Please select the most similar patent number from A, B, C and D. Which number is?
Noise-reduction bricks having a bell mouth, each brick comprising a brick body (1). One bottom surface of the brick body (1) is concave inward to form a bell shape; the thin end of a bell mouth (2) is connected to a sound absorption cavity (3); sound absorption cotton (4) is placed in the sound absorption cavity (3); and a reflection cover (5) is arranged at the bell mouth (2). Each brick is an independent noise-reduction unit, and the bricks are combined by means of bricklaying to build sound-absorbing wall surfaces or sound-absorbing buildings. The noise-reduction bricks having a bell mouth have a simple structure and good sound absorption and noise reduction effects.
A: Provided is a sound absorption plate with a unit structure. The sound absorption plate comprises an ultramicropore sound absorption panel (1), a side plate (2) and a sound absorption back plate (3). The edge parts of the ultramicropore sound absorption panel (1) are connected with the sound absorption back plate (3) through the side plate (2) and thus form a sound absorption resonant cavity (4). The material of the ultramicropore sound absorption panel (1) is a metal material carrying nano microspheres (5). A sound absorption metal thin film (6) carrying nano microspheres (5), parallel to the ultramicropore sound absorption panel, is arranged inside the sound absorption resonant cavity (4). A pore size of the nano microspheres in the ultramicropore sound absorption panel (1) and the sound absorption metal thin film (6) is 100-1000 nm. The sound absorption plate has a simple structure, simple and convenient manufacture and assembly, a wide sound absorption band and a good noise reduction effect, and is suitable for ceiling and wall decorations of buildings.
B: Dust pretreatment equipment for grab ship unloading in a port, comprising a hopper (1). A feed pipe (2) is fixedly connected to the bottom of the hopper (1); a sliding groove (3) is fixedly connected to one side of the hopper (1); a slider (4) is slidably connected in the sliding groove (3); a bell mouth (5) is mounted at the top of the slider (4); an air inlet pipe (6) is fixedly connected to the bell mouth (5); a fan (7) is fixedly connected to one end of the air inlet pipe (6); the fan (7) is fixedly mounted at one side of the hopper (1); an air outlet pipe (8) is fixedly connected to one side of the fan (7); a dust collection box (9) is fixedly connected to one end of the air outlet pipe (8). In the equipment, a gear (11) works in conjunction with a rack (10), such that the slider (4) and the bell mouth (5) can be pushed to slide back and forth, and the dust floating on the hopper (1) can be absorbed by means of the bell mouth (5); the equipment is convenient and effective.
C: A vacuum pump having a good noise reduction effect, comprising a casing body (1). A sound insulation plate (2) is fixedly connected to an inner wall of the casing body (1); a sound absorbing cover (3) is provided penetrating through the right side of the casing body (1); springs (4) are fixedly connected to two sides of the bottom of the inner cavity of the sound insulation plate (2); tops of the springs (4) are fixedly connected to a movable plate (5); a connecting plate (6) is provided on the top of the movable plate (5); a pump body (7) is fixedly connected to the top of the connecting plate (6); an oil cavity (8) is fixedly connected to the bottom of the inner cavity of the sound insulation plate (2); by means of the cooperation of the casing body (1), the sound insulation plate (2), the sound absorbing cover (3), the springs (4), the movable plate (5), the connecting plate (6), the pump body (7), the oil cavity (8), a piston rod (9), a connecting rod (10) and a connecting block (11), the vacuum pump achieves the purpose of a good noise reduction effect, is capable of effectively carrying out noise reduction on noise generated by the vacuum pump, avoids troubles to users, improves the experience of the users to the vacuum pump, satisfies demands of the market today, improves the practicability and usability of the vacuum pump, and solves the problem of a poor noise reduction effect of conventional vacuum pumps.
D: A device capable of bringing stimulation by means of blow and suction comprises an enclosed hood (1). A hood boy opening used for being in contact with a human body is formed in the bottom end of the enclosed hood (1). A control circuit board (2) is disposed in the enclosed hood (1). A vibration horn (3) is electrically connected to the control circuit board (2). The mouth of the vibration horn (3) is open to the hood boy, and an air blowing channel (4) is formed between the mouth and the hood boy. The control circuit board (2) can be connected to a power supply to connect a sound source circuit to drive the vibration horn (3) to vibrate and to form an air flow in the air blowing channel (4). By using the device capable of bringing stimulation by means of blow and suction, when the vibration horn (3) vibrates, a volume-variable cavity is formed, so that the human body in the enclosed hood (1) is in an environment in which a negative pressure and a positive pressure fast alternates, and an erogenous zone more easily engorges with blood. In addition, the vibration horn (3) is used as a main driving component, the vibration stroke and frequency of the vibration horn (3) can be conveniently adjusted by means of audio, and accordingly, the change frequency and the change extent of an air pressure and an air flow in each of the enclosed hood (1) and the air blowing channel (4) can be adjusted.
Answer: A