Vibration characterization of analog microelectromechanical microphone systems operating in air and vacuum

Microelectromechanical microphone systems are acoustic sensors that can be mass-produced by taking advantage of advances in silicon fabrication technology. These devices come in different sizes and types and are used extensively in a vast number of mobile devices, such as mobile phones and hearing aid devices. Especially in devices that combine microphones with vibrating transducers, it is important that their response to different types of vibrations is known. As newer microphones have lighter diaphragms they are relatively insensitive to vibration. This fact poses the problem in measuring their response to vibration as the microphone will be much more sensitive to the excited sound from the vibration rather than the vibration per se. We tackle this issue by using a reference microphone to measure the relative response with the device under test prior to the vibration measurement. We use this to later on subtract the voltage response related to sound capturing from the induced vibration. In our differential measurement method we apply harmonic excitation to an analog microelectromechanical microphone system and quantify the effect of vibration and sound transmission comparing our measurements in open air and vacuum. Our setup does not require specially designed fixtures and uses standard equipment, making it easier to implement and obtain results from.