Method and apparatus for minimizing or preventing interference of two-way radio speaker microphones caused by fine metal particles

A method of prolonging a functional lifespan of a speaker microphone in a two-way radio system against deteriorating effects of environmental fine metal particles, the method comprising:

• providing a speaker microphone having a casing with a front grille, and a speaker disposed within the casing;
• wherein the speaker has a flat diaphragm, a voice coil, a permanent magnet coupled to the diaphragm creating a magnetic gap, wherein the diaphragm is located between the magnet and the front grille;
• providing a first barrier cover between the front grille and the flat diaphragm and the first barrier cover is sealingly coupled to the flat diaphragm to create a closed chamber defined as a space between the flat diaphragm and the first barrier cover, wherein the closed chamber is airtight and is physically sealed to prevent entry of the plurality of fine metal particles into the closed chamber, and wherein the closed chamber is defined by the flat diaphragm on one side and the first barrier cover on the other side;
• physically preventing passage of a plurality of said fine metal particles therethrough;
• and
• wherein the first barrier cover is a comprised of one selected from a group consisting of a dome structure, a cone structure, and a short cylindrical structure;
• wherein the first barrier cover has a circular outer rim having a diameter Z, wherein diameter Z is equal to or less than 25 mm, and larger than the magnetic gap;
• wherein the diaphragm has a vibrating surface defined as a surface between its outer rim and where the diaphragm is attached to the voice coil;
• wherein the circular outer rim of the first barrier cover is attached directly on the vibrating surface.