An earphone device (100; 100A; 100B; 100C; 100D; 100E; 100F; 100G) connected to a source of sound signal (40; 40A; 40B; 40C; 40D; 100Ga, 100Gb) for sending out sound into at least one external ear of a human being, comprising: a signal-to-sound converter (25; 25A; 25C; 25D; 25E; 25F; 25G) converting a sound signal to internal sound; an ear coupler (10; 10A; 10C; 10D; 10E; 10F; 10G) engaged with said at least one external ear of said human being, and formed with a first sound propagation path open at one end thereof to said at least one external ear so that external sound and said internal sound are sent out into said external ear of said human being; and a sound tube (20; 200; 201; 202; 203; 204; 205; 206; 207; 208; 20B; 20C; 20D; 20E; 20F; 20G) connected between said signal-to-sound converter (25; 25A; 25C; 25D; 25E; 25F; 25G) and said ear coupler (10; 10A; 10C; 10D; 10E; 10F; 10G), and formed with a second sound propagation path (20b; 200b; 201c; 202b; 203a; 204c; 205b; 206b; 207b; 208b) connected at one end thereof to the other end of said first sound propagation path and at the other end thereof to said signal-to-sound converter (25; 25A; 25C; 25D; 25E; 25F; 25G) so that said internal sound is propagated from said signal-to-sound converter (25; 25A; 25C; 25D; 25E; 25F; 25G) to said first sound propagation path, characterized in that said sound tube (20; 200; 201; 202; 203; 204; 205; 206; 207; 208; 20B; 20C; 20D; 20E; 20F; 20G) is further formed with an external sound entrance (20c; 200c; 201a; 202a; 203b; 204a; 205a; 206a; 207a; 208a) open at one end thereof to environment and at the other end thereof to said second sound propagation path (20b; 200b; 201c; 202b; 203a; 204c; 205b; 206b; 207b; 208b), said earphone device (100; 100A; 100B; 100C; 100D; 100E; 100F; 100G) further comprising an active valve unit (21; 210; 211; 212; 214; 215; 216; 217; 218; 21B; 21C; 21D; 21E; 21F; 21G) supported by said sound tube (20; 200; 201; 202; 203; 204; 205; 206; 207; 208; 20B; 20C; 20D; 20E; 20F; 20G) and responsive to voltage supplied from a source (30b, 34; 30Ab, 41; 30b, 34; 30C, 34C; 30Db, 34D; 25Fc, 34F; 100Ga, 34G) of voltage so as to be deformed for closing said external sound entrance (20c; 200c; 201 a; 202a; 203b; 204a; 205a; 206a; 207a; 208a) therewith and permitting said environment to be conducted to said second sound propagation path (20b; 200b; 201c; 202b; 203a; 204c; 205b; 206b; 207b; 208b) through said external sound entrance (20c; 200c; 201 a; 202a; 203b; 204a; 205a; 206a; 207a; 208a), and an electric coupling (L2; L3, L4; EM; L2, L6; L7; L8) connected to said active valve unit (21; 210; 211; 212; 214; 215; 216; 217; 218; 21B; 21C; 21 D; 21 E; 21 F; 21G) and supplying said voltage to said active valve unit (21; 210; 211; 212; 214; 215; 216; 217; 218; 21B; 21C; 21D; 21E; 21F; 21G). a signal-to-sound converter (25; 25A; 25C; 25D; 25E; 25F; 25G) converting a sound signal to internal sound; an ear coupler (10; 10A; 10C; 10D; 10E; 10F; 10G) engaged with said at least one external ear of said human being, and formed with a first sound propagation path open at one end thereof to said at least one external ear so that external sound and said internal sound are sent out into said external ear of said human being; and a sound tube (20; 200; 201; 202; 203; 204; 205; 206; 207; 208; 20B; 20C; 20D; 20E; 20F; 20G) connected between said signal-to-sound converter (25; 25A; 25C; 25D; 25E; 25F; 25G) and said ear coupler (10; 10A; 10C; 10D; 10E; 10F; 10G), and formed with a second sound propagation path (20b; 200b; 201c; 202b; 203a; 204c; 205b; 206b; 207b; 208b) connected at one end thereof to the other end of said first sound propagation path and at the other end thereof to said signal-to-sound converter (25; 25A; 25C; 25D; 25E; 25F; 25G) so that said internal sound is propagated from said signal-to-sound converter (25; 25A; 25C; 25D; 25E; 25F; 25G) to said first sound propagation path, characterized in that said sound tube (20; 200; 201; 202; 203; 204; 205; 206; 207; 208; 20B; 20C; 20D; 20E; 20F; 20G) is further formed with an external sound entrance (20c; 200c; 201a; 202a; 203b; 204a; 205a; 206a; 207a; 208a) open at one end thereof to environment and at the other end thereof to said second sound propagation path (20b; 200b; 201c; 202b; 203a; 204c; 205b; 206b; 207b; 208b), said earphone device (100; 100A; 100B; 100C; 100D; 100E; 100F; 100G) further comprising an active valve unit (21; 210; 211; 212; 214; 215; 216; 217; 218; 21B; 21C; 21D; 21E; 21F; 21G) supported by said sound tube (20; 200; 201; 202; 203; 204; 205; 206; 207; 208; 20B; 20C; 20D; 20E; 20F; 20G) and responsive to voltage supplied from a source (30b, 34; 30Ab, 41; 30b, 34; 30C, 34C; 30Db, 34D; 25Fc, 34F; 100Ga, 34G) of voltage so as to be deformed for closing said external sound entrance (20c; 200c; 201 a; 202a; 203b; 204a; 205a; 206a; 207a; 208a) therewith and permitting said environment to be conducted to said second sound propagation path (20b; 200b; 201c; 202b; 203a; 204c; 205b; 206b; 207b; 208b) through said external sound entrance (20c; 200c; 201 a; 202a; 203b; 204a; 205a; 206a; 207a; 208a), and an electric coupling (L2; L3, L4; EM; L2, L6; L7; L8) connected to said active valve unit (21; 210; 211; 212; 214; 215; 216; 217; 218; 21B; 21C; 21 D; 21 E; 21 F; 21G) and supplying said voltage to said active valve unit (21; 210; 211; 212; 214; 215; 216; 217; 218; 21B; 21C; 21D; 21E; 21F; 21G).