The protruding part of the rear cover is designed to fit into the depression of the
casing, in order to maintain the peripheral support condition. The product is designed so that the
resonance frequency determined by the peripheral support condition enables the optimum sound pressure
level to be obtained.
If the product is exposed to a higher temperature or for a longer time than our
stipulated soldering condition values (*), it is conceivable that the casing and the rear cover may
change in size, resulting in a change in the peripheral support condition of the diaphragm. If this
occurs, the resonance frequency will shift to a lower frequency, causing the frequency corresponding to
the sound pressure peak to fall.
In some cases, it may fall below the sound pressure level indicated in the delivery specifications for
the defined frequency (2khz, 4khz, etc.).