An alarm (10; 10A; 10B), comprising: a sound outputter configured to generate a sound and a housing (50; 50A; 50B) in which the sound outputter is accommodated, the housing (50; 50A; 50B) including a first cover (60; 60B) having a front wall (61; 610) and a first peripheral wall (62; 620), the front wall (61; 610) including a shielding part (61c; 610c) having an airtight structure and covering the sound outputter, a second cover (70; 70A; 70B) having a rear wall (71; 71A; 710) and a second peripheral wall (72; 720), a plurality of supporting parts (86, 750), and one or more air passages (P11, P11A; P11B) configured to transmit the sound from the sound outputter via an opening (51; 510) at a location different from a location of the shielding part (61c; 610c) to an outside of the housing (50; 50A; 50B), characterized in that the plurality of supporting parts (86, 750) determine the distance between the front wall (61; 610) and the rear wall (71; 71A; 710), and the distance between the front wall (61; 610) and the rear wall (71; 71A; 710) and the dimensions of the first peripheral wall (62; 620) and the second peripheral wall (72; 720) are determined such that the first peripheral wall (62; 620) and the second peripheral wall (72; 720) do not come into contact with each other and the opening (51; 510) is formed between the first peripheral wall (62; 620) and the second peripheral wall (72; 720). a sound outputter configured to generate a sound and a housing (50; 50A; 50B) in which the sound outputter is accommodated, the housing (50; 50A; 50B) including a first cover (60; 60B) having a front wall (61; 610) and a first peripheral wall (62; 620), the front wall (61; 610) including a shielding part (61c; 610c) having an airtight structure and covering the sound outputter, a second cover (70; 70A; 70B) having a rear wall (71; 71A; 710) and a second peripheral wall (72; 720), a plurality of supporting parts (86, 750), and one or more air passages (P11, P11A; P11B) configured to transmit the sound from the sound outputter via an opening (51; 510) at a location different from a location of the shielding part (61c; 610c) to an outside of the housing (50; 50A; 50B), characterized in that a first cover (60; 60B) having a front wall (61; 610) and a first peripheral wall (62; 620), the front wall (61; 610) including a shielding part (61c; 610c) having an airtight structure and covering the sound outputter, a second cover (70; 70A; 70B) having a rear wall (71; 71A; 710) and a second peripheral wall (72; 720), a plurality of supporting parts (86, 750), and one or more air passages (P11, P11A; P11B) configured to transmit the sound from the sound outputter via an opening (51; 510) at a location different from a location of the shielding part (61c; 610c) to an outside of the housing (50; 50A; 50B), characterized in that the plurality of supporting parts (86, 750) determine the distance between the front wall (61; 610) and the rear wall (71; 71A; 710), and the distance between the front wall (61; 610) and the rear wall (71; 71A; 710) and the dimensions of the first peripheral wall (62; 620) and the second peripheral wall (72; 720) are determined such that the first peripheral wall (62; 620) and the second peripheral wall (72; 720) do not come into contact with each other and the opening (51; 510) is formed between the first peripheral wall (62; 620) and the second peripheral wall (72; 720).