing a portion of the other substrate to form a second portion of the condenser microphone cavity; and
bonding the substrate with the other substrate such that the first and second portions of the condenser microphone cavity align, and such that the microphone diaphragm is disposed between the multiple extending members and the condenser microphone cavity to form, as the microelectromechanical systems device, an acoustic element having a hot-wire anemometer and a condenser microphone.