Abstract: An arrangement for attenuating noise in an air handling unit having a forwardly curved centrifugal fan and dampers downstream of the fan for varying the volume rate of air flow. The dampers are located downstream of the fan a distance L which is about 30 inches so that the critical acoustical frequency f=C/4L is relatively high (125 Hz). The discharge section of the air handling unit between the fan and the dampers is lined on the sides with acoustical panels that are effective in absorbing sound at the critical frequency.

Abstract: A slot diffuser is utilized to counteract large heat losses through a wall or window by producing a vertical blanket or curtain of air adjacent the wall or window. An elongate housing defines a plenum chamber delivering air to a uniquely constructed convergent-divergent diffuser slot. High velocity air exits from the diffuser slot and is rapidly intermixed with the induced cold air from the wall or window. The rapid mixing, resulting from the high discharge velocity, permits very hot air to be introduced into the room, yielding a high induction ratio so that a small volume of air counteracts a high rate of heat leakage. The specially shaped diffuser slot performs relatively noiselessly while permitting high velocity air to flow therethrough.