Piezoelectric speaker
AssigneeMatsushita Electric Industrial Co., Ltd.
InventorShoji Nakajima
Life of this patent
Estimating the term…
Abstract
A piezoelectric speaker having a flat and stable output vs. frequency characteristic attained by coupling a damping ring to an annular ring-shaped area surrounded by two nodal lines at the first overtone of a piezoelectric vibrator. The vibrator has concentric nodal lines at a resonance and vibrates in a planar bending vibration mode. The central part of a conical-shaped diaphragm is coupled to the piezoelectric vibrator and is accommodated in a housing. An acoustic resistive material is coupled between the piezoelectric vibrator and the inner bottom surface of the housing.
Claims10
A piezoelectric speaker comprising
- a piezoelectric vibrator having first and second opposite surfaces, said vibrator vibrating in a planar bending mode so as to define a pair of spaced concentric nodal lines located on the first surface of said vibrator at the first overtone thereof;
- a damping ring having a mass which is not greater than one-third of the mass of said piezoelectric vibrator affixed to the first surface of said vibrator only in the annular space between said first and second concentric nodal lines, said damping ring dampening vibrations at said first overtone;
- a conical diaphragm having a central part thereof affixed to the central portion of the first surface of said vibrator, the part of said diaphragm affixed to said vibrator being surrounded by said damping ring;
- a housing surrounding said piezoelectric vibrator, damping ring and conical diaphragm;
- and
- an acoustic resistive member attached to said housing and the second surface of said piezoelectric vibrator for supporting said vibrator, said acoustic resistive member having a diameter nearly equal to the diameter of the smaller of said nodal lines.
Dependencies are inferred from the claim text.