MEMS enable Sensors for sound Actuators to create sound Integrated electronics for processing sound signals Carrying out the necessary computations

Transcription

1 Acoustic MEMS Presented to Proficience #33 class in Jan.-May term of 2005 Lecture 6b G. K. Ananthasuresh Mechanical Engineering Indian Institute of Science Bangalore, INDIA March 12 th,

2 2 MEMS and Acoustics MEMS enable Sensors for sound Actuators to create sound Integrated electronics for processing sound signals Carrying out the necessary computations Acoustics can use Micro microphones Microspeakers Integrated circuits for signal processing The computing power integrated with the sensor and actuator

3 3 Micromachined microphones This basic design can be easily implemented at the micro scale. Could be very cost-effective and possibly compete with macro microphones. Are definitely useful in array-applications (e.g., surveillance, acoustic imaging)

4 4 Piezoresistive silicon microphone Typical sensitivity: 25 uv/pa Frequency response: 100 Hz 5 KHz (Schellin and Hess, 1992)

5 5 Piezoelectric microphone Typical sensitivity: uv/pa Frequency response: 10 Hz 10 KHz Royer et al. (1983)

6 6 Capacitive microphones Scheeper et al., 1994

7 7 Moving gate FET microphone Kuhnel (1991) Sensitivity: mv/pa Frequency range: 100 Hz 30 KHz

8 8 Microspeakers Magnetic actuation Polymer membrane. Glass and silicon substrates. Cheng et al., 2004

9 9 CMOS-MEMS micromachined earphone Neumann and Gabriel, 2002 Frequency range: 40 Hz 10 KHz Polymer membrane integrated with CMOS.

10 10 Polymer micro loudspeaker Heydt et al., 1999 Electrostrictive polymer film (EPF) is used. Light-wieght Flat-panel loudspeaker Active noise control for panels

11 11 Micro loudspeakers for hearing-impaired Rehder et al., 1999 Magnetic actuation 5x5x2 mm 3 Better frequency range. Easy manufacture and low cost. Could be used in an array more easily. Could be integrated with on-chip circuitry.

12 12 One more hearing-aid speaker Harradine et al., 1997 Smaller size is more attractive in view of increased concealment. Less problems with acoustic feedback. Lower current increases battery life.

13 13 A few recent developments in acoustic applications of MEMS

14 14 Acoustic impedance control Polymer balloon actuators Yoda and Konishi, 2002

15 15 A MEMS-based sound intensity probe Tuzzo, et al., 9 th AIAA/CEAS Aeroacoustics Conference, May12-14, 2003, HH, SC. Solves the spatial resolution problem in p-p technique.

16 16 Digital reconstruction of sound using MEMS Analog Advantages of DRS: Large dynamic range is not necessary. Digital Nonlinearity can be controlled distortion is minimized. Fault tolerance. Intensity control. Speaklets are combined to produce the sound effect. With low-pass filters, the sound is smoothened. Diamond et al., 2003

17 17 DRS prototype 8-bit speaker array containing 255 square membranes, each 216 um on a side. Total chip area is 5.2 mm x 5.2 mm Diamond et al., 2003

18 18 Active noise control in flat panels Could be micromachined. An array could be used instead of one big actuator. Zhu et al., JASA, 11392), 2003

19 19 Acoustic wave based sensors Kovacs, 2001

20 20 Main points Possibly MEMS enable us to play with sound in as many ways as playing with light Microphones, microspeakers, and signal processing are within the reach Newer materials and processing techniques need can be tapped for novel devices Finding newer ways to manipulate sound is the key Arrays, integrated electronics, lower cost are the winning points at the microscale