User Manual

Piezoelectric Polymer Speakers Application Note 1242138
Page 81
100 1000 10,000 100,000
FREQUENCY (Hz)
60
80
100
120
SPL (dB)
110
90
70
R=5cm
R=10cm
R=20cm
R=30cm
L=5cm W=5cm DISTANCE=1M
Figure 2
0
10 20 30 40
1000
2000
3000
4000
LOW FREQ CORNER (Hz)
RADIUS (cm)
0
10 20 30 40
RADIUS (cm)
75
80
85
90
95
100
SPL(dB)
Figure 3a Figure 3b
In the design of a piezo polymer speaker, the curvature of the film needs to be considered along with other
structural parameters. For example, for a small area speaker, especially with a short length L, a large radius
makes the film close to a flat plane, resulting in a lower acoustic output. On the other hand, for a large area
speaker, a small radius makes the speaker deeper which requires a larger space.
Changing the radius not only controls the cutoff frequency, but also affects the sound pressure level at certain
distances from the speaker. Figure 3a shows the relationship between low frequency corner and radius of
curvature. Figure 3b shows the relationship between SPL at 10 kHz and radius of curvature for the same
speaker. As seen from the graphs, the cutoff frequency and SPL are both inversely proportional to the radius.