Abstract: A noise suppression apparatus for an air handling unit includes an inlet section connectable to a fan of the air handling unit. The inlet section includes a forward wall spaced apart from an aft wall to define an internal chamber, and an inlet wall extending between the forward wall and the aft wall, the inlet wall defining an inlet air opening. A plurality of internal walls in the inlet wall define a plurality of resonator openings that each open to at least one of a plurality of resonator sections within the internal chamber. The plurality of resonator sections include at least one quarter wave tube section and at least one Helmholtz resonator section. One or more resonator sections are configured to attenuate noise generated by the fan at two or more frequencies. At least one resonator opening of the plurality of resonator openings opens to a plurality of resonator sections.

Abstract: Aspects of the present disclosure include a casing comprising an air inlet and an air outlet, a fan configured to move air from the air inlet to the air outlet, and a tunable sound attenuating module having an opening at a first end of the tunable sound attenuating module, a cavity, and a back wall at a second end of the tunable sound attenuating module, wherein: the tunable sound attenuating module is oriented such that the back wall is closer to the fan than the opening, and a length of tunable sound attenuating module is substantially one fourth of the acoustic wavelength of a sound generated by the fan.

Abstract: A noise suppression apparatus for an air handling unit includes an inlet section connectable to a fan of the air handling unit. The inlet section includes a forward wall spaced apart from an aft wall to define an internal chamber, and an inlet wall extending between the forward wall and the aft wall, the inlet wall defining an inlet air opening. A plurality of internal walls in the inlet wall define a plurality of resonator openings that each open to at least one of a plurality of resonator sections within the internal chamber. The plurality of resonator sections include at least one quarter wave tube section and at least one Helmholtz resonator section. One or more resonator sections are configured to attenuate noise generated by the fan at two or more frequencies. At least one resonator opening of the plurality of resonator openings opens to a plurality of resonator sections.

Abstract: A noise suppression apparatus for an air handling unit includes an inlet section connectable to a fan of the air handling unit. The inlet section includes a forward wall spaced apart from an aft wall to define an internal chamber, and an inlet wall extending between the forward wall and the aft wall, the inlet wall defining an inlet air opening. A plurality of internal walls in the inlet wall define a plurality of resonator openings that each open to at least one of a plurality of resonator sections within the internal chamber. The plurality of resonator sections include at least one quarter wave tube section and at least one Helmholtz resonator section. One or more resonator sections are configured to attenuate noise generated by the fan at two or more frequencies. At least one resonator opening of the plurality of resonator openings opens to a plurality of resonator sections.

Abstract: Aspects of the present disclosure include a casing comprising an air inlet and an air outlet, a fan configured to move air from the air inlet to the air outlet, and a tunable sound attenuating module having an opening at a first end of the tunable sound attenuating module, a cavity, and a back wall at a second end of the tunable sound attenuating module, wherein: the tunable sound attenuating module is oriented such that the back wall is closer to the fan than the opening, and a length of tunable sound attenuating module is substantially one fourth of the acoustic wavelength of a sound generated by the fan.