Integrated electroacoustic transducer

An electroacoustic transducer formed within a semiconductor substrate comprising:

• a diaphragm which vibrates in response to an input signal at audio and/or ultrasonic frequencies;
• a pair of electrodes placed with respect to said diaphragm so that the electric field between the electrodes varies in relation to the vibrating diaphragm to permit conversion between electrical and acoustic signals, the electrodes defining an air gap therebetween;
• and
• acoustic venting means comprising a continuous array of small holes extending through one of the electrodes to the air gap, said array covering essentially the entire area of that electrode which is co-extensive with the diaphragm, where the density of the holes in the array is at least 50 per mm.sup.2 and the diameter of the holes is less than 100 .mu.m.

An electroacoustic transducer formed within a semiconductor substrate comprising:

• a diaphragm which vibrates in response to an input signal at audio and/or ultrasonic frequencies;
• a front acoustic cavity defined by a portion of the semiconductor substrate adjacent to the diaphragm;
• a pair of electrodes placed with respect to said diaphragm so that the electric field between the electrodes varies in relation with the vibrating diaphragm to permit conversion between electrical and acoustic signals and so that an air gap is formed between the electrodes;
• a back acoustic cavity adjacent to one of the electrodes and defined by a member which also shields the transducer from electromagnetic interference;
• acoustic venting means comprising an array of holes connecting the air gap to the back acoustic cavity;
• and
• an acoustic port defined by an element adjacent to the front acoustic cavity, the size of the port being such as to produce a desired frequency response characteristic for the transducer.