一、压电陶瓷扬声器Piezoelectric ceramic speaker
Fig.2.12. It is one kind Piezoelectric ceramic speaker of improvement middle and low frequency.It is composed of three piezoelectric ceramic vibrators 5 and a piezoelectric ceramic vibrator 6. The piezoelectric ceramic vibrator 5 of diameter is 21 mm, the diameter of 6 is 27 mm, 3- the piezoelectric ceramic disk , 4-the vibration disk, and the diameter is 50 mm. 1 is the paper cone vibration plate edge portions of 4 and a frame of 2 connected with an opening edge.
The structure of speaker, the audio signal input the first and second piezoelectric ceramic vibrators o 5 and 6 at the same time, so that the bending vibration is the same of phase, It will drive vibration plate 4 to produce a larger amplitude, as shown in Fig.2.12 (b) the distance of the dashed and solid lines.
Fig.2.13 shown the frequency response characteristics for this kind of piezoelectric ceramic speaker; Dash line is the piezoelectric ceramic loudspeaker characteristic curve for the single structure.
Seen by the graph, the frequency range of piezoelectric ceramic speaker within the scope of 100-5000Hz, there is the enough sound pressure level of sound reproduction, the sound pressure level is Special obvious in the low-frequency range.
二、压电陶瓷受话器Piezoelectric ceramic receiver
It has received attention because the advantage of piezoelectric ceramic receiver there is light weight, no electromagnetic interference (EMI) characteristics etc, the product has good moisture resistance, used in lightweight diving communication equipment mainly. Fig.2.19, it is composed of three degrees of freedom sound vibration. 1- the vibration plate, its edge on the inner frame 2: the edge of metal is fixed and bonded by electric conduction paste between the piezoelectric ceramic disk and the thin metal disk. Then the receiver chamber is divided into: 5-the first front air chamber and 6-the first behind air chamber, 7-the second front the air chamber( headphones ) and the first front air chamber 5 connected by 3-the sound hole, the first behind air chamber and the outside space connected by damping hole. When the AC signal input through 8- the terminal wire, the vibration will generate the stretching vibration with an external signal, the generating sound pressure level was leaded through the second front air chamber, So we can hear the sound.
The frequency response characteristics as shown in Fig.2.20, the solid line is no reveal, the point line is close to the ear, the pressure is 700g, the dotted line is close to the ear, the pressure is 200g.