Tone generator

In a sound generator unit of the type having a casing provided with a closed primary sound cavity and a secondary sound cavity separated by a diaphragm, an electromagnetic driver mounted in said secondary sound cavity having a diaphragm actuating element disposed in front of and spaced from said diaphragm and operative to vibrate the same, improved means for mounting said diaphragm and sealing said closed primary sound cavity, said means providing opposed surfaces engaging the peripheral marginal portion of said diaphragm at opposite sides thereof with one of said surfaces being firm and hard and the other of said surfaces being flexible and resilient, said means further providing a substantially tight air seal at the periphery of said closed primary sound cavity relative to the rapid air movements within said closed primary sound cavity caused by the vibration of said diaphragm while permitting relatively slow air leakage into and out of said closed primary sound cavity so that the steady-state pressure differential across said diaphragm is substantially equalized.

The method of maintaining an essentially uniform tone quality under normal conditions of use in a toner generator of the type having a housing provided with a closed primary sound cavity and a secondary sound cavity wherein the two cavities are separated by a diaphragm that is adapted to be vibrated at a predetermined frequency by the pole piece of an electromagnetic coil assembly disposed in said secondary sound cavity, said method comprising the steps of establishing and maintaining a desired loudness characteristic for said tone by supporting and positioning said diaphragm and said electromagnetic coil assembly in said housing on respective fixed reference surfaces spaced with respect to each other to provide an air gap of predetermined dimension between said pole piece and said diaphragm;

• and maintaining a desired pitch characteristic for said tone by holding said electromagnetic coil assembly firmly against its reference surface while yieldably urging the peripheral marginal portion only of said diaphragm against its reference surface under pressure sufficient to effectively seal said primary sound cavity when air in said cavity is moved rapidly by vibration of said diaphragm in use but insufficient to prevent slow leakage of air when the pressure differential across said diaphragm changes as a result of variations in ambient temperature or pressure.

The method of maintaining an essentially uniform tone quality in a tone generator of the type having a housing provided with a closed primary sound cavity and a secondary sound cavity separated by a diaphragm which is adapted to be vibrated by the pole piece of an electromagnetic coil mounted on a circuit board disposed in said secondary sound cavity comprising the steps of seating said circuit board and the peripheral marginal portion of said diaphragm on respective reference surfaces in said housing spaced precisely to establish an air gap of predetermined dimensions between said pole piece and said diaphragm to establish and maintain a desired loudness characteristic for said tone;

• and firmly holding said circuit board against its reference surface while yieldably urging the peripheral marginal portion of said diaphragm against its reference surface by an annular resilient gasket under pressure sufficient to seal said primary sound cavity under normal conditions of use but insufficient to prevent air leakage past the periphery of said diaphragm due to changes in pressure differential across said diaphragm as a result of varying conditions of ambient temperature and pressure.

In a sound generator of the type having a housing provided with a closed primary sound cavity and a secondary sound cavity separated by a diaphragm and electromagnetic means having a mounting portion and a pole piece for vibrating said diaphragm, the improvement comprising means providing a pair of fixed reference surfaces spaced a predetermined distance apart in said housing, one of said reference surfaces seating the peripheral marginal portion of said diaphragm and the other of said reference surfaces seating the mounting portion of said electromagnetic means, said reference surfaces supporting said diaphragm and said electromagnetic means with said pole piece disposed to vibrate said diaphragm and spaced precisely therefrom a predetermined distance;

• means holding the mounting portion of said electromagnetic means firmly against said other reference surface;
• and means yieldingly urging the peripheral marginal portion of said diaphragm against said one reference surface under pressure sufficient to seal said primary sound cavity under normal conditions of use but insufficient to prevent leakage of air past the periphery of said diaphragm due to changes in pressure differential across said diaphragm as a result of varying conditions of ambient temperature and pressure.

In a sound generator for automotive vehicles of the type having a casing housing a diaphragm, electromagnetic means for vibrating said diaphragm, and circuit means for energizing said electromagnetic means, the improvement wherein a portion of said casing and said diaphragm cooperatively define a closed sound cavity, and comprising means mounting said diaphragm in said casing including a pair of diaphragm retaining members at opposite sides of and in engagement with the peripheral marginal portion of said diahragm, one of said members being resilient and the other of said members being firm and unyielding, and means holding said diaphragm retaining members and said diaphragm together with said resilient one member compressed, said resilient one member exerting sufficient pressure against said diaphragm by reason of its compressed condition to seal said cavity under relatively stable conditions of atmospheric temperature and pressure normally encountered in the use of said vehicle but yieldable when atmospheric conditions change relatively rapidly to permit slow leakage of air to or from said cavity so that the cavity pressure at one side of the diaphragm can substantially equalize with atmospheric pressure at the other side of the diaphragm to prevent objectionable change in the tone produced by said generator.