Acoustic transducer with balanced properties

An acoustic transducer for converting electric signals into mechanical vibrations on acoustic frequencies, the acoustic transducer comprising:

• an upper part and a lower part;
• a first permanent magnet located in the upper part and a second permanent magnet located in the lower part, with magnetic poles of the same name of the first and second permanent magnets facing each other in the direction of an axis line;
• an upper cover in the upper part and a lower cover in the lower part, said upper and lower covers comprising magnetic material and together defining an enclosure around the first and second permanent magnets;
• and
• at least one coil located in said enclosure and configured to create, under influence of an electric current flowing through said coil, dynamic magnetic forces in the direction of said axis line;
• wherein a separating gap between edges of said upper cover and lower cover is directed essentially in the direction of said axis line, allowing a relative movement of the edges of said lower cover and said upper cover in the direction of said axis line between different positions, said positions differing in the extent to which said edges of said upper cover and lower cover coincide in the directiokn perpendicular to said axis line;
• wherein said lower cover has a U-formed cross section, with said second permanent magnet located inside the loop of the U-formed cross section;
• wherein said upper cover has a plate-formed cross section, with an outer edge of the plate defining said edge of the upper cover;
• and
• wherein said first permanent magnet is on that side of the plate that faces the inside of the U-formed cross section of the lower cover.

An arrangement for producing sound, the arrangement comprising:

• an electronic device with first and second structural parts;
• at least one acoustic transducer comprising,
• an upper part and a lower part;
• a first permanent magnet located in the upper part and a second permanent magnet located in the lower part, with same named magnetic poles of the first and second permanent magnets facing each other in the direction of an axis line;
• an upper cover in the upper part and a lower cover in the lower part, said upper and lower covers comprising magnetic material and together defining an enclosure around the first and second permanent magnets;
• and
• at least one coil located in said enclosure and configured to create, under influence of an electric current flowing through said coil, dynamic magnetic forces in the direction of said axis line;
• wherein a separating gap between edges of said upper cover and lower cover is directed essentially in the direction of said axis line, allowing a relative movement of the edges of said lower cover and said upper cover in the direction of said axis line between different positions, said positions differing in the extent to which said edges of said upper cover and lower cover coincide in the direction perpendicular to said axis line;
• wherein said upper cover has a U-formed cross section, with said first permanent magnet located inside the loop of the U-formed cross section;
• wherein said lower cover has a plate-formed cross section, with an outer edge of the plate defining said edge of the lower cover;
• wherein said second permanent magnet is on that side of the plate that faces the inside of the U-formed cross section of the upper cover;
• and
• wherein the upper part of the acoustic transducer is attached to said first structural part and the lower part of the acoustic transducer is attached to said second structural part of the electronic device;
• and
• as part of the electronic device an electric circuit configured to feed electric signals into said at least one coil of the at least one acoustic transducer.

An arrangement for producing sound, the arrangement comprising:

• an electronic device with first and second structural parts;
• at least one acoustic transducer comprising,
• an upper part and a lower part;
• a first permanent magnet located in the upper part and a second permanent magnet located in the lower part, with same named magnetic poles of the first and second permanent magnets facing each other in the direction of an axis line;
• an upper cover in the upper part and a lower cover in the lower part, said upper and lower covers comprising magnetic material and together defining an enclosure around the first and second permanent magnets;
• and
• at least one coil located in said enclosure and configured to create, under influence of an electric current flowing through said coil, dynamic magnetic forces in the direction of said axis line;
• wherein a separating gap between edges of said upper cover and lower cover is directed essentially in the direction of said axis line, allowing a relative movement of the edges of said lower cover and said upper cover in the direction of said axis line between different positions, said positions differing in the extent to which said edges of said upper cover and lower cover coincide in the direction perpendicular to said axis line;
• wherein said lower cover has a U-formed cross section, with said second permanent magnet located inside the loop of the U-formed cross section;
• said upper cover has a plate-formed cross section, with an outer edge of the plate defining said edge of the upper cover;
• and
• said first permanent magnet is on that side of the plate that faces the inside of the U-formed cross section of the lower cover;
• wherein the upper part of the acoustic transducer is attached to said first structural part and the lower part of the acoustic transducer is attached to said second structural part of the electronic device;
• and
• as part of the electronic device an electric circuit configured to feed electric signals into said at least one coil of the at least one acoustic transducer.